Preparation method and application of self-repairing toughened epoxy-modified cyanate ester resin

Abstract

The application belongs to the technical field of high-performance functional polymer materials, and discloses a preparation method of self-repairing and toughening type epoxy modified cyanate ester resin; a 4,4'-diaminodiphenyl disulfide end-capped polyurethane oligomer curing agent containing a disulfide bond is used as a disulfide bond type curing agent; a pyridine type latent curing agent is prepared by reacting a metal salt, a pyridine amine compound and an isocyanate end-capped polyurethane oligomer; and the disulfide bond type curing agent, the pyridine type latent curing agent and a matrix resin are subjected to pre-coordination reaction and then cured to obtain the epoxy modified cyanate ester resin. The application also discloses application of the epoxy modified cyanate ester resin obtained by the above preparation method in the field of automobile lightweight structural parts or radar wave-transparent structural parts. The application uses the disulfide bond type curing agent and the pyridine type latent curing agent, and a multi-layer energy dissipation structure is formed by dynamic disulfide bonds in a crosslinking network and pyridine amine-metal ligands, so that the toughness and self-repairing capability of the epoxy modified cyanate ester resin can be synergistically improved.

Description

Technical Field

[0001] This invention belongs to the field of high-performance functional polymer materials technology, and specifically relates to a method for preparing and applying a self-healing and toughened epoxy-modified cyanate ester resin. Background Technology

[0002] After high-temperature curing, cyanate ester resins form a rigid triazine ring cross-linked network, which has the problem of intrinsic brittleness. At the same time, surface scratches are prone to occur during use, affecting the long-term service life.

[0003] To address the inherent brittleness and surface scratch susceptibility of cyanate ester resins, thermosetting resins such as bismaleimide resins and epoxy resins are commonly used for modification. This modification can improve the inherent brittleness of the resin while retaining its excellent properties. For example, Chinese Patent CN107686658A discloses a method for preparing bismaleimide resin-toughened cyanate ester resin prepreg. The method involves feeding bismaleimide resin and cyanate ester resin at a mass ratio of 4:6, coating to form a resin film, and then hot-pressing and impregnating with fibers to obtain a bismaleimide-modified cyanate ester resin prepreg. Because the overall crosslinking density of the system decreases after curing, toughness is effectively improved. However, the crosslinking network structure remains rigid, limiting the toughening effect and making it difficult to meet practical application requirements.

[0004] Unlike bismaleimide resins, epoxy resins contain ether bonds, resulting in higher flexibility, which is more conducive to improving the toughness of cyanate ester resins. However, the curing mechanisms of cyanate ester resins and epoxy resins differ significantly, making it difficult for traditional curing agents to cure effectively. Recently developed curing agent design strategies based on dynamic covalent chemistry are not only applicable to the curing of epoxy resins and epoxy-modified cyanate ester resins, but also utilize the reversible breaking and recombination characteristics of dynamic covalent bonds to achieve synergistic improvement in resin processing and performance, providing a new approach to solving the aforementioned problems. For example, Chinese patent CN116285567B discloses a method for preparing toughened epoxy powder coatings. A 3-[4-(aminomethyl)-1,2-dioxoborane-2-yl]aniline-terminated polyurethane prepolymer is used as a curing agent to cure epoxy resin, introducing dynamic borate ester bonds and hydrogen bonds into the polymer network. When scratches appear on the coating surface, heating in a 100°C oven for 2 hours completely eliminates the scratches, indicating that the dynamic borate ester bonds have a self-healing effect. Furthermore, when subjected to external forces, hydrogen bonds dissipate energy through breakage and recombination, improving toughness to some extent. However, borate ester bonds are extremely sensitive to water and are prone to hydrolysis in humid environments, resulting in poor coating stability. On the other hand, hydrogen bonds have low bond energy and limited energy dissipation, making it difficult to effectively address the intrinsic brittleness of resins.

[0005] Therefore, how to utilize a curing agent design strategy based on dynamic covalent chemistry to provide a method for preparing epoxy-modified cyanate ester resins that synergistically enhances toughness and self-healing properties is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a self-healing and toughened epoxy-modified cyanate resin. By using a curing agent design strategy based on dynamic covalent chemistry, disulfide bond-based curing agents and pyridine-based latent curing agents suitable for epoxy-modified cyanate resin are prepared. Because the dynamic disulfide bonds and pyridine amine-metal ligands in the crosslinking network form a multilayer energy dissipation structure, the toughness and self-healing ability of the epoxy-modified cyanate resin can be synergistically improved.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a self-healing and toughened epoxy-modified cyanate ester resin, the method comprising:

[0009] 1) Prepare a polyurethane oligomer curing agent with 4,4'-diaminodiphenyl disulfide end capping containing disulfide bonds as a disulfide bond curing agent.

[0010] 2) Prepare pyridine-based latent curing agents by reacting 2,2-dihydroxymethylbutyric acid, pyridine amine compounds, metal salts and isocyanate-terminated polyurethane oligomers;

[0011] 3) A matrix resin precursor solution is obtained by pre-coordination reaction of disulfide bond curing agent, pyridine latent curing agent and matrix resin. The matrix resin includes epoxy resin and cyanate ester resin. The self-healing toughened epoxy modified cyanate ester resin is obtained by staged curing.

[0012] This invention provides a self-healing and toughened epoxy-modified cyanate ester resin based on a dynamic disulfide bond and pyridine amine-metal ligand structure. The disulfide bond curing agent contains dynamic disulfide bonds, which can undergo reversible breakage and recombination under external stimuli, endowing the polymer network with self-healing capabilities. The pyridine-based latent curing agent has low viscosity, facilitating liquid molding processes. Furthermore, the introduction of a metal salt can form a pyridine amine-metal ligand with pyridine amine compounds, blocking the activity of pyridine urea bonds at low temperatures, giving the resin precursor an ultra-long operating period; while at high temperatures, the pyridine amine-metal ligand dissociates, allowing the resin to cure rapidly. More importantly, the metal ligand can induce microphase separation in the polyurethane segments, effectively improving the intrinsic brittleness of the cyanate ester resin network, and forming a multilayer energy dissipation structure with the dynamic disulfide bonds, thereby achieving a synergistic improvement in toughness and self-healing capabilities.

[0013] The raw materials for preparing the polyurethane oligomer include diisocyanate, polyol, and catalyst. The number average molecular weight of the polyurethane oligomer is 1,000 to 20,000 g / mol. The diisocyanate is selected from at least one of aliphatic, alicyclic, or aromatic diisocyanates. The polyol is selected from at least one of polyester glycol, polyether glycol, or polycarbonate glycol with a number average molecular weight of 500 to 5,000 g / mol. The amount of catalyst added is 1% to 3% of the total mass of diisocyanate and polyol. The molar ratio of diisocyanate to polyol is (1.8 to 2.2): (0.9 to 1.1).

[0014] Preferably, the synthesis of the polyurethane oligomer is carried out under inert gas conditions, wherein the inert gas is one of nitrogen, argon, or helium.

[0015] Preferably, the diisocyanate is selected from isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, or toluene diisocyanate. Considering the viscosity and flowability of the oligomer, isophorone diisocyanate is more suitable; the polyol is selected from polycaprolactone diol, polytetrahydrofuran diol, or polypropylene glycol. More preferably, considering that a number-average molecular weight of 500 to 5000 g / mol is more beneficial to the flexibility of the polyurethane oligomer, polycaprolactone diol is more suitable.

[0016] The raw materials for preparing the disulfide bond-based curing agent include 4,4'-diaminodiphenyl disulfide containing disulfide bonds and a polyurethane oligomer. The molar ratio of the 4,4'-diaminodiphenyl disulfide to the diisocyanate used to synthesize the polyurethane oligomer is 1:(1.8~2.2). The structural formula of the disulfide bond-based curing agent is as follows:

[0017] ;

[0018] In the formula: n is a positive integer greater than or equal to 1.

[0019] The disulfide bond-based curing agent provided by this invention contains a flexible long polyurethane chain in the middle, with benzene rings and dynamic disulfide bonds at both ends. By using a modified curing agent containing dynamic disulfide covalent bonds to replace the traditional curing agent with irreversible permanent crosslinking, when epoxy resin is scratched, the dynamic disulfide bonds at the scratch site can be reversibly broken and recombined under the action of external stimuli such as heat and light, realizing in-situ self-repair of scratches and effectively improving the problem of difficult repair of scratches on composite materials.

[0020] Preferably, the pyridine amine compound is selected from at least one of 2-aminopyridine, 2,3-aminopyridine, 4-aminopyridine, 3-aminopyridine-2-carboxamide, or 2-mercapto-3-aminopyridine; the molar ratio of the pyridine amine compound, 2,2-dimethylolbutyric acid, and the diisocyanate used to synthesize the polyurethane oligomer is (0.5~1):(0.5~0.7):(1.8~2.2). The structural formula of the pyridine amine compound is:

[0021] .

[0022] Preferably, the metal salt is selected from at least one of copper, zinc, nickel, or iron salts; wherein the copper salt is one of copper chloride, copper nitrate, copper bromide, copper sulfate, copper acetate, or copper trifluoromethanesulfonate. The molar ratio of the metal ion to the nitrogen atom on the pyridine ring in the pyridine-based latent curing agent is 1:(1~3).

[0023] Taking copper ions as an example, the structural formula of pyridine-based latent curing agents is as follows:

[0024] ;

[0025] In the formula: n is a positive integer greater than or equal to 1.

[0026] In the pyridine-based latent curing agent provided by this invention, the hydrogen atom on the amino group of the pyridine amine compound reacts with the isocyanate group to form a pyridine urea bond; the nitrogen atom on the pyridine ring can coordinate with the metal ion in the metal salt to form a pyridine amine-metal ligand structure. Furthermore, the pyridine-based curing agent has low viscosity, which is beneficial for liquid molding processes. In addition, the introduction of the metal salt can form a pyridine amine-metal ligand with the pyridine amine compound, blocking the activity of the pyridine urea bond at low temperatures, giving the resin precursor liquid an ultra-long operating period; while at high temperatures, the pyridine amine-metal ligand dissociates, allowing the resin to cure rapidly. More importantly, the metal ligand can induce microphase separation of polyurethane segments and form a multilayer energy dissipation structure with dynamic disulfide bonds, thereby achieving a synergistic improvement in toughness and self-healing ability.

[0027] Preferably, the epoxy resin is at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, or alicyclic epoxy resin; the cyanate ester resin is selected from at least one of bisphenol A type cyanate ester, bisphenol E type cyanate ester, bisphenol M type cyanate ester, tetramethylbisphenol F type cyanate ester, phenolic type cyanate ester, and dicyclopentadiene type cyanate ester; the molar ratio of the epoxy group in the epoxy resin to the active hydrogen on the amino group on the benzene ring in the disulfide bond curing agent is 1:(0.5~1.5); the molar ratio of the epoxy group in the epoxy resin to the active hydrogen on the amino group on the pyridine ring in the pyridine latent curing agent is 1:(0.5~1.5); and the molar ratio of the cyanate group in the cyanate ester resin to the epoxy group in the epoxy resin is 1:(1~1.5).

[0028] Preferably, the preparation method of the self-healing and toughening epoxy-modified cyanate ester resin includes:

[0029] 1) Diisocyanate, polyol and catalyst dibutyltin dilaurate are blended and reacted under mechanical stirring at 40°C~70°C for 2~6 h to obtain isocyanate-terminated polyurethane prepolymer;

[0030] 2) Dissolve 4,4'-diaminodiphenyl disulfide in anhydrous N,N-dimethylformamide, add it to isocyanate-terminated polyurethane prepolymer, and continue the reaction at 40°C~60°C for 10~15 h to obtain disulfide bond curing agent SS;

[0031] 3) Dissolve 2,2-dimethylolbutyric acid and pyridine amine compounds in anhydrous N,N-dimethylformamide, add them to isocyanate-terminated polyurethane prepolymer, and continue the reaction at 40°C~60°C for 10~15 h to obtain pyridine amine-terminated linear prepolymer; blend the pyridine amine-terminated linear prepolymer with a metal salt and mix at 50°C~70°C for 10~30 min to obtain a pyridine-based latent curing agent;

[0032] 4) The disulfide bond curing agent, pyridine amine latent curing agent, epoxy resin and cyanate ester resin are subjected to a pre-coordination reaction at 40~100°C for 10~40 min; the matrix resin is added and mixed at 40~100°C for 20~40 min to obtain the matrix resin precursor solution.

[0033] 5) The matrix resin precursor liquid is cured in stages: first, it is pre-cured at 70~90°C for 1~3 h, then cured at 110~130°C for 1~3 h, and finally post-cured at 140~160°C for 4~8 h to obtain self-healing toughened epoxy modified cyanate resin.

[0034] The reaction in step 1) above is illustrated by the following reaction formula:

[0035] ;

[0036] In the formula: n is a positive integer greater than or equal to 1;

[0037] The reaction in step 2) above is illustrated with the following reaction formula:

[0038] ;

[0039] In the formula: n is a positive integer greater than or equal to 1;

[0040] The reaction in step 3) above is illustrated with the following reaction formula:

[0041] ;

[0042] In the formula: n is a positive integer greater than or equal to 1.

[0043] This invention also provides the application of the self-healing and toughened epoxy-modified cyanate ester resin obtained by the above preparation method in the fields of lightweight automotive structural components or radar transparent structural components.

[0044] The self-healing and toughened epoxy-modified cyanate ester resin is used as the matrix resin to impregnate carbon fiber fabric and then cured to prepare carbon fiber composite material, which is used as a lightweight structural component for automobiles or a radar-transparent structural component.

[0045] This invention employs a vacuum-assisted resin infusion process to prepare carbon fiber composite materials. Specifically, first, a structural mold is selected, then carbon fiber fabric is laid in the mold and a vacuum is applied; subsequently, a self-healing, type-modifying epoxy cyanate ester resin obtained by the above preparation method is used as the matrix resin, and the carbon fiber fabric is impregnated under vacuum negative pressure conditions. The composite material is then cured in stages to produce a carbon fiber composite material, such as for automotive hoods and radar domes.

[0046] Compared with the prior art, the present invention has the following beneficial effects and outstanding advantages:

[0047] (1) The raw materials used in this invention are all conventional chemicals with stable sources, which are convenient for industrial preparation and promotion and application, while ensuring the flexibility of the molecular structure design of the curing agent.

[0048] (2) The polyurethane oligomers prepared in this invention are obtained by reacting diisocyanate and polyol under the catalysis of a catalyst (such as dibutyltin dilaurate). The synthesis process is well-defined. Because there are many types of polyols, their number-average molecular weights can be selected from 500 to 5000 g / mol, so that the number-average molecular weight of the polyurethane oligomers can be dynamically controlled from 1000 to 20000 g / mol, further optimizing the flowability, flexibility and mechanical properties of the curing agent after curing.

[0049] (3) The disulfide bond curing agent prepared in this invention contains dynamic disulfide bonds, which can undergo reversible breakage and recombination under external stimulation (heating or ultraviolet light), giving the polymer network self-healing ability without any catalyst. In daily life, the cracked area can be irradiated with ultraviolet light for 0.5 to 5 hours to achieve in-situ self-repair of scratches.

[0050] (4) The pyridine latent curing agent prepared by the present invention has low viscosity, which is beneficial to liquid molding process and improves resin wettability and layer uniformity.

[0051] (5) The pyridine latent curing agent prepared in this invention contains a metal salt. The presence of the metal salt can form a pyridine amine-metal ligand with pyridine amine compounds, which can block the activity of pyridine urea bonds at low temperatures, giving the resin precursor liquid an ultra-long operating period. At high temperatures, the metal ligand dissociates, allowing the epoxy modified cyanate resin to cure rapidly.

[0052] (6) In the epoxy-modified cyanate ester resin system prepared by this invention, the polyol is a flexible segment, while the aromatic benzene ring, pyridine urea bond, and urethane bond are hard segments, providing the preconditions for microphase separation of the system. On the other hand, the introduction of metal salts can form pyridine amine-metal ligands with pyridine amine compounds, further inducing microphase separation of the polyurethane soft segments, and forming a multilayer energy dissipation structure with dynamic disulfide bonds. Under external stress, this multilayer structure can effectively disperse stress, hinder crack propagation, and at the same time endow the material with significant self-healing ability, thereby achieving a synergistic improvement in toughness and self-healing performance.

[0053] (7) In the epoxy-modified cyanate ester resin system prepared by this invention, the dynamic disulfide bonds and pyridineamine-metal ligands exhibit chemical stability and do not easily break under normal temperature and without external stimuli, thus ensuring the stability of the resin. When the epoxy-modified cyanate ester resin containing disulfide bonds and pyridineamine-metal ligands is immersed in hydrochloric acid aqueous solution or ethyl acetate organic solvent for one month, no significant dissolution or structural damage occurs; only slight surface swelling is observed, demonstrating that the network can maintain its integrity in acidic or organic solvent environments. Attached Figure Description

[0054] Figure 1 The spectrum of the ultraviolet lamp used in the self-healing capability test during the performance comparison test of this invention (power: 31.3 mW / cm²). 2 (Wavelength: 300-600 nm). Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to multiple embodiments and experimental data. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit its scope.

[0056] Example 1: Synthesis of disulfide bond-based curing agent SS

[0057] Table 1. Raw materials used in the synthesis of disulfide bond-based curing agent SS in Example 1

[0058]

[0059] Preparation method:

[0060] Step 1: Polycaprolactone diol was dried in a 120°C oven for 2 hours to remove moisture. Then, under inert gas protection, 0.018 mol of isophorone diisocyanate, 0.009 mol of polycaprolactone diol, and 1% of the total mass of dibutyltin dilaurate catalyst were added sequentially to a 100 ml three-necked flask. The mixture was mechanically stirred at 50°C for 4 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0061] Step 2: Dissolve 0.01 mol of 4,4'-diaminodiphenyl disulfide in 10 ml of anhydrous N,N-dimethylformamide and transfer to a dropping funnel. Slowly add the solution dropwise to the isocyanate-terminated polyurethane prepolymer over 15 min. After the addition is complete, continue the reaction at 50°C for 13 h to obtain the disulfide bond curing agent SS.

[0062] Example 2: Synthesis of latent curing agent AMPU-CuCl2

[0063] Table 2. Raw materials used in the synthesis of the latent curing agent AMPU-CuCl2 in Example 2

[0064]

[0065] Preparation method:

[0066] Step 1: Polycaprolactone diol was dried in a 120°C oven for 2 hours to remove moisture. Then, under inert gas protection, 0.018 mol of isophorone diisocyanate, 0.009 mol of polycaprolactone diol, and 1% of the total mass of dibutyltin dilaurate catalyst were added sequentially to a 100 ml three-necked flask. The mixture was mechanically stirred at 50°C for 4 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0067] Step 2: Dissolve 0.006 mol of 2,2-dimethylolbutyric acid and 0.007 mol of 2,3-aminopyridine in 10 mL of anhydrous N,N-dimethylformamide and transfer to a dropping funnel. Slowly add the solution dropwise to the isocyanate-terminated polyurethane prepolymer over 15 min. After the addition is complete, continue the reaction at 50°C for 13 h to obtain a pyridineamine-terminated linear prepolymer.

[0068] Step 3: Weigh 1 mol of the prepared linear prepolymer and 1 mol of copper chloride, place them in a glass sample bottle, and mix them magnetically at 60°C for 15 min to obtain the target latent curing agent AMPU-CuCl2.

[0069] Example 3: Synthesis of the latent curing agent AMPU-CuBr2

[0070] Table 3. Raw materials used in the synthesis of the latent curing agent AMPU-CuBr2 in Example 3

[0071]

[0072] Preparation method:

[0073] Step 1: Polycaprolactone diol was dried in a 120°C oven for 2 hours to remove moisture. Then, under inert gas protection, 0.018 mol of isophorone diisocyanate, 0.009 mol of polycaprolactone diol, and 1% of the total mass of dibutyltin dilaurate catalyst were added sequentially to a 100 ml three-necked flask. The mixture was mechanically stirred at 50°C for 4 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0074] Step 2: Dissolve 0.006 mol of 2,2-dimethylolbutyric acid and 0.007 mol of 2,3-aminopyridine in 10 mL of anhydrous N,N-dimethylformamide and transfer to a dropping funnel. Slowly add the solution dropwise to the isocyanate-terminated polyurethane prepolymer over 15 min. After the addition is complete, continue the reaction at 50°C for 13 h to obtain a pyridineamine-terminated linear prepolymer.

[0075] Step 3: Weigh 1 mol of the prepared linear prepolymer and 1 mol of copper bromide, place them in a glass sample bottle, and mix them magnetically at 60°C for 15 min to obtain the target latent curing agent AMPU-CuBr2.

[0076] Example 4: Synthesis of latent curing agent AMPU-Cu(NO3)2

[0077] Table 4. Raw materials used in the synthesis of the latent curing agent AMPU-Cu(NO3)2 in Example 4

[0078]

[0079] Preparation method:

[0080] Step 1: Polycaprolactone diol was dried in a 120°C oven for 2 hours to remove moisture. Then, under inert gas protection, 0.018 mol of isophorone diisocyanate, 0.009 mol of polycaprolactone diol, and 1% of the total mass of dibutyltin dilaurate catalyst were added sequentially to a 100 ml three-necked flask. The mixture was mechanically stirred at 50°C for 4 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0081] Step 2: Dissolve 0.006 mol of 2,2-dimethylolbutyric acid and 0.007 mol of 2,3-aminopyridine in 10 mL of anhydrous N,N-dimethylformamide and transfer to a dropping funnel. Slowly add the solution dropwise to the isocyanate-terminated polyurethane prepolymer over 15 min. After the addition is complete, continue the reaction at 50°C for 13 h to obtain a pyridineamine-terminated linear prepolymer.

[0082] Step 3: Weigh 1 mol of the prepared linear prepolymer and 1 mol of copper nitrate, place them in a glass sample bottle, and mix them magnetically at 60°C for 15 min to obtain the target latent curing agent AMPU-Cu(NO3)2.

[0083] Example 5: Preparation of epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2

[0084] Table 5. Raw materials used in the synthesis of epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2 in Example 5

[0085]

[0086] Preparation method:

[0087] Step 1: Weigh 1 mol of the disulfide bond curing agent SS prepared in Example 1, 1 mol of the latent curing agent AMPU-CuCl2 prepared in Example 2, add 2 mol of bisphenol A epoxy resin and 2 mol of bisphenol A cyanate, and magnetically stir the pre-ligand reaction at 60°C for 30 min until a uniform matrix resin precursor solution is obtained.

[0088] Step 2: After removing air bubbles by ultrasonication, the matrix resin precursor liquid is poured into an aluminum mold;

[0089] Step 3: Perform segmented curing according to the following procedure: pre-curing at 80°C for 2 h, then heating the system to 120°C for 2 h, and finally curing at 150°C for 6 h to obtain the epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2. Performance tests were performed on the cured product, and the results are shown in the table below.

[0090] Example 6: Preparation of epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuBr2

[0091] Table 6. Raw materials used in the synthesis of epoxy-modified cyanate ester resin EP-SS-AMPU-CuBr2 in Example 6

[0092]

[0093] Preparation method:

[0094] Step 1: Weigh 1 mol of the disulfide bond curing agent SS prepared in Example 1, 1 mol of the latent curing agent AMPU-CuBr2 prepared in Example 3, add 2 mol of bisphenol A epoxy resin and 2 mol of bisphenol A cyanate ester, and magnetically stir the pre-ligand reaction at 60°C for 30 min until a homogeneous matrix resin precursor solution is obtained;

[0095] Step 2: After removing air bubbles by ultrasonication, the matrix resin precursor liquid is poured into an aluminum mold;

[0096] Step 3: Perform segmented curing according to the following procedure: pre-curing at 80°C for 2 h, then heating the system to 120°C for 2 h, and finally curing at 150°C for 6 h to obtain the epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuBr2. Performance tests were performed on the cured product, and the results are shown in the table below.

[0097] Example 7: Preparation of epoxy-modified cyanate ester resin EPCE-SS-AMPU-Cu(NO3)2

[0098] Table 7. Raw materials used in the synthesis of epoxy-modified cyanate ester resin EP-SS-AMPU-Cu(NO3)2 in Example 7

[0099]

[0100] Preparation method:

[0101] Step 1: Weigh 1 mol of the disulfide bond curing agent SS prepared in Example 1, 1 mol of the latent curing agent AMPU-Cu(NO3)2 prepared in Example 4, add 2 mol of bisphenol A epoxy resin and 2 mol of bisphenol A cyanate, and magnetically stir the pre-ligand reaction at 60°C for 30 min until a homogeneous matrix resin precursor solution is obtained;

[0102] Step 2: After removing air bubbles by ultrasonication, the matrix resin precursor liquid is poured into an aluminum mold;

[0103] Step 3: Perform segmented curing according to the following procedure: pre-curing at 80°C for 2 h, then heating the system to 120°C for 2 h, and finally curing at 150°C for 6 h to obtain epoxy-modified cyanate ester resin EPCE-SS-AMPU-Cu(NO3)2. Performance tests were performed on the cured product, and the results are shown in the table below.

[0104] Comparative Example 1: Preparation of Epoxy-Modified Cyanate Ester Resin EPCE-AM

[0105] Table 8. Raw materials used in the synthesis of epoxy-modified cyanate ester resin EPCE-AM in Comparative Example 1

[0106]

[0107] Preparation method:

[0108] Step 1: Weigh 1 mol of 2,3-aminopyridine, 2 mol of bisphenol A epoxy resin and 2 mol of bisphenol A cyanate and mix them. Stir and react at 60°C for 30 min until a homogeneous matrix resin precursor solution is obtained.

[0109] Step 2: After removing air bubbles by ultrasonication, the matrix resin precursor liquid is poured into an aluminum mold;

[0110] Step 3: Perform segmented curing according to the following procedure: pre-cur at 80°C for 2 h, then raise the system temperature to 120°C for 2 h, and finally cure at 150°C for 6 h to obtain epoxy-modified cyanate ester resin EPCE-AM. Performance tests were performed on the cured product, and the results are shown in the table below.

[0111] Comparative Example 2: Preparation of Epoxy-Modified Cyanate Ester Resin EPCE-SS

[0112] Table 9. Raw materials used in the synthesis of epoxy-modified cyanate ester resin EPCE-SS in Comparative Example 2

[0113]

[0114] Preparation method:

[0115] Step 1: Weigh 1 mol of the disulfide bond curing agent SS prepared in Example 1, add 2 mol of bisphenol A epoxy resin and 2 mol of bisphenol A cyanate, and magnetically stir the pre-ligand reaction at 60°C for 30 min until a uniform matrix resin precursor solution is obtained.

[0116] Step 2: After removing air bubbles by ultrasonication, the matrix resin precursor liquid is poured into an aluminum mold;

[0117] Step 3: Perform segmented curing according to the following procedure: pre-cur at 80°C for 2 h, then raise the system temperature to 120°C for 2 h, and finally cure at 150°C for 6 h to obtain epoxy-modified cyanate ester resin EPCE-SS. Performance tests were performed on the cured product, and the results are shown in the table below.

[0118] Comparative Example 3: Preparation of epoxy-modified cyanate ester resin EPCE-AMPU-CuCl2

[0119] Table 10. Raw materials used in the synthesis of epoxy-modified cyanate ester resin EPCE-AMPU-CuCl2 in Comparative Example 3

[0120]

[0121] Preparation method:

[0122] Step 1: Weigh 1 mol of the latent curing agent AMPU-CuCl2 prepared in Example 2, add 2 mol of bisphenol A epoxy resin and 2 mol of bisphenol A cyanate, and magnetically stir the pre-ligand reaction at 60°C for 30 min until a uniform matrix resin precursor solution is obtained.

[0123] Step 2: After removing air bubbles by ultrasonication, the matrix resin precursor liquid is poured into an aluminum mold;

[0124] Step 3: Perform segmented curing according to the following procedure: pre-curing at 80°C for 2 h, then heating the system to 120°C for 2 h, and finally curing at 150°C for 6 h to obtain the epoxy-modified cyanate ester resin EPCE-AMPU-CuCl2. Performance tests were performed on the cured product, and the results are shown in the table below.

[0125] Application Example 1: Preparation of Carbon Fiber Composite Materials

[0126] Table 11 Raw materials used in the synthesis of carbon fiber composite materials in Application Example 1

[0127]

[0128] Preparation method:

[0129] Step 1: Using the epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2 precursor liquid from Example 5 as the matrix, carbon fiber fabric is impregnated by a vacuum-assisted resin infusion process.

[0130] Step 2: Perform segmented curing according to the following procedure: pre-curing at 80°C for 2 h, then heating the system to 120°C for 2 h, and finally curing at 150°C for 6 h to obtain EPCE-SS-AMPU-CuCl2 based carbon fiber composite material;

[0131] Step 3: Using the epoxy-modified cyanate ester resin EPCE-AM precursor liquid of Comparative Example 1 as the matrix, the carbon fiber fabric is impregnated by a vacuum-assisted resin infusion process.

[0132] Step 4: Perform segmented curing according to the following procedure: pre-curing at 80°C for 2 h, then heating the system to 120°C for 2 h, and finally curing at 150°C for 6 h to obtain EPCE-AM based carbon fiber composite material.

[0133] Performance comparison test results

[0134] The properties of the epoxy-modified cyanate ester resins prepared in Examples 5-7 and Comparative Examples 1-3 were tested, including tensile strength, elongation at break, toughness, and scratch healing. Each experiment was conducted in triplicate, and the average value was taken as the final result. The test results are shown in Table 12. The spectrum of the UV lamp used in the scratch healing test is shown below. Figure 1 As shown (Power: 31.3 mW / cm) 2 (Wavelength: 300-600 nm).

[0135] Table 12 Comparison of properties of epoxy-modified cyanate ester resin cured products

[0136]

[0137] The data in Table 12 shows that:

[0138] By comparing Example 5 (epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2), Comparative Example 2 (epoxy-modified cyanate ester resin EPCE-SS), and Comparative Example 3 (epoxy-modified cyanate ester resin EPCE-AMPU-CuCl2), when scratches appeared on the surfaces of all three resins, a UV lamp (power: 31.3 mW / cm²) was used. 2After irradiating the surface of epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2 with UV light (wavelength: 300-600 nm) for 0.5 hours, the scratches completely disappeared, demonstrating excellent self-healing ability. In contrast, epoxy-modified cyanate ester resin EPCE-SS required 4.5 hours of UV irradiation for scratch healing, and epoxy-modified cyanate ester resin EPCE-AMPU-CuCl2 required 4 hours of UV irradiation, indicating a longer repair time. This demonstrates that the metal ligands and dynamic disulfide bonds in epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2 form a multilayer energy dissipation structure, significantly enhancing its self-healing ability.

[0139] By comparing Examples 5 (epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2), 6 (epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuBr2), and 7 (epoxy-modified cyanate ester resin EPCE-SS-AMPU-Cu(NO3)2), it can be found that the introduction of different copper salts can increase tensile strength, toughness, and elongation at break, with the copper chloride system showing the most significant synergistic toughening effect. This is because the introduction of metal salts can form pyridine amine-metal ligands with pyridine amine compounds, which can induce microphase separation of polyurethane segments, effectively overcoming the intrinsic brittleness of the high crosslinking density network, thereby achieving a significant improvement in tensile strength, elongation at break, and toughness.

[0140] By comparing Example 5 (epoxy-modified cyanate resin EPCE-SS-AMPU-CuCl2), Comparative Example 1 (epoxy-modified cyanate resin EPCE-AM), Comparative Example 2 (epoxy-modified cyanate resin EPCE-SS), and Comparative Example 3 (epoxy-modified cyanate resin EPCE-AMPU-CuCl2), the results showed that the elongation at break and toughness of epoxy-modified cyanate resin EPCE-SS-AMPU-CuCl2 were increased by 303% and 421% respectively compared with epoxy-cyanate resin EPCE-AM; by 239% and 247% respectively compared with epoxy-modified cyanate resin EPCE-SS; and by 277% and 290% respectively compared with epoxy-modified cyanate resin EPCE-AMPU-CuCl2. Furthermore, the surface scratch healing time of epoxy-modified cyanate ester resin EPCE-SS-AMPU-CuCl2 is shorter than that of epoxy-cyanate ester resin EPCE-AM, epoxy-modified cyanate ester resin EPCE-SS, and epoxy-modified cyanate ester resin EPCE-AMPU-CuCl2, demonstrating excellent self-healing ability. This fully demonstrates that the dynamic disulfide bonds and pyridine amine-metal ligands in the resin constitute a multilayer energy dissipation structure, thereby achieving a synergistic improvement in toughness and self-healing ability.

[0141] The transverse fiber bundle tensile strength, interlaminar shear strength, and self-healing ability of the EPCE-SS-AMPU-CuCl2-based composite material and the EPCE-AM-based composite material in Application Example 1 were tested respectively. The test results are shown in Table 13.

[0142] Table 13 Comparison of interfacial properties of carbon fiber composites

[0143]

[0144] As can be seen from the data in Table 13:

[0145] The transverse fiber bundle tensile strength of the EPCE-SS-AMPU-CuCl2-based composite material reached 36.7 MPa, significantly higher than the 11.4 MPa of the EPCE-AM-based composite material. Furthermore, the interlaminar shear strength load-displacement curve of the EPCE-SS-AMPU-CuCl2-based composite material exhibited a broad and long ductile plateau, with a typical matrix cohesive failure mode. In contrast, the EP-AM-based composite material showed brittle interfacial debonding. This demonstrates that the resin of this invention can significantly improve the interfacial toughness and damage tolerance of the composite material. In addition, when scratches were generated on the surfaces of both the EPCE-SS-AMPU-CuCl2-based and EPCE-AM-based composite materials, a UV lamp (power: 31.3 mW / cm²) was used to test the surface strength. 2 The scratches completely disappeared after irradiation with a UV lamp (wavelength: 300-600 nm) for 0.5 h, indicating that the dynamic disulfide bonds have a self-healing effect; however, the EPCE-AM-based composite material does not contain dynamic disulfide bonds, and the scratches cannot be restored no matter how long the UV lamp is used for irradiation, and it does not have self-healing ability.

[0146] This invention is not limited to the raw materials and steps in the above embodiments. The above embodiments are only for the purpose of facilitating the understanding of the content of this invention.

Claims

1. A process for the preparation of a self-repairing toughened epoxy-modified cyanate ester resin, characterized by, The preparation method includes: 1) A polyurethane oligomer curing agent end-capped with 4,4'-diaminodiphenyl disulfide containing disulfide bonds is prepared as a disulfide bond-based curing agent; the raw materials for preparing the disulfide bond-based curing agent include 4,4'-diaminodiphenyl disulfide containing disulfide bonds and polyurethane oligomers, the raw materials for preparing the polyurethane oligomers include isophorone diisocyanate and polycaprolactone diol, and the structural formula of the disulfide bond-based curing agent is as follows: ； In the formula: n is a positive integer greater than or equal to 1; 2) Prepare pyridine-based latent curing agents by reacting 2,2-dihydroxymethylbutyric acid, pyridine amine compounds, metal salts and isocyanate-terminated polyurethane oligomers; 3) A matrix resin precursor solution is obtained by pre-coordination reaction of disulfide bond curing agent, pyridine latent curing agent and matrix resin. The matrix resin includes epoxy resin and cyanate ester resin. The self-healing toughened epoxy modified cyanate ester resin is obtained by staged curing.

2. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The raw materials for preparing the polyurethane oligomer include diisocyanate, polyol, and catalyst. The number average molecular weight of the polyurethane oligomer is 1,000 to 20,000 g / mol. The diisocyanate is selected from at least one of aliphatic, alicyclic, or aromatic diisocyanates. The polyol is selected from at least one of polyester glycol, polyether glycol, or polycarbonate glycol with a number average molecular weight of 500 to 5,000 g / mol. The amount of catalyst added is 1% to 3% of the total mass of diisocyanate and polyol. The molar ratio of diisocyanate to polyol is (1.8 to 2.2): (0.9 to 1.1).

3. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The molar ratio of the 4,4'-diaminodiphenyl disulfide to the diisocyanate used to synthesize the polyurethane oligomer is 1:(1.8~2.2).

4. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The pyridine amine compound is selected from at least one of 2-aminopyridine, 2,3-aminopyridine, 4-aminopyridine, 3-aminopyridine-2-carboxamide, or 2-mercapto-3-aminopyridine; the molar ratio of the pyridine amine compound, 2,2-dihydroxymethylbutyric acid, and the diisocyanate used to synthesize the polyurethane oligomer is (0.5~1): (0.5~0.7): (1.8~2.2).

5. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The metal salt is selected from at least one of copper salt, zinc salt, nickel salt or iron salt; wherein the copper salt is selected from copper chloride, copper nitrate, copper bromide, copper sulfate, copper acetate or copper trifluoromethanesulfonate; the molar ratio of the metal ion in the metal salt to the nitrogen atom on the pyridine ring in the pyridine-based latent curing agent is 1:(1~3).

6. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The epoxy resin is at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin or alicyclic epoxy resin; the cyanate ester resin is selected from at least one of bisphenol A type cyanate ester, bisphenol E type cyanate ester, bisphenol M type cyanate ester, tetramethylbisphenol F type cyanate ester, phenolic type cyanate ester or dicyclopentadiene type cyanate ester.

7. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The molar ratio of the epoxy group in the epoxy resin to the active hydrogen on the amino group on the benzene ring in the disulfide bond curing agent is 1:(0.5~1.5); the molar ratio of the epoxy group in the epoxy resin to the active hydrogen on the amino group on the pyridine ring in the pyridine latent curing agent is 1:(0.5~1.5); the molar ratio of the cyanate group in the cyanate ester resin to the epoxy group in the epoxy resin is 1:(1~1.5).

8. The preparation method of the self-healing and toughened epoxy-modified cyanate ester resin as described in claim 1, characterized in that, The preparation method includes: 1) Diisocyanate, polyol and catalyst are blended and reacted under mechanical stirring at 40°C~70°C for 2~6 h to obtain isocyanate-terminated polyurethane prepolymer; 2) Dissolve 4,4'-diaminodiphenyl disulfide in anhydrous N,N-dimethylformamide, add it to isocyanate-terminated polyurethane prepolymer, and continue the reaction at 40°C ~ 60°C for 10 ~ 15 h to obtain disulfide bond curing agent SS; 3) Dissolve 2,2-dimethylolbutyric acid and pyridine amine compounds in anhydrous N,N-dimethylformamide, add them to isocyanate-terminated polyurethane prepolymer, and continue the reaction at 40°C~60°C for 10~15 h to obtain pyridine amine-terminated linear prepolymer; blend the pyridine amine-terminated linear prepolymer with a metal salt and mix at 50°C~70°C for 10~30 min to obtain a pyridine-based latent curing agent; 4) The disulfide bond curing agent, pyridine amine latent curing agent, epoxy resin and cyanate ester resin are subjected to a pre-coordination reaction at 40~100°C for 10~40 min; the matrix resin is added and mixed at 40~100°C for 20~40 min to obtain the matrix resin precursor solution. 5) The matrix resin precursor liquid is cured in stages: first, it is pre-cured at 70~90°C for 1~3 h, then cured at 110~130°C for 1~3 h, and finally post-cured at 140~160°C for 4~8 h to obtain self-healing toughened epoxy modified cyanate resin.

9. The application of a self-healing and toughened epoxy-modified cyanate ester resin prepared by any one of claims 1-8 in the field of lightweight automotive structural components or radar transparent structural components.

10. The application according to claim 9, characterized in that, The self-healing and toughened epoxy-modified cyanate ester resin is used as the matrix resin to impregnate carbon fiber fabric and then cured to prepare carbon fiber composite material, which is used as a lightweight structural component for automobiles or a radar-transparent structural component.

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