Epoxy resin containing dynamic covalent bonds and synthesis method thereof, and preparation method of self-repairing epoxy structure adhesive

Abstract

The invention discloses epoxy resin containing dynamic covalent bonds, a synthesis method of the epoxy resin and a preparation method of a self-repairing epoxy structure adhesive, and belongs to the field of self-repairing structure adhesives. The specific scheme is as follows: the self-repairing epoxy structure adhesive comprises epoxy resin containing dynamic disulfide bonds, commercial epoxy resin, a carboxylic acid curing agent containing dynamic disulfide bonds, a functionalized rubber toughening agent, functionalized graphene oxide nanosheets, a thermoplastic resin toughening agent and a transesterification agent. The self-repairing epoxy structure adhesive is prepared by physical mixing of hot melting blending, grinding dispersion and vacuum stirring. The preparation method comprises the following steps: firstly, synthesizing three epoxy resins containing dynamic disulfide bonds and a carboxylic acid compound containing dynamic disulfide bonds; the self-repairing epoxy structure adhesive with high bonding strength and high repairing efficiency is prepared by controlling the structure and proportion of the dynamic disulfide bond-containing epoxy resin, the structure and proportion of the dynamic disulfide bond-containing carboxylic acid curing agent and the particle size and proportion of the thermoplastic polyester.

Description

Technical Field

[0001] The present invention belongs to the field of self-repairing structural adhesives, and in particular relates to an epoxy resin containing dynamic covalent bonds, a synthesis method thereof, and a preparation method of the self-repairing epoxy structural adhesive. Background Art

[0002] With the rapid development of aerospace technology, the aerospace sector is placing higher demands on new and intelligent materials. Structural adhesives are a class of interface materials capable of transmitting large static and dynamic loads. Aerospace structural adhesives also possess properties such as heat resistance, weather resistance, and high strength. They play a crucial role in providing efficient, simplified, and reliable manufacturing methods for the integrated molding of multifunctional components, complex structures, and large structures. Currently, the use of structural adhesives as a bonding medium for disparate components has gained widespread acceptance among advanced materials manufacturers and researchers. However, traditional organic structural adhesives are susceptible to internal fatigue and external stresses during application, resulting in mechanical damage that can compromise the performance and service life of bonded components. In particular, subtle microscopic damage can pose a significant potential threat to the safety of components and even the entire aircraft. Mechanical damage is typically addressed through emergency field repairs or factory repairs of bonded components. Conventional repair techniques have significant limitations, and directly replacing entire components can significantly increase costs. Furthermore, in space, repairs are difficult or even impossible.

[0003] The emergence of self-repairing technology has brought a new idea for solving the above problems. The self-repairing structural adhesive designed and prepared based on dynamic covalent bonds can realize in-situ repair of damaged bonded structural parts, self-repair of microcracks, remote repair and multiple efficient repairs. The self-repaired bonded structural parts have high strength, avoiding time-consuming, labor-intensive and costly repair processes such as patching and replacing damaged components. It can solve the remote repair of damaged components of space aircraft, and has huge development prospects and application value in important engineering and cutting-edge fields such as aerospace. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art that epoxy structural adhesives cannot self-repair or have low self-repair efficiency, few repair times, and poor bonding strength after repair, and further provide an epoxy resin containing dynamic covalent bonds and a synthesis method thereof, as well as a preparation method of a self-repairing epoxy structural adhesive.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An epoxy resin containing dynamic covalent bonds, wherein the epoxy resin containing dynamic covalent bonds is an epoxy resin containing dynamic disulfide bonds, and the epoxy resin molecules containing dynamic disulfide bonds include epoxy resins represented by structural formula I, structural formula II, or structural formula III:

[0007]

[0008] A method for synthesizing an epoxy resin containing dynamic covalent bonds comprises the following steps:

[0009] Add epichlorohydrin, deionized water, and ethylene glycol to a four-necked flask equipped with a stirrer, condenser, dropping funnel, and nitrogen atmosphere. Heat in an oil bath at 40-60°C. Add bis(4-hydroxyphenyl) disulfide in 3-5 portions. After addition, control the temperature of the reaction system at 50-70°C and react for 1-2 hours. Then, add chloroform and continue stirring for 4-8 hours. Lower the temperature to 30-50°C and slowly and uniformly add a 30%-50% aqueous solution of NaOH by weight. Maintain the temperature for 60-150 minutes. After the reaction is completed, the reaction mixture is cooled to room temperature and chloroform is added to a four-necked flask. The reaction solution is transferred to a separatory funnel and washed with deionized water for 3 to 5 times. After standing for separation, the lower layer solution is taken into a beaker, anhydrous MgSO4 is added, and stirred for 1 to 3 hours. The MgSO4 is removed by filtration, and the solvent is distilled off. The product is separated and purified by silica gel column chromatography using dichloromethane as the eluent. The eluent is distilled off and vacuum dried for 12 to 24 hours to obtain an epoxy resin containing dynamic disulfide bonds, as shown in structural formula I. Bis(2-hydroxyethyl) disulfide is replaced by bis(4-hydroxyphenyl) disulfide, and the above preparation is repeated to obtain an epoxy resin containing dynamic disulfide bonds as shown in structural formula II. 1,1'-disulfadiylbis(2, The above preparation is repeated to obtain an epoxy resin containing dynamic disulfide bonds as shown in structural formula III; wherein the molar ratio of bis(4-hydroxyphenyl) disulfide, bis(2-hydroxyethyl) disulfide and 1,1'-dithiodiylbis(2,2,6,6-tetramethylpiperidin-4-ol) to epichlorohydrin is 1:1; epichlorohydrin, deionized water and ethylene glycol are mixed in any proportion; the ratio of epichlorohydrin to NaOH aqueous solution is 1 mol:150-200 ml; the ratio of chloroform to epichlorohydrin added twice is 2 ml-5 ml:1 ml; and the ratio of epichlorohydrin to MgSO4 is 1 ml:2 g-5 g.

[0010] A method for preparing a self-healing epoxy structural adhesive. The components of the self-healing epoxy structural adhesive include an epoxy resin containing dynamic disulfide bonds, a commercial epoxy resin, a carboxylic acid curing agent containing dynamic disulfide bonds, a functionalized rubber toughening agent, functionalized graphene oxide nanosheets, a thermoplastic resin toughening agent, and an ester exchange agent. The self-healing epoxy structural adhesive is prepared by physical mixing through hot melt blending, grinding and dispersion, and vacuum kneading. The epoxy resin containing dynamic disulfide bonds includes the epoxy resins represented by structural formulas I, II, and III.

[0011] Furthermore, the mass ratio of the epoxy resin containing dynamic disulfide bonds represented by structural formula I, structural formula II and structural formula III is 100:5-15:10-20.

[0012] Furthermore, the commercial epoxy resin includes bisphenol A epoxy resin (E51) and brominated epoxy resin, and the mass ratio of bisphenol A epoxy resin (E51) to brominated epoxy resin is 100:5-10. The mass ratio of the commercial epoxy resin to the epoxy resin containing dynamic disulfide bonds is 5-20:100.

[0013] Furthermore, the carboxylic acid curing agent containing a dynamic disulfide bond includes substances represented by structural formula IV to structural formula VI:

[0014]

[0015] The value of n ranges from 3 to 5.

[0016] Furthermore, the mass ratio of the carboxylic acid curing agents containing dynamic disulfide bonds represented by structural formula IV, structural formula V, and structural formula VI is 100:10-30:5-10.

[0017] Furthermore, the functionalized rubber toughening agent is a butadiene-acrylonitrile rubber containing epoxy groups, and the amount used is 1%-3% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0018] Furthermore, the functionalized graphene oxide nanosheets are amino-functionalized graphene oxide nanosheets, and the amount used is 0.5%-1.0% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0019] Furthermore, the thermoplastic resin toughening agent is a micro-powdered thermoplastic polyester having two particle sizes, one with a particle size range of 20 to 50 μm and the other with a particle size range of 80 to 170 μm, and the mass ratio of the two particle sizes of thermoplastic polyester is 10 to 25:100.

[0020] Furthermore, the melting range of the micro-powdered thermoplastic polyester is 115°C to 140°C.

[0021] Furthermore, the mass ratio of the micro-powdered thermoplastic polyester to the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin is 40 to 65:100. A portion of the micro-powdered thermoplastic polyester is dispersed in the self-healing epoxy structural adhesive by vacuum kneading and exists in the form of micro-powder solid.

[0022] Furthermore, the molar ratio of epoxy groups to carboxyl groups in the formula of the self-repairing epoxy structural adhesive is 1.06-1.10:1.

[0023] Furthermore, the transesterification agent is one or a mixture of triphenylphosphine, zinc acetylacetonate, dibutyltin oxide, tributyltin chloride titanium isopropoxide, butyl titanate, and dichlorotitanocene.

[0024] Furthermore, the amount of the transesterification agent used is 0.5% to 5% of the molar amount of epoxy groups in the self-repairing epoxy structural adhesive formula.

[0025] Furthermore, the synthesis method of the carboxylic acid curing agent IV containing a dynamic disulfide bond comprises the following steps:

[0026] Under nitrogen protection, 4,4'-diaminodiphenyl disulfide is dissolved in chloroform in a three-necked flask, wherein the mass volume ratio of 4,4'-diaminodiphenyl disulfide to chloroform is 1 g / 10-20 ml, and the mixture is stirred at 40-60° C. for 30-60 min. Acrylic acid is added dropwise, wherein the molar ratio of 4,4'-diaminodiphenyl disulfide to acrylic acid is 1:2. After the addition of acrylic acid, the mixture is stirred in the dark at 40-60° C. for 15-30 h. After distilling off the solvent, the product is separated and purified by silica gel column chromatography using chloroform as the eluent. After distilling off the eluent, the dynamic disulfide bond-containing carboxylic acid curing agent IV is obtained.

[0027] Furthermore, the self-repairing epoxy structural adhesive is prepared by a physical mixing method of hot melt blending, grinding dispersion, and vacuum kneading, and the specific steps are as follows:

[0028] (1) Preparation of hot melt blends

[0029] 10% to 15% of the total mass of a thermoplastic polyester with a particle size range of 20 to 50 μm and 5% to 10% of the total mass of a thermoplastic polyester with a particle size range of 80 to 170 μm are uniformly mixed with a bisphenol A epoxy resin (E51), and the mixture is melted and stirred in a hot melt reactor heated by circulating oil until the thermoplastic polyester is completely melted in the bisphenol A epoxy resin (E51), thereby forming a uniform and transparent hot melt blend A. The temperature of the blend is maintained at 150 to 180°C.

[0030] (2) Preparation of rubber-toughened epoxy resin

[0031] Three epoxy resins containing dynamic disulfide bonds and a functionalized rubber toughening agent were added to a single-necked flask containing ethyl acetate, stirred at room temperature until they were completely dissolved to form a uniform system, and the ethyl acetate was removed by rotary distillation to obtain a rubber toughened epoxy resin B.

[0032] (3) Preparation of grinding dispersion resin

[0033] A rubber-toughened epoxy resin B, a carboxylic acid curing agent IV containing dynamic disulfide bonds, functionalized graphene oxide nanosheets, and an ester exchange agent are mixed to form a crude mixture C. The crude mixture C is ground and dispersed 3 to 5 times on a ceramic three-roll mill to obtain a ground and dispersed resin D. The roller surface temperature of the three-roll mill is controlled within a range of 25 to 60°C.

[0034] Hot melt blend A is preheated in a forced air drying oven at 60-90°C for 120-180 minutes. A vacuum kneader is heated to 50-70°C for 120-180 minutes. The preheated hot melt blend A, rubber-toughened epoxy resin B, ground and dispersed resin D, remaining thermoplastic polyester, carboxylic acid curing agents V and VI containing dynamic disulfide bonds, and brominated epoxy resin are added to the preheated vacuum kneader and kneaded under vacuum for 10-30 minutes to produce a self-healing epoxy structural adhesive. The material temperature is controlled between 50-80°C and the vacuum level is controlled between -0.098 MPa and -0.095 MPa.

[0035] The resulting self-healing epoxy structural adhesive was used to bond aluminum alloy single lap shear test pieces, with the adhesive layer thickness controlled at 0.1-0.3 mm. The pieces were cured in an oven at 150-170°C for 2-5 hours. After cooling naturally to room temperature, the bonded pieces were removed for tensile shear testing and the shear strength was calculated. The two test pieces were then placed face-to-face with the adhesive-attached side, and a pressure of 0.1-0.5 MPa was applied. The pieces were then repaired in an oven at 150-170°C for 3-6 hours. After cooling naturally to room temperature, the bonded pieces were removed for tensile shear testing and the shear strength of the repaired pieces was calculated.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention first synthesizes three epoxy resins containing dynamic disulfide bonds and a carboxylic acid compound containing dynamic disulfide bonds. By controlling the structure and ratio of the epoxy resins containing dynamic disulfide bonds, the structure and ratio of the carboxylic acid curing agent containing dynamic disulfide bonds, and the particle size and ratio of the thermoplastic polyester, a self-healing epoxy structural adhesive with high bonding strength and high repair efficiency is prepared. The present invention designs and synthesizes epoxy resins containing dynamic disulfide bonds and carboxylic acid compound molecules containing dynamic disulfide bonds, introduces dynamic disulfide bonds into the molecular structures of epoxy resins and curing agents, and gives the adhesive system intrinsic self-healing characteristics; ester bonds are generated by the curing reaction between carboxylic acid compounds and epoxy resins, and polar covalent bonds are beneficial to improving the bonding performance. At the same time, the ester bonds also act as a dynamic covalent bond to synergize with the dynamic disulfide bonds to reduce the exchange activation energy of the dynamic covalent bonds of the adhesive during the repair process, further improving the self-healing efficiency; the introduction of thermoplastic polyester into the adhesive system has a dual effect. First, the thermoplastic polyester micropowder can in situ toughen the adhesive and improve the bonding strength of the adhesive. Second, the thermoplastic polyester itself can also be used as a repair agent for epoxy structural adhesives, which can not only complete the repair of larger cracks, but also further improve the repair efficiency of the self-healing adhesive; the combination and synergistic effect of the above three design ideas jointly give the self-healing epoxy structural adhesive of the present invention high repair efficiency and multiple self-healing characteristics. Furthermore, the synergistic effect of functionalized rubber and functionalized graphene oxide enhances the toughness and bulk strength of the self-healing epoxy structural adhesive, further improving its bonding strength. The resulting self-healing epoxy structural adhesive exhibits high bonding performance and multiple, efficient self-healing properties, with a shear strength of ≥28 MPa, a shear strength repair efficiency of ≥90%, and a shear strength of ≥25.2 MPa after repair.

[0038] Figures in the specification

[0039] Figure 1 The H NMR spectrum of the epoxy resin molecular structure I with dynamic disulfide bonds;

[0040] Figure 2 Schematic diagram of the dynamic exchange of disulfide and ester bonds. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention.

[0042] Example 1

[0043] A method for preparing a self-healing epoxy structural adhesive. The components of the self-healing epoxy structural adhesive include an epoxy resin containing dynamic disulfide bonds, a commercial epoxy resin, a carboxylic acid curing agent containing dynamic disulfide bonds, a functionalized rubber toughening agent, functionalized graphene oxide nanosheets, a thermoplastic resin toughening agent, and an ester exchange agent. The self-healing epoxy structural adhesive is prepared by a physical mixing method including hot melt blending, grinding and dispersion, and vacuum kneading. The epoxy resin containing dynamic covalent bonds is an epoxy resin containing dynamic disulfide bonds. The epoxy resin molecules containing dynamic disulfide bonds include epoxy resins represented by structural formulas I, II, and III:

[0044]

[0045] Furthermore, the mass ratio of the epoxy resins containing dynamic disulfide bonds represented by Structural Formula I, Structural Formula II, and Structural Formula III is 100:5:10.

[0046] Furthermore, the commercial epoxy resin includes bisphenol A epoxy resin (E51) and brominated epoxy resin, wherein the mass ratio of bisphenol A epoxy resin (E51) to brominated epoxy resin is 100:5. The mass ratio of the commercial epoxy resin to the dynamic disulfide bond epoxy resin is 5:100.

[0047] Furthermore, the dynamic disulfide bond-containing carboxylic acid curing agent includes substances represented by structural formula IV to structural formula VI:

[0048]

[0049] The value of n is 3.

[0050] Furthermore, the mass ratio of the carboxylic acid curing agents containing dynamic disulfide bonds represented by Structural Formula IV, Structural Formula V, and Structural Formula VI is 100:10:5.

[0051] Furthermore, the functional rubber toughening agent is a nitrile rubber containing epoxy groups, and the amount used is 1% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0052] Furthermore, the functionalized graphene oxide nanosheets are amino-functionalized graphene oxide nanosheets, and the amount used is 0.5% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0053] Furthermore, the thermoplastic resin toughening agent is a micro-powdered thermoplastic polyester having two particle sizes, one with a particle size range of 20 to 50 μm and the other with a particle size range of 80 to 170 μm, and the weight ratio of the two particle sizes of thermoplastic polyester is 10:100.

[0054] Furthermore, the melting range of the micro-powdered thermoplastic polyester is 115°C to 120°C.

[0055] Furthermore, the mass ratio of the micro-powdered thermoplastic polyester to the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin is 40:100.

[0056] Furthermore, the molar ratio of epoxy groups to carboxyl groups in the self-healing epoxy structural adhesive formula is 1.06:1.

[0057] Furthermore, the transesterification agent is triphenylphosphine, and the amount of the transesterification agent used is 0.5% of the molar amount of epoxy groups in the self-repairing epoxy structural adhesive formula.

[0058] Furthermore, the synthesis of the epoxy resin containing dynamic disulfide bonds comprises the following steps:

[0059] Epichlorohydrin, deionized water, and ethylene glycol were added to a four-necked flask equipped with a stirrer, condenser, dropping funnel, and nitrogen atmosphere. Heat in an oil bath at 40°C. Bis(4-hydroxyphenyl) disulfide was added in three portions. After the addition, the temperature of the reaction system was controlled at 50°C and allowed to react for 1 hour. Chloroform was then added and the reaction was continued with stirring for 4 hours. The temperature was then lowered to 30°C, and a 30% aqueous solution of NaOH was slowly and uniformly added dropwise. The temperature was then maintained for 60 minutes. After the reaction is completed, the reaction mixture is cooled to room temperature and chloroform is added to a four-necked flask. The reaction solution is transferred to a separatory funnel and washed with deionized water three times. After standing for stratification, the lower layer solution is taken into a beaker, anhydrous MgSO4 is added, and stirred for 1 hour. MgSO4 is removed by filtration, and the solvent is distilled off. The product is separated and purified by silica gel column chromatography, using dichloromethane as the eluent. After the eluent is distilled off, the product is vacuum-dried for 12 hours to obtain an epoxy resin containing dynamic disulfide bonds, as shown in structural formula I. The hydrogen nuclear magnetic spectrum shows that the epoxy resin molecular structural formula I is an epoxy resin containing dynamic disulfide bonds, as shown in Figure 1 shown.

[0060] By replacing bis(4-hydroxyphenyl) disulfide with bis(2-hydroxyethyl) disulfide and repeating the above preparation steps, the epoxy resin containing dynamic disulfide bonds prepared is shown in structural formula II; by replacing bis(4-hydroxyphenyl) disulfide with 1,1'-disulfadiylbis(2,2,6,6-tetramethylpiperidin-4-ol) and repeating the above preparation steps, the epoxy resin containing dynamic disulfide bonds prepared is shown in structural formula III. Among them, the molar ratio of bis(4-hydroxyphenyl) disulfide, bis(2-hydroxyethyl) disulfide and 1,1'-dithiodiylbis(2,2,6,6-tetramethylpiperidin-4-ol) to epichlorohydrin is 1:1; epichlorohydrin, deionized water and ethylene glycol are mixed in any proportion; the ratio of epichlorohydrin to NaOH aqueous solution is 1 mol:150 ml; the ratio of chloroform added twice to epichlorohydrin is 2 ml:1 ml; the ratio of epichlorohydrin to MgSO4 is 1 ml:2 g.

[0061] Furthermore, the synthesis method of the carboxylic acid curing agent IV containing a dynamic disulfide bond comprises the following steps:

[0062] Under nitrogen protection, 4,4'-diaminodiphenyl disulfide was dissolved in chloroform in a three-necked flask, wherein the mass volume ratio of 4,4'-diaminodiphenyl disulfide to chloroform was 1 g / 10 ml, and the mixture was stirred at 40°C for 30 min. Acrylic acid was added dropwise, wherein the molar ratio of 4,4'-diaminodiphenyl disulfide to acrylic acid was 1:2. After the addition of acrylic acid, the mixture was stirred in the dark at 40°C for 15 h. After distilling off the solvent, the product was separated and purified by silica gel column chromatography using chloroform as the eluent. After distilling off the eluent, a dynamic disulfide bond-containing carboxylic acid curing agent IV was obtained.

[0063] Furthermore, the self-repairing epoxy structural adhesive is prepared by a physical mixing method of hot melt blending, grinding dispersion, and vacuum kneading, and the specific steps are as follows:

[0064] (1) Preparation of hot melt blends

[0065] 10% by weight of a thermoplastic polyester with a particle size range of 20 to 50 μm and 5% by weight of a thermoplastic polyester with a particle size range of 80 to 170 μm were uniformly mixed with a bisphenol A epoxy resin (E51). The mixture was melted and stirred in a hot melt reactor heated by circulating oil until the thermoplastic resin was completely melted in the bisphenol A epoxy resin (E51), forming a uniform and transparent hot melt blend A. The temperature of the blend was maintained at 160°C.

[0066] (2) Preparation of rubber-toughened epoxy resin

[0067] The epoxy resin containing dynamic disulfide bonds and the functionalized rubber toughening agent were added to a single-necked flask containing ethyl acetate, stirred at room temperature until they were completely dissolved to form a uniform system, and the ethyl acetate was removed by rotary distillation to obtain the rubber toughened epoxy resin B.

[0068] (3) Preparation of grinding dispersion resin

[0069] A rubber-toughened epoxy resin B, a carboxylic acid curing agent IV containing dynamic disulfide bonds, amino-functionalized graphene oxide nanosheets, and an ester exchange agent were mixed to form a crude mixture C. The crude mixture C was then ground and dispersed three times on a ceramic three-roll mill to obtain a ground and dispersed resin D. The roller surface temperature of the three-roll mill was controlled at 25°C.

[0070] (4) The hot melt blend A is preheated in a blast drying oven at 60°C for 120 minutes, and the vacuum kneader is set to 50°C for 120 minutes. The preheated hot melt blend A, rubber toughened epoxy resin B, ground dispersed resin D, remaining thermoplastic polyester, carboxylic acid curing agents V and VI containing dynamic disulfide bonds, and brominated epoxy resin are added to the preheated vacuum kneader and vacuum kneaded for 30 minutes to obtain a self-healing epoxy structural adhesive. The material temperature is controlled at 50°C and the vacuum degree is controlled at -0.098 MPa.

[0071] The resulting self-healing epoxy structural adhesive was used to bond aluminum alloy single lap shear test specimens with a 0.1mm adhesive layer thickness. The specimens were cured in a 150°C oven for 5 hours. After cooling to room temperature, the bonded specimens were removed for tensile shear testing and the shear strength was calculated. The two specimens were then bonded face-to-face with the adhesive-attached side. A pressure of 0.1 MPa was applied and the specimens were repaired in a 150°C oven for 3 hours. After cooling to room temperature, the specimens were removed for tensile shear testing and the shear strength of the repaired specimens was calculated.

[0072] The self-repairing epoxy structural adhesive prepared by the above steps contains double dynamic covalent bonds, and the exchange of double dynamic covalent bonds occurs during the repair process, such as Figure 2 The self-healing epoxy structural adhesive has the advantages of high bonding performance and multiple efficient self-repairing. Its shear strength is 28.4 MPa, the shear strength repair efficiency is 90%, and the shear strength after repair is 25.6 MPa.

[0073] Example 2

[0074] A method for preparing a self-healing epoxy structural adhesive. The components of the self-healing epoxy structural adhesive include an epoxy resin containing dynamic disulfide bonds, a commercial epoxy resin, a carboxylic acid curing agent containing dynamic disulfide bonds, a functionalized rubber toughening agent, functionalized graphene oxide nanosheets, a thermoplastic resin toughening agent, and an ester exchange agent. The self-healing epoxy structural adhesive is prepared by a physical mixing method including hot melt blending, grinding and dispersion, and vacuum kneading. The epoxy resin containing dynamic covalent bonds is an epoxy resin containing dynamic disulfide bonds. The epoxy resin molecules containing dynamic disulfide bonds include epoxy resins represented by structural formulas I, II, and III:

[0075]

[0076]

[0077] Furthermore, the mass ratio of the epoxy resins containing dynamic disulfide bonds represented by Structural Formula I, Structural Formula II, and Structural Formula III is 100:15:20.

[0078] Furthermore, the commercial epoxy resin includes bisphenol A epoxy resin (E51) and brominated epoxy resin, wherein the mass ratio of bisphenol A epoxy resin (E51) to brominated epoxy resin is 100:10. The mass ratio of the commercial epoxy resin to the dynamic disulfide bond epoxy resin is 20:100.

[0079] Furthermore, the dynamic disulfide bond-containing carboxylic acid curing agent includes substances represented by structural formula IV to structural formula VI:

[0080]

[0081] The value of n is 5.

[0082] Furthermore, the mass ratio of the carboxylic acid curing agents containing dynamic disulfide bonds represented by structural formula IV, structural formula V, and structural formula VI is 100:30:10.

[0083] Furthermore, the functional rubber toughening agent is a nitrile rubber containing epoxy groups, and the amount used is 3% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0084] Furthermore, the functionalized graphene oxide nanosheets are amino-functionalized graphene oxide nanosheets, and the amount used is 1.0% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0085] Furthermore, the thermoplastic resin toughening agent is a micro-powdered thermoplastic polyester having two particle sizes, one with a particle size range of 20 to 50 μm and the other with a particle size range of 80 to 170 μm, and the weight ratio of the two particle sizes of thermoplastic polyester is 25:100.

[0086] Furthermore, the melting range of the micro-powdered thermoplastic polyester is 125°C to 140°C.

[0087] Furthermore, the mass ratio of the micro-powdered thermoplastic polyester to the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin is 65:100.

[0088] Furthermore, the molar ratio of epoxy groups to carboxyl groups in the self-healing epoxy structural adhesive formula is 1.10:1.

[0089] Furthermore, the transesterification agent is zinc acetylacetonate.

[0090] Furthermore, the amount of the transesterification agent used is 5% of the molar amount of epoxy groups in the self-repairing epoxy structural adhesive formula.

[0091] Furthermore, the synthesis of the epoxy resin containing dynamic disulfide bonds comprises the following steps:

[0092] Epichlorohydrin, deionized water, and ethylene glycol were added to a four-necked flask equipped with a stirrer, condenser, dropping funnel, and nitrogen atmosphere. Heat in an oil bath at 60°C. Bis(4-hydroxyphenyl) disulfide was added in five portions. After the addition, the temperature of the reaction system was controlled at 70°C and allowed to react for 2 hours. Chloroform was then added and the reaction continued with stirring for 8 hours. The temperature was then lowered to 50°C, and a 50% aqueous solution of NaOH was slowly and uniformly added dropwise. The temperature was then maintained for 150 minutes. After the reaction is completed, the reaction mixture is cooled to room temperature and chloroform is added to a four-necked flask. The reaction solution is transferred to a separatory funnel and washed with deionized water 5 times. After standing for stratification, the lower layer solution is taken into a beaker, anhydrous MgSO4 is added, and stirred for 3 hours. MgSO4 is removed by filtration, and the solvent is distilled off. The product is separated and purified by silica gel column chromatography, using dichloromethane as the eluent. The eluent is distilled off and vacuum dried for 24 hours to obtain an epoxy resin containing dynamic disulfide bonds, as shown in structural formula I. Bis(2-hydroxyethyl) disulfide is replaced by bis(4-hydroxyphenyl) disulfide, and the above preparation steps are repeated to obtain an epoxy resin containing dynamic disulfide bonds as shown in structural formula II. 1,1'-disulfadiylbis( The above preparation steps are repeated to prepare an epoxy resin containing dynamic disulfide bonds as shown in structural formula III, wherein the molar ratio of bis(4-hydroxyphenyl) disulfide, bis(2-hydroxyethyl) disulfide and 1,1'-dithiodiylbis(2,2,6,6-tetramethylpiperidin-4-ol) to epichlorohydrin is 1:1; epichlorohydrin, deionized water and ethylene glycol are mixed in any proportion; the ratio of epichlorohydrin to NaOH aqueous solution is 1 mol:200 ml; the ratio of chloroform to epichlorohydrin added twice is 5 ml:1 ml; and the ratio of epichlorohydrin to MgSO4 is 1 ml:5 g.

[0093] Furthermore, the synthesis method of the carboxylic acid curing agent IV containing a dynamic disulfide bond comprises the following steps:

[0094] Under nitrogen protection, 4,4'-diaminodiphenyl disulfide was dissolved in chloroform in a three-necked flask, wherein the mass volume ratio of 4,4'-diaminodiphenyl disulfide to chloroform was 1 g / 20 ml, and the mixture was stirred at 60°C for 60 min. Acrylic acid was added dropwise, wherein the molar ratio of 4,4'-diaminodiphenyl disulfide to acrylic acid was 1:2. After the addition of acrylic acid, the mixture was stirred in the dark at 60°C for 30 h. After distilling off the solvent, the product was separated and purified by silica gel column chromatography using chloroform as the eluent. After distilling off the eluent, a dynamic disulfide bond-containing carboxylic acid curing agent IV was obtained.

[0095] Furthermore, the self-repairing epoxy structural adhesive is prepared by a physical mixing method of hot melt blending, grinding dispersion, and vacuum kneading, and the specific steps are as follows:

[0096] (1) Preparation of hot melt blends

[0097] 15% of the total mass of a thermoplastic polyester having a particle size range of 20 to 50 μm and 10% of the total mass of a thermoplastic polyester having a particle size range of 80 to 170 μm were uniformly mixed with a bisphenol A epoxy resin (E51), and the mixture was melted and stirred in a hot melt reactor heated by circulating oil until the thermoplastic resin was completely melted in the bisphenol A epoxy resin (E51), thereby forming a uniform and transparent hot melt blend A. The temperature of the blend was maintained at 180°C.

[0098] (2) Preparation of rubber-toughened epoxy resin

[0099] The epoxy resin containing dynamic disulfide bonds and the functionalized rubber toughening agent were added to a single-necked flask containing ethyl acetate, stirred at room temperature until they were completely dissolved to form a uniform system, and the ethyl acetate was removed by rotary distillation to obtain the rubber toughened epoxy resin B.

[0100] (3) Preparation of grinding dispersion resin

[0101] A rubber-toughened epoxy resin B, a carboxylic acid curing agent IV containing dynamic disulfide bonds, amino-functionalized graphene oxide nanosheets, and an ester exchange agent were mixed to form a crude mixture C. The crude mixture C was then ground and dispersed five times on a ceramic three-roll mill to obtain a ground and dispersed resin D. The roller surface temperature of the three-roll mill was controlled at 60°C.

[0102] (4) The hot melt blend A is preheated in a blast drying oven at 90°C for 180 minutes. The vacuum kneader is heated at 70°C for 180 minutes. The preheated hot melt blend A, rubber toughened epoxy resin B, ground dispersed resin D, remaining thermoplastic polyester, carboxylic acid curing agents V and VI containing dynamic disulfide bonds, and brominated epoxy resin are added to the preheated vacuum kneader and vacuum kneaded for 10 minutes to obtain a self-healing epoxy structural adhesive. The material temperature is controlled at 80°C and the vacuum degree is controlled at -0.095 MPa.

[0103] The resulting self-healing epoxy structural adhesive was used to bond aluminum alloy single lap shear test specimens with a bondline thickness of 0.003 mm. The specimens were cured in a 170°C oven for 2 hours. After cooling to room temperature, the bonded specimens were removed for tensile shear testing and the shear strength was calculated. The two specimens were then bonded face-to-face with the adhesive-attached side. A pressure of 0.5 MPa was applied and the specimens were repaired in a 1170°C oven for 6 hours. After cooling to room temperature, the specimens were removed for tensile shear testing and the shear strength of the repaired specimens was calculated.

[0104] The self-healing epoxy structural adhesive prepared by the above steps contains double dynamic covalent bonds, and the exchange of double dynamic covalent bonds occurs during the repair process. The self-healing epoxy structural adhesive has the advantages of high bonding performance and multiple efficient self-repair. Its shear strength is 29.2MPa, the shear strength repair efficiency is 92%, and the shear strength after repair is 26.9MPa.

[0105] Example 3

[0106] A method for preparing a self-healing epoxy structural adhesive. The components of the self-healing epoxy structural adhesive include an epoxy resin containing dynamic disulfide bonds, a commercial epoxy resin, a carboxylic acid curing agent containing dynamic disulfide bonds, a functionalized rubber toughening agent, functionalized graphene oxide nanosheets, a thermoplastic resin toughening agent, and an ester exchange agent. The self-healing epoxy structural adhesive is prepared by a physical mixing method including hot melt blending, grinding and dispersion, and vacuum kneading. The epoxy resin containing dynamic covalent bonds is an epoxy resin containing dynamic disulfide bonds. The epoxy resin molecules containing dynamic disulfide bonds include epoxy resins represented by structural formulas I, II, and III:

[0107]

[0108] Furthermore, the mass ratio of the epoxy resins containing dynamic disulfide bonds represented by Structural Formula I, Structural Formula II, and Structural Formula III is 100:10:15.

[0109] Furthermore, the commercial epoxy resin includes bisphenol A epoxy resin (E51) and brominated epoxy resin, wherein the mass ratio of bisphenol A epoxy resin (E51) to brominated epoxy resin is 100:7.5, and the mass ratio of commercial epoxy resin to dynamic disulfide bond epoxy resin is 12.5:100.

[0110] Furthermore, the carboxylic acid curing agent containing a dynamic disulfide bond includes substances represented by structural formula IV to structural formula VI:

[0111]

[0112]

[0113] The value of n is 4.

[0114] Furthermore, the mass ratio of the carboxylic acid curing agents containing dynamic disulfide bonds represented by structural formula IV, structural formula V, and structural formula VI is 100:20:7.5.

[0115] Furthermore, the functional rubber toughening agent is a nitrile rubber containing epoxy groups, and the amount used is 2% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0116] Furthermore, the functionalized graphene oxide nanosheets are amino-functionalized graphene oxide nanosheets, and the amount used is 0.75% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin.

[0117] Furthermore, the thermoplastic resin toughening agent is a micro-powdered thermoplastic polyester having two particle sizes, one with a particle size range of 20 to 50 μm and the other with a particle size range of 80 to 170 μm, and the weight ratio of the two particle sizes of thermoplastic polyester is 17.5:100.

[0118] Furthermore, the melting range of the micro-powdered thermoplastic polyester is 115°C to 140°C.

[0119] Furthermore, the mass ratio of the micro-powdered thermoplastic polyester to the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin is 55:100.

[0120] Furthermore, the molar ratio of epoxy groups to carboxyl groups in the self-healing epoxy structural adhesive formula is 1.08:1.

[0121] Furthermore, the transesterification agent is a mixture of zinc acetylacetonate and dibutyltin oxide.

[0122] Furthermore, the amount of the transesterification agent used is 2.75% of the molar amount of epoxy groups in the self-repairing epoxy structural adhesive formula.

[0123] Furthermore, the synthesis of the epoxy resin containing dynamic disulfide bonds comprises the following steps:

[0124] Epichlorohydrin, deionized water, and ethylene glycol were added to a four-necked flask equipped with a stirrer, condenser, dropping funnel, and nitrogen atmosphere. Heat in an oil bath at 50°C. Bis(4-hydroxyphenyl) disulfide was added in four portions. After the addition, the temperature of the reaction system was maintained at 60°C for 1.5 hours. Chloroform was then added and the reaction was continued with stirring for 6 hours. The temperature was then lowered to 40°C, and a 40% aqueous solution of NaOH was slowly and uniformly added dropwise. The temperature was maintained at this temperature for 115 minutes. After the reaction is completed, the reaction mixture is cooled to room temperature and chloroform is added to a four-necked flask. The reaction solution is transferred to a separatory funnel and washed with deionized water 4 times. After standing for stratification, the lower layer solution is taken into a beaker, anhydrous MgSO4 is added, and stirred for 2 hours. MgSO4 is removed by filtration, and the solvent is distilled off. The product is separated and purified by silica gel column chromatography, using dichloromethane as the eluent. After the eluent is distilled off, the product is vacuum-dried for 18 hours to obtain an epoxy resin containing a dynamic disulfide bond, as shown in structural formula I. Bis(2-hydroxyethyl) disulfide is replaced by bis(4-hydroxyphenyl) disulfide, and the above preparation steps are repeated to obtain an epoxy resin containing a dynamic disulfide bond as shown in structural formula II. 1,1'-disulfadiylbis( The above preparation steps are repeated to prepare an epoxy resin containing dynamic disulfide bonds as shown in structural formula III, wherein the molar ratio of bis(4-hydroxyphenyl) disulfide, bis(2-hydroxyethyl) disulfide and 1,1'-dithiodiylbis(2,2,6,6-tetramethylpiperidin-4-ol) to epichlorohydrin is 1:1; epichlorohydrin, deionized water and ethylene glycol are mixed in any proportion; the ratio of epichlorohydrin to aqueous NaOH solution is 1 mol:175 ml; the ratio of bithoxydichloroform to epichlorohydrin is 3.5 ml:1 ml; and the ratio of epichlorohydrin to MgSO4 is 1 ml:3.5 g.

[0125] Furthermore, the synthesis method of the carboxylic acid curing agent IV containing a dynamic disulfide bond comprises the following steps:

[0126] Under nitrogen protection, 4,4'-diaminodiphenyl disulfide was dissolved in chloroform in a three-necked flask, wherein the mass volume ratio of 4,4'-diaminodiphenyl disulfide to chloroform was 1 g / 15 ml, and the mixture was stirred at 50°C for 45 min. Acrylic acid was added dropwise, wherein the molar ratio of 4,4'-diaminodiphenyl disulfide to acrylic acid was 1:2. After the addition of acrylic acid, the mixture was stirred in the dark at 50°C for 22 h. After distilling off the solvent, the product was separated and purified by silica gel column chromatography using chloroform as the eluent. After distilling off the eluent, a dynamic disulfide bond-containing carboxylic acid curing agent IV was obtained.

[0127] Furthermore, the self-repairing epoxy structural adhesive is prepared by a physical mixing method of hot melt blending, grinding dispersion, and vacuum kneading, and the specific steps are as follows:

[0128] (1) Preparation of hot melt blends

[0129] 12.5% ​​by weight of a thermoplastic polyester with a particle size range of 20 to 50 μm and 7.5% by weight of a thermoplastic polyester with a particle size range of 80 to 170 μm were uniformly mixed with a bisphenol A epoxy resin (E51). The mixture was melted and stirred in a hot-melt reactor heated by circulating oil until the thermoplastic resin was completely melted in the bisphenol A epoxy resin (E51), forming a uniform and transparent hot-melt blend A. The temperature of the blend was maintained at 170°C.

[0130] (2) Preparation of rubber-toughened epoxy resin

[0131] The dynamic disulfide bond-containing epoxy resin and the functionalized rubber toughening agent were added to a single-necked flask containing ethyl acetate, stirred at room temperature until they were completely dissolved to form a uniform system, and the ethyl acetate was removed by rotary distillation to obtain the rubber toughened epoxy resin B.

[0132] (3) Preparation of grinding dispersion resin

[0133] A rubber-toughened epoxy resin B, a carboxylic acid curing agent IV containing dynamic disulfide bonds, amino-functionalized graphene oxide nanosheets, and an ester exchange agent were mixed to form a crude mixture C. The crude mixture C was then ground and dispersed four times on a ceramic three-roll mill to obtain a ground and dispersed resin D. The roller surface temperature of the three-roll mill was controlled at 42.5°C.

[0134] (4) The hot melt blend A is preheated in a blast drying oven at 75°C for 150 minutes, and the vacuum kneader is set to 60°C for 150 minutes. The preheated hot melt blend A, rubber toughened epoxy resin B, ground dispersed resin D, remaining thermoplastic polyester, carboxylic acid curing agents V and VI containing dynamic disulfide bonds, and brominated epoxy resin are added to the preheated vacuum kneader and vacuum kneaded for 20 minutes to obtain a self-healing epoxy structural adhesive. The material temperature is controlled at 65°C and the vacuum degree is controlled at -0.097 MPa.

[0135] The resulting self-healing epoxy structural adhesive was used to bond aluminum alloy single lap shear test pieces with a 0.2mm adhesive layer thickness. The pieces were cured in a 160°C oven for 3.5 hours. After cooling to room temperature, the bonded pieces were removed for tensile shear testing and the shear strength was calculated. The two test pieces were then bonded face-to-face with the adhesive-attached side. A pressure of 0.3 MPa was applied and the pieces were repaired in a 160°C oven for 4.5 hours. After cooling to room temperature, the bonded pieces were removed for tensile shear testing and the shear strength of the repaired pieces was calculated.

[0136] The self-repairing epoxy structural adhesive prepared by the above steps contains double dynamic covalent bonds, and the exchange of double dynamic covalent bonds occurs during the repair process. The self-repairing epoxy structural adhesive has the advantages of high bonding performance and multiple efficient self-repair. Its shear strength is 29.0 MPa, the shear strength repair efficiency is 91%, and the shear strength after repair is 26.4 MPa.

Claims

1. An epoxy resin containing dynamic covalent bonds, characterized in that: The epoxy resin containing dynamic covalent bonds is an epoxy resin containing dynamic disulfide bonds, and the epoxy resin molecules containing dynamic disulfide bonds include epoxy resins shown in structural formula I, structural formula II or structural formula III.

2. A method for preparing an epoxy resin containing dynamic covalent bonds according to claim 1, characterized in that: The method comprises the following steps: adding epichlorohydrin, deionized water and ethylene glycol into a four-necked flask equipped with a stirrer, a condensing device, a dropping funnel and nitrogen protection, heating in an oil bath at 40-60° C., adding bis(4-hydroxyphenyl) disulfide in 3-5 times, controlling the temperature of the reaction system at 50-70° C. after reaction for 1-2 hours, adding chloroform, continuing to stir and react for 4-8 hours, lowering the temperature to 30-50° C., and slowly and uniformly dropping a 30%-50% NaOH aqueous solution. , keep warm for 60 to 150 minutes, after the reaction is completed, cool the reaction mixture to room temperature, add chloroform to a four-necked flask, transfer the reaction solution to a separatory funnel, and wash with deionized water several times; after standing and stratifying, take the lower layer solution to a beaker, add anhydrous MgSO4, and stir for 1 to 3 hours; filter to remove MgSO4, distill off the solvent, separate and purify the product by silica gel column chromatography, use dichloromethane as the eluent, distill off the eluent, and vacuum dry to obtain a product containing dynamic disulfide bonds The epoxy resin is shown in the structural formula I; bis(4-hydroxyphenyl) disulfide is replaced by bis(2-hydroxyethyl) disulfide, and the above preparation is repeated to obtain an epoxy resin containing dynamic disulfide bonds as shown in the structural formula II; bis(4-hydroxyphenyl) disulfide is replaced by 1,1'-disulfadiylbis(2,2,6,6-tetramethylpiperidin-4-ol), and the above preparation is repeated to obtain an epoxy resin containing dynamic disulfide bonds as shown in the structural formula III, wherein bis(4-hydroxyphenyl) disulfide, bis(2 The molar ratio of epichlorohydrin to 1,1'-dithiodiylbis(2,2,6,6-tetramethylpiperidin-4-ol) is 1:1; epichlorohydrin, deionized water and ethylene glycol are mixed in any proportion; the ratio of epichlorohydrin to NaOH aqueous solution is 1 mol:150-200 ml; the ratio of chloroform added twice to epichlorohydrin is 2 ml-5 ml:1 ml; the ratio of epichlorohydrin to MgSO4 is 1 ml:2 g-5 g.

3. A method for preparing a self-repairing epoxy structural adhesive, characterized in that: The components of the self-healing epoxy structural adhesive include an epoxy resin containing dynamic disulfide bonds, a commercial epoxy resin, a carboxylic acid curing agent containing dynamic disulfide bonds, a functionalized rubber toughening agent, a functionalized graphene oxide nanosheet, a thermoplastic resin toughening agent and an ester exchange agent. The self-healing epoxy structural adhesive is prepared by mixing through the physical steps of hot melt blending, grinding and dispersing, and vacuum kneading; the epoxy resin containing dynamic disulfide bonds includes the epoxy resins shown in structural formula I, structural formula II and structural formula III described in claim 1.

4. The preparation method according to claim 3, characterized in that: The mass ratio of the epoxy resin containing dynamic disulfide bonds shown in structural formula I, structural formula II and structural formula III is 100:5-15:10-20.

5. The preparation method according to claim 3, characterized in that: The carboxylic acid curing agent containing dynamic disulfide bonds includes substances represented by structural formula IV to structural formula VI: The value of n is 3 to 5; The mass ratio of the carboxylic acid curing agent containing dynamic disulfide bonds shown in structural formula IV, structural formula V and structural formula VI is 100:10-30:5-10; the molar ratio of epoxy group to carboxyl group in the formula of the self-repairing epoxy structural adhesive is 1.06-1.10:

1.

6. The preparation method according to claim 5, characterized in that: The thermoplastic resin toughening agent is a micro-powdered thermoplastic polyester, which has two particle sizes, one with a particle size range of 20 to 50 μm and the other with a particle size range of 80 to 170 μm. The mass ratio of the two particle sizes of the thermoplastic polyester is 10 to 25:

100. The melting range of the micro-powdered thermoplastic polyester is 115° C. to 140° C. The mass ratio of the micro-powdered thermoplastic polyester to the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin is 40 to 65:

100.

7. The preparation method according to claim 6, characterized in that: The commercial epoxy resin comprises bisphenol A epoxy resin and brominated epoxy resin, the mass ratio of bisphenol A epoxy resin to brominated epoxy resin is 100:5-10, and the mass ratio of commercial epoxy resin to epoxy resin containing dynamic disulfide bonds is 5-20:

100.

8. The preparation method according to claim 3, characterized in that: The functionalized rubber toughening agent is nitrile rubber containing epoxy groups, and the amount used is 1%-3% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin; the functionalized graphene oxide nanosheets are amino-functionalized graphene oxide nanosheets, and the amount used is 0.5%-1.0% of the total mass of the epoxy resin containing dynamic disulfide bonds and the commercial epoxy resin; the transesterification agent is a mixture of one or more of triphenylphosphine, zinc acetylacetonate, dibutyltin oxide, tributyltin chloride titanium isopropoxide, butyl titanate, and dichlorobis(pentyl)tantalum, and the amount used of the transesterification agent is 0.5%-5% of the molar amount of epoxy groups in the epoxy structural adhesive formula.

9. The preparation method according to claim 7, characterized in that: The self-repairing epoxy structural adhesive is prepared by a physical mixing method of hot melt blending, grinding dispersion, and vacuum kneading, and the specific steps are as follows: (1) Preparation of hot melt blends 10% to 15% of the total mass of thermoplastic polyester with a particle size range of 20 to 50 μm and 5% to 10% of the total mass of thermoplastic polyester with a particle size range of 80 to 170 μm are uniformly mixed with bisphenol A type epoxy resin, and melted and stirred in a hot melt reactor heated by circulating oil until the thermoplastic polyester is completely melted in the bisphenol A type epoxy resin to form a uniform and transparent hot melt blend A, wherein the temperature of the blend is maintained at 150 to 180° C.; (2) Preparation of rubber toughened epoxy resin Three epoxy resins containing dynamic disulfide bonds and a functional rubber toughening agent were added into a single-necked flask containing ethyl acetate, stirred at room temperature until they were completely dissolved to form a uniform system, and the ethyl acetate was removed by rotary distillation to obtain a rubber toughened epoxy resin B; (3) Preparation of grinding dispersion resin A rubber toughened epoxy resin B, a carboxylic acid curing agent IV containing a dynamic disulfide bond, a functionalized graphene oxide nanosheet, and an ester exchange agent are mixed to form a crude mixture C, and the crude mixture C is ground and dispersed on a ceramic three-roll mill for several times to obtain a ground and dispersed resin D; wherein the roller surface temperature of the three-roll mill is controlled within a range of 25 to 60° C.; (4) The hot melt blend A is preheated in a forced air drying oven at a temperature of 60 to 90° C., and the heating temperature of the vacuum kneader is set at 50 to 70° C. for 120 to 180 min. The preheated hot melt blend A, rubber toughened epoxy resin B, ground dispersed resin D, remaining thermoplastic polyester, carboxylic acid curing agents V and VI containing dynamic disulfide bonds, and brominated epoxy resin are added to the preheated vacuum kneader, and vacuum kneading is performed to obtain a self-healing epoxy structural adhesive, wherein the material temperature is controlled at 50 to 80° C., and the vacuum degree is controlled at -0.098 MPa to -0.095 MPa.

10. The preparation method according to claim 5, characterized in that: The synthesis method of the dynamic bond carboxylic acid curing agent IV comprises the following steps: under nitrogen protection, dissolving 4,4'-diaminodiphenyl disulfide in chloroform in a three-necked flask, wherein the mass volume ratio of 4,4'-diaminodiphenyl disulfide to chloroform is 1g / 10-20ml, stirring at 40-60°C for 30-60min, and adding acrylic acid dropwise, wherein the molar ratio of 4,4'-diaminodiphenyl disulfide to acrylic acid is 1:2, stirring at 40-60°C in the dark for 15-30h after adding acrylic acid, and separating and purifying the product after distilling off the solvent by silica gel column chromatography, using chloroform as eluent, and distilling off the eluent to obtain a carboxylic acid curing agent IV containing a dynamic disulfide bond.

Images