A high toughness epoxy resin composition and process for making

Abstract

The application discloses a high-toughness epoxy resin composition and a preparation process, and particularly relates to the field of modified epoxy resin, and comprises the following steps: 5-15 electrostatic spinning nanofiber prepregs are compounded with an epoxy resin matrix containing dynamic covalent bonds (furan / bismaleimide), and 10-15 SiO2 / poly-sulfur shell-core particles are added; the resin viscosity is regulated to 800 mPa·s through pre-reaction, and a step curing process is combined to realize fiber dispersion and interface strengthening. Through the synergistic effect of the interlayer reinforcement of nanofibers, the energy dissipation of dynamic bonds and the crack pinning of core-shell particles, the impact strength and the bending strength are significantly improved, the self-repairing potential is possessed, the process stability is high, the problems of fiber swelling, multiphase interface deterioration and internal stress accumulation in the traditional process are solved, and the performance single and interface deterioration bottleneck of the traditional toughening scheme are broken through.

Description

Technical Field

[0001] This invention relates to the field of modified epoxy resins, and particularly to a high-toughness epoxy resin composition and its preparation process. Background Technology

[0002] Epoxy resins are widely used in aerospace, electronic packaging, and composite materials due to their excellent adhesion, chemical resistance, and dimensional stability. However, traditional epoxy resins have high crosslinking density and brittleness after curing, making them prone to brittle fracture under impact loads, which limits their application in dynamic load-bearing scenarios. Therefore, the industry has conducted extensive research on "toughening modification," but existing technologies still face the following bottlenecks:

[0003] 1. Limitations of a single toughening mechanism

[0004] Elastomer toughening: Adding rubber particles (such as CTBN) induces crazing and energy dissipation, but it leads to a significant decrease in material rigidity (tensile strength decreases by 30%~50%) and prominent phase separation problems.

[0005] Nanoparticle filling: Nano-SiO2, carbon nanotubes and other materials are used to improve toughness, but high addition amounts (>10wt%) can easily cause agglomeration and create stress concentration points.

[0006] Thermoplastic resin blends, such as PEI and PES, can improve toughness, but they have high processing temperatures (>300℃) and are incompatible with epoxy curing processes.

[0007] 2. The trade-off between self-healing function and mechanical properties

[0008] While the introduction of dynamic covalent bonds (such as Diels-Alder bonds and disulfide bonds) endows materials with self-healing capabilities, flexible segments reduce crosslinking density, leading to a decrease in material strength. Furthermore, the self-healing efficiency of traditional dynamic networks relies on high-temperature / long-duration stimulation (e.g., 120℃ / 2h), which is insufficient for practical working conditions.

[0009] 3. Challenges in process compatibility and internal stress control

[0010] In traditional toughening processes, blending nanomaterials significantly increases resin viscosity, limiting the uniform implantation of fiber reinforcement layers. Simultaneously, the accumulation of thermal stress during the curing stage can easily induce microcracks, reducing the material's service life.

[0011] To address the aforementioned issues, this invention proposes a multi-scale synergistic toughening epoxy resin system. Through a triple mechanism of nanofiber interlayer reinforcement, dynamic covalent bond energy dissipation, and core-shell particle crack pinning, it breaks through the technical limitations of single-component toughening. Furthermore, through innovative electrospinning in-situ composite and stepped curing processes, it solves problems such as poor nanomaterial dispersion, weak interfacial bonding, and internal stress accumulation, achieving a balance between high toughness, high strength, and self-healing capabilities, filling a gap in existing technologies. Summary of the Invention

[0012] The main objective of this invention is to provide a high-toughness epoxy resin composition and its preparation process, which can effectively solve the problems in the prior art.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0014] A high-toughness epoxy resin composition comprising the following components in parts by weight:

[0015] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0016] Dynamic covalent network components: 10-20 parts of furanyl glycidyl ether, 3-8 parts of bismaleimide;

[0017] Nanofiber reinforced prepreg: 5-15 layers of electrospun nanofibers;

[0018] Reactive core-shell particles: 10-15 parts of SiO2 / polysulfide core-shell particles;

[0019] Curing agent: 20-30 parts of 4,4'-diaminodiphenylmethane, 0.1-0.5 parts of triphenylphosphine;

[0020] Coupling agent: 0.5-3 parts of γ-glycidyl oxypropyltrimethoxysilane;

[0021] Defoamer: BYK-066N surfactant 0.1-0.5 parts.

[0022] A process for preparing the above-mentioned high-toughness epoxy resin composition includes the following specific steps:

[0023] Step 1: Material Preparation and Pretreatment

[0024] SiO2 / polysulfide core-shell particles were synthesized to prepare polyimide spinning solution and nanofiber reinforced prepreg.

[0025] Step 2, Prepreg Pretreatment:

[0026] The nanofiber-reinforced prepreg was immersed in a 1 wt% γ-glycidyl etheroxypropyltrimethoxysilane coupling agent ethanol solution for 5 min, and then dried at 80°C for 30 min to enhance the fiber-resin interface bonding.

[0027] Step 3, Dynamic covalent network pre-reaction:

[0028] Furan glycidyl ether, bismaleimide, and triphenylphosphine were added to a three-necked flask and stirred in an oil bath at 60°C for 30 min. The viscosity of the system decreased from 2000 mPa·s to 800 mPa·s.

[0029] Step 4, Mixing and Dispersing:

[0030] Bisphenol F epoxy resin, pre-reacted furan glycidyl ether / bismaleimide system, SiO2 / polysulfide core-shell particles, γ-glycidyl etheroxypropyltrimethoxysilane coupling agent ethanol solution impregnated with nanofiber reinforced prepreg, and BYK-066N surfactant were added to a planetary mixer and stirred at 500 rpm for 15 min. Then, vacuum degassing was performed for 10 min, and then 4,4'-diaminodiphenylmethane was added and stirred at 200 rpm for 5 min.

[0031] Step 5, Step-by-Step Curing and Molding:

[0032] The material obtained in step 4 is subjected to three stages: pre-curing, primary curing, and post-curing molding, to obtain the high-toughness epoxy resin composition.

[0033] Preferably, the specific preparation method of the SiO2 / polysulfide core-shell particles is as follows:

[0034] Step 101: Using tetraethyl orthosilicate as a precursor, it was added to an ethanol / water mixture and stirred at 400 rpm under oil bath temperature control at 50.0℃±0.5℃. 5.0 mL of ammonia water (25% NH3) was slowly added dropwise at a rate of 1 mL / min through a constant pressure dropping funnel, and the reaction was continued for 6 h. After the reaction was completed, the product was centrifuged and ultrasonically washed three times with ethanol (200 mL each time, ultrasonic frequency 40 kHz, 5 min each time). Then it was vacuum dried at 60℃ for 12 h to obtain SiO2 nanoparticles with uniform particle size.

[0035] Step 102, Thiolization modification: SiO2 nanoparticles were dispersed in toluene, 3-mercaptopropyltrimethoxysilane was added, and the mixture was refluxed at 80.0℃ under nitrogen protection for 12 h to achieve surface thiol functionalization;

[0036] Step 103, ATRP polymerization: Thiolized SiO2, allyl thioacetate, and CuBr / PMDETA catalyst were added to the reaction system. After purging with nitrogen at a flow rate of 20 mL / min for 30 min, the system was sealed and surface-initiated atom transfer radical polymerization was carried out at 60.0 °C for 24 h. The final product was centrifuged, washed with toluene, and vacuum dried to obtain core-shell structured SiO2 / polysulfide particles.

[0037] Preferably, in the ethanol / water mixture added in step 101, the volume ratio of ethanol to deionized water is 4:1.

[0038] Preferably, in step 101, the parameters for centrifuging the product are as follows: centrifuge at 8000 rpm for 10 minutes.

[0039] Preferably, the polyimide spinning solution is prepared as follows:

[0040] Polyimide powder was added to a dimethylacetamide / acetone mixed solvent (mass ratio 7:3) and magnetically stirred at 50°C for 6 hours until completely dissolved. The resulting solution was filtered through a 200-mesh filter to remove undissolved particles and impurities, thus obtaining a polyimide spinning solution.

[0041] Preferably, the nanofiber reinforced prepreg is prepared as follows:

[0042] The spinning process is driven by a bipolar high-voltage power supply. Polyimide spinning solution is injected into a spinneret with an inner diameter of 0.51 mm at a flow rate of 1.0 mL / h. The spinneret is kept at a receiving distance of 15 cm on the surface of bisphenol F type epoxy resin prepreg and is reciprocated at a speed of 10 cm / s to uniformly deposit 5-15 layers of fiber. The thickness of a single fiber layer is about 8 μm. After the total deposition, the fiber is vacuum dried at 60 °C for 2 hours to remove solvent residue.

[0043] Preferably, when preparing the nanofiber-reinforced prepreg, the deposition interval between each layer is 30 seconds to ensure that the resin prepreg fully wets the fiber network.

[0044] Preferably, the specific parameters for the stepped curing stage in step 5 are as follows:

[0045] Pre-curing: Temperature 80℃±0.5℃, heating rate 2℃ / min, holding time 2h±5min;

[0046] Main curing: Temperature 120℃±0.5℃, heating rate 3℃ / min, holding time 1h±3min;

[0047] Post-curing: Temperature 160℃±1.0℃, heating rate 5℃ / min, holding time 0.5h±2min, and completed under vacuum of -0.08MPa.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. This invention is based on the synergistic effect of a triple mechanism: interlayer reinforcement by nanofibers, energy dissipation from dynamic covalent bonds, and crack pinning by core-shell particles. The material exhibits excellent energy absorption capacity under impact loads. The high modulus of nanofibers effectively transfers stress, the reversible fracture of dynamic bonds dissipates crack propagation energy, and the core-shell particles delay the fracture process through interfacial debonding and bridging. The synergistic effect of these three mechanisms significantly improves the material's toughness and damage resistance, while avoiding the rigidity loss caused by a single toughening mechanism, achieving a balanced optimization of high strength and high toughness.

[0050] 2. The design of the dynamic covalent network in this invention balances self-healing efficiency with matrix rigidity. The dynamic bonds can rapidly recombine under mild conditions (such as short-term heating at 80°C), achieving efficient repair of the damaged area. Furthermore, the rigid main network remains stable during the repair process, avoiding the modulus decrease caused by excessive flexible segments in traditional self-healing materials. In addition, the chemical synergy between the active groups on the core-shell particle surface and the dynamic bonds further enhances the bonding strength at the repair interface, ensuring stable mechanical properties after multiple repairs.

[0051] 3. The innovative pre-reaction-step curing process of this invention resolves the conflict between high-viscosity systems and the preservation of nanofiber structures. Pre-crosslinking of the dynamic network reduces resin viscosity, ensuring the morphological integrity of the electrospun fibers; the step-curing process effectively releases internal stress and suppresses microcrack formation by controlling dynamic bond recombination and main network crosslinking in stages. The resulting material has very few internal defects and dense interfacial bonding, meeting the requirements for high-precision molding.

[0052] 4. In this invention, the hydrogen bonding interaction between the functional groups on the nanofiber surface and the dynamic bonds, and the covalent coupling between the thiol groups and epoxy groups of the core-shell particles, jointly construct a strong interfacial bonding network across scales. This interfacial synergy not only improves stress transfer efficiency but also achieves multi-level energy dissipation through the breaking and recombination behavior of dynamic bonds, enabling the material to exhibit excellent fatigue and impact resistance under complex loads. Detailed Implementation

[0053] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0054] In the process of in-depth exploration of the synergistic design of epoxy resin toughening and functionalization, the inventors discovered, through systematic literature review and testing, that although existing technologies have achieved the development of single functional modules such as electrospun nanofiber layer reinforcement, dynamic covalent bond self-healing network construction, and core-shell particle stress dissipation, their technical solutions are all limited to single-dimensional performance optimization, and there are significant technical gaps and theoretical contradictions in the multi-factor synergistic mechanism, specifically manifested as follows:

[0055] Existing research confirms that the morphological integrity of electrospun nanofibers is highly dependent on the low viscosity of the matrix resin (typically requiring <500 mPa·s). However, the introduction of dynamic covalent bonds (such as in the Diels-Alder system) can cause the resin viscosity to surge to 2000-3000 mPa·s, and the dispersion of core-shell particles further exacerbates the rheological degradation of the system. This contradiction leads to the swelling and collapse of nanofibers (fiber diameter deviation >50%) under traditional blending processes, resulting in the loss of reinforcing effect.

[0056] Furthermore, the flexible segments in dynamic covalent networks (such as the furan-maleimide dynamic bond with an entanglement length of approximately 8-12 nm) significantly reduce the material's rigidity, while the stress transfer efficiency between nanofibers and core-shell particles relies on a highly rigid matrix. Existing technologies have failed to resolve this rigidity-toughness balance paradox, resulting in the actual performance of the synergistic system being lower than the theoretical superposition value.

[0057] Therefore, the inventors provide a high-toughness epoxy resin composition that overcomes the above-mentioned technical obstacles, specifically comprising the following components:

[0058] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0059] Dynamic covalent network components: 10-20 parts of furanyl glycidyl ether, 3-8 parts of bismaleimide;

[0060] Nanofiber reinforced prepreg: 5-15 layers of electrospun nanofibers;

[0061] Reactive core-shell particles: 10-15 parts of SiO2 / polysulfide core-shell particles;

[0062] Curing agent: 20-30 parts of 4,4'-diaminodiphenylmethane, 0.1-0.5 parts of triphenylphosphine;

[0063] Coupling agent: 0.5-3 parts of γ-glycidyl oxypropyltrimethoxysilane;

[0064] Defoamer: BYK-066N surfactant 0.1-0.5 parts.

[0065] It should be noted that in this invention, the SiO2 / polysulfide core-shell particles are prepared in the following manner:

[0066] Step 101: Using tetraethyl orthosilicate as a precursor, it was added to an ethanol / water mixture (volume ratio 4:1, 200 mL ethanol + 50 mL deionized water) and stirred at 400 rpm under oil bath temperature control at 50.0℃±0.5℃. 5.0 mL ammonia water (25% NH3) was slowly added dropwise at a rate of 1 mL / min through a constant pressure dropping funnel and the reaction was continued for 6 h. After the reaction was completed, the product was centrifuged (8000 rpm×10 min, centrifuge Sigma3-18KS, rotor number 12150) and ultrasonically washed three times with ethanol (200 mL each time, ultrasonic frequency 40 kHz, 5 min each time). Then it was vacuum dried at 60℃ for 12 h to obtain SiO2 nanoparticles with uniform particle size.

[0067] Step 102, Thiolization modification: SiO2 nanoparticles were dispersed in toluene, 3-mercaptopropyltrimethoxysilane was added, and the mixture was refluxed at 80.0℃ under nitrogen protection for 12 h to achieve surface thiol functionalization;

[0068] Step 103, ATRP polymerization: Thiolized SiO2, allyl thioacetate, and CuBr / PMDETA catalyst were added to the reaction system. After purging with nitrogen at a flow rate of 20 mL / min for 30 min, the system was sealed and surface-initiated atom transfer radical polymerization was carried out at 60.0 °C for 24 h. The final product was centrifuged, washed with toluene, and vacuum dried to obtain core-shell structured SiO2 / polysulfide particles.

[0069] Furthermore, the preparation method of the polyimide spinning solution is as follows:

[0070] Polyimide powder was added to a dimethylacetamide / acetone mixed solvent (mass ratio 7:3) and magnetically stirred at 50°C for 6 hours until completely dissolved. The resulting solution was filtered through a 200-mesh filter to remove undissolved particles and impurities, thus obtaining a polyimide spinning solution.

[0071] The specific method for preparing nanofiber-reinforced prepreg using the above-mentioned polyimide spinning solution is as follows:

[0072] The spinning process is driven by a bipolar high-voltage power supply. Polyimide spinning solution is injected into a spinneret with an inner diameter of 0.51 mm at a flow rate of 1.0 mL / h. The spinneret is kept at a receiving distance of 15 cm on the surface of bisphenol F type epoxy resin prepreg and is reciprocated at a speed of 10 cm / s to uniformly deposit 5-15 layers of fiber. The thickness of a single fiber layer is about 8 μm. After the total deposition, the fiber is vacuum dried at 60 °C for 2 hours to remove solvent residue.

[0073] It should be noted that when preparing the nanofiber-reinforced prepreg, the deposition interval between each layer is 30 seconds to ensure that the resin prepreg fully wets the fiber network.

[0074] The present invention is further disclosed below with reference to specific embodiments and comparative examples: Examples 1-5 are specific methods for preparing high-toughness epoxy resin compositions after adjusting other materials except that the amount of bisphenol F epoxy resin is 100 parts; Comparative Example 1 is a high-toughness epoxy resin composition prepared without adding nanofiber reinforced prepreg based on Example 1; Comparative Example 2 is a high-toughness epoxy resin composition prepared without adding SiO2 / polysulfide core-shell particles based on Example 1; Comparative Example 3 is an epoxy resin composition prepared without adding a dynamic covalent network pre-reaction system based on Example 1.

[0075] Example 1

[0076] The raw materials used in this embodiment are as follows, by weight:

[0077] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0078] Dynamic covalent network components: 15 parts furanyl glycidyl ether, 5 parts bismaleimide;

[0079] Nanofiber reinforced prepreg: 8 layers of electrospun nanofibers;

[0080] Reactive core-shell particles: 12 parts of SiO2 / polysulfide core-shell particles;

[0081] Curing agent: 25 parts 4,4'-diaminodiphenylmethane, 0.3 parts triphenylphosphine;

[0082] Coupling agent: 1.5 parts of γ-glycidoxypropyltrimethoxysilane;

[0083] Defoamer: 0.3 parts of BYK-066N surfactant.

[0084] Based on the above-mentioned raw materials, this embodiment prepares a high-toughness epoxy resin composition according to the following steps:

[0085] Step 1: Material Preparation and Pretreatment

[0086] SiO2 / polysulfide core-shell particles were synthesized to prepare polyimide spinning solution and nanofiber reinforced prepreg.

[0087] Step 2, Prepreg Pretreatment:

[0088] The nanofiber-reinforced prepreg was immersed in a 1 wt% γ-glycidyl etheroxypropyltrimethoxysilane coupling agent ethanol solution for 5 min, and then dried at 80°C for 30 min to enhance the fiber-resin interface bonding.

[0089] Step 3, Dynamic covalent network pre-reaction:

[0090] Furan glycidyl ether, bismaleimide, and triphenylphosphine were added to a three-necked flask and stirred in an oil bath at 60°C for 30 min. The viscosity of the system decreased from 2000 mPa·s to 800 mPa·s.

[0091] Step 4, Mixing and Dispersing:

[0092] Bisphenol F epoxy resin, pre-reacted furan glycidyl ether / bismaleimide system, SiO2 / polysulfide core-shell particles, γ-glycidyl etheroxypropyltrimethoxysilane coupling agent ethanol solution impregnated with nanofiber reinforced prepreg, and BYK-066N surfactant were added to a planetary mixer and stirred at 500 rpm for 15 min. Then, vacuum degassing was performed for 10 min, and then 4,4'-diaminodiphenylmethane was added and stirred at 200 rpm for 5 min.

[0093] Step 5, Step-by-Step Curing and Molding:

[0094] The material obtained in step 4 is subjected to three stages: pre-curing, main curing, and post-curing molding, to obtain the high-toughness epoxy resin composition.

[0095] The specific parameters for the stepped curing stage are as follows:

[0096] Pre-curing: Temperature 80℃±0.5℃, heating rate 2℃ / min, holding time 2h±5min;

[0097] Main curing: Temperature 120℃±0.5℃, heating rate 3℃ / min, holding time 1h±3min;

[0098] Post-curing: Temperature 160℃±1.0℃, heating rate 5℃ / min, holding time 0.5h±2min, and completed under vacuum of -0.08MPa.

[0099] Example 2

[0100] This embodiment is based on Example 1, only adjusting the proportions of each component raw material. The preparation steps are exactly the same as in Example 1, specifically:

[0101] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0102] Dynamic covalent network components: 10 parts of furanyl glycidyl ether, 3 parts of bismaleimide;

[0103] Nanofiber reinforced prepreg: 5 layers of electrospun nanofibers;

[0104] Reactive core-shell particles: 10 parts of SiO2 / polysulfide core-shell particles;

[0105] Curing agent: 20 parts of 4,4'-diaminodiphenylmethane, 0.1 parts of triphenylphosphine;

[0106] Coupling agent: 0.5 parts of γ-glycidoxypropyltrimethoxysilane;

[0107] Defoamer: 0.1 parts of BYK-066N surfactant.

[0108] Example 3

[0109] This embodiment is based on Example 1, only adjusting the proportions of each component raw material. The preparation steps are exactly the same as in Example 1, specifically:

[0110] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0111] Dynamic covalent network components: 20 parts of furanyl glycidyl ether, 8 parts of bismaleimide;

[0112] Nanofiber reinforced prepreg: 15 layers of electrospun nanofibers;

[0113] Reactive core-shell particles: 15 parts of SiO2 / polysulfide core-shell particles;

[0114] Curing agent: 30 parts 4,4'-diaminodiphenylmethane, 0.5 parts triphenylphosphine;

[0115] Coupling agent: 3 parts of γ-glycidoxypropyltrimethoxysilane;

[0116] Defoamer: 0.5 parts of BYK-066N surfactant.

[0117] Example 4

[0118] This embodiment is based on Example 1, only adjusting the proportions of each component raw material. The preparation steps are exactly the same as in Example 1, specifically:

[0119] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0120] Dynamic covalent network components: 12 parts of furanyl glycidyl ether and 4 parts of bismaleimide;

[0121] Nanofiber reinforced prepreg: 8 layers of electrospun nanofibers;

[0122] Reactive core-shell particles: 11 parts of SiO2 / polysulfide core-shell particles;

[0123] Curing agent: 22 parts of 4,4'-diaminodiphenylmethane, 0.25 parts of triphenylphosphine;

[0124] Coupling agent: 1 part of γ-glycidoxypropyltrimethoxysilane;

[0125] Defoamer: 0.2 parts of BYK-066N surfactant.

[0126] Example 5

[0127] This embodiment is based on Example 1, only adjusting the proportions of each component raw material. The preparation steps are exactly the same as in Example 1, specifically:

[0128] Resin matrix: 100 parts of bisphenol F epoxy resin;

[0129] Dynamic covalent network components: 18 parts of furanyl glycidyl ether and 7 parts of bismaleimide;

[0130] Nanofiber reinforced prepreg: 13 layers of electrospun nanofibers;

[0131] Reactive core-shell particles: 14 parts of SiO2 / polysulfide core-shell particles;

[0132] Curing agent: 27 parts 4,4'-diaminodiphenylmethane, 0.4 parts triphenylphosphine;

[0133] Coupling agent: 2 parts of γ-glycidoxypropyltrimethoxysilane;

[0134] Defoamer: 0.4 parts of BYK-066N surfactant.

[0135] Comparative Example 1

[0136] The only difference between this comparative example and Example 1 is that:

[0137] In terms of raw material selection: high-toughness epoxy resin composition is prepared without adding nanofiber reinforced prepreg.

[0138] The difference between this comparative example and Example 1 in terms of preparation steps is as follows: in step 1, it is not necessary to prepare polyimide spinning solution and nanofiber reinforced prepreg during pretreatment; the entire step 2 is deleted; and in step 4, it is not necessary to add γ-glycidyl etheroxypropyltrimethoxysilane coupling agent ethanol solution to impregnate nanofiber reinforced prepreg during mixing and dispersion.

[0139] All other ingredients and steps remain unchanged.

[0140] Comparative Example 2

[0141] The only difference between this comparative example and Example 1 is that:

[0142] In terms of raw material selection: SiO2 / polysulfide core-shell particles are not added;

[0143] Regarding the preparation steps: in step 1, there is no need to synthesize SiO2 / polysulfide core-shell particles during pretreatment; in step 4, there is also no need to add SiO2 / polysulfide core-shell particles during mixing and dispersion.

[0144] All other ingredients and steps remain unchanged.

[0145] Comparative Example 3

[0146] The only difference between this comparative example and Example 1 is that:

[0147] Regarding the selection of raw materials: dynamic covalent network pre-reaction system;

[0148] Regarding the preparation steps: the entire step 2 is deleted; in step 4, during mixing and dispersion, it is also unnecessary to add the pre-reacted furan glycidyl ether / bismaleimide system.

[0149] All other ingredients and steps remain unchanged.

[0150] Based on Examples 1-5 and Comparative Examples 1-3 above, the following performance tests were conducted:

[0151] I. Impact Toughness Test

[0152] Impact strength was tested according to ASTM D6110 standard:

[0153] The finished products prepared in Examples 1-5 and Comparative Examples 1-3 were respectively molded into V-notch specimens with a length of 80 mm × width of 10 mm × thickness of 4 mm (notch depth 2 mm, radius 0.25 mm). Ten parallel specimens were prepared for each group, and the surface was polished to Ra≤0.8 μm. The test results are shown in Table 1.

[0154] Table 1: Impact toughness test results of Examples 1-5 and Comparative Examples 1-3

[0155]

[0156] As can be seen from the results in Table 1, the samples prepared in Examples 1-5 have the highest impact strength, reaching (52.4-60.1 kJ / m²), while the impact strength of Comparative Example 1, which did not contain nanofiber reinforced prepreg, drops sharply.

[0157] Although nanofiber-reinforced prepregs were present in Comparative Examples 2 and 3, SiO2 / polysulfide core-shell particles and dynamic covalent network pre-reaction system were not added, and their impact strength was significantly reduced, but still better than that of Comparative Example 1. The reason is that the core-shell particles toughen the cracks through crack deflection and bridging, while the reversible cross-linking of the dynamic covalent network after fracture inhibits crack propagation and has a certain toughening effect. The synergistic effect of the three results in the best overall performance of Example 1.

[0158] In addition, the standard deviations of Examples 1-5 and Comparative Examples 1-3 are also quite different, indicating that the synergistic effect of nanofibers and core-shell particles can significantly improve the material uniformity and stabilize the sample performance. However, the standard deviation of Comparative Example 1, ±3.2, shows that without the addition of nanofibers, microcracks or interface defects are easily generated inside the material, resulting in large performance differences between samples.

[0159] II. Dynamic Thermomechanical Analysis

[0160] Sample preparation: After curing, the plate was cut into samples measuring 35mm in length, 10mm in width, and 2mm in thickness, and the surface was polished.

[0161] Test equipment: TA Instruments Q800DMA, three-point bending mode

[0162] Test parameters: temperature range 30-250℃, heating rate 3℃ / min, frequency 1Hz, strain 0.05%.

[0163] Test standard: Refer to ASTM D4065; Test results are shown in Table 2.

[0164] Table 2. Dynamic thermomechanical analysis test results of Examples 1-5 and Comparative Examples 1-3

[0165]

[0166] As can be seen from the test results in Table 2, Examples 1-5 all have high Tg and E' retention rates, while Comparative Example 3 has a Tg of only 142°C and an E' retention rate of 65.4%. This shows that insufficient crosslinking density leads to a sharp drop in high-temperature modulus.

[0167] Meanwhile, the Tg in Example 3 was increased to 165°C, proving that increasing the dynamic network content can optimize thermal stability; Comparative Example 2 (without core-shell particles): E' retention rate was 73.8%, proving that core-shell particles inhibit molecular chain slippage at high temperatures through interface reinforcement.

[0168] III. Three-point bending strength test

[0169] Test standard: Refer to ASTM D790

[0170] Sample preparation: 80mm×10mm×4mm standard sample was molded with a span of 64mm.

[0171] Test equipment: Instron 5969 universal testing machine, 50kN load sensor.

[0172] Test parameters: loading rate 2 mm / min, load-displacement curve recorded until fracture. Test results are shown in Table 3.

[0173] Table 3: Three-point bending strength test results of Examples 1-5 and Comparative Examples 1-3

[0174]

[0175] The test results in Table 3 show that the samples prepared in Examples 1-5 all have high flexural strength and elongation at break, while the flexural strength in Comparative Example 2 is significantly reduced. This is because the core-shell particles (SiO2 / polysulfide) hinder crack propagation through the "pinning effect," thus having a toughening effect. In Comparative Example 1, the flexural modulus is 2.78 GPa, indicating that fiber reinforcement increases the modulus by about 15.5%. In Comparative Example 3, the elongation at break is 3.5%, which shows that the dynamic network delays fracture through reversible bond recombination.

[0176] As can be seen from the above:

[0177] This invention introduces a dynamic covalent network pre-reaction (step 3 in the preparation process), in which furan glycidyl ether and bismaleimide are pre-reacted for 30 minutes, reducing the resin viscosity from 2000 mPa·s to 800 mPa·s, which is suitable for the requirements of electrospinning process (500-1000 mPa·s). As can be seen from the results in Test 1, the standard deviations of Examples 1-5 are all low. The pre-reaction system maintains the integrity of fiber morphology and reinforcement effect while maintaining low viscosity, breaking through the limitation of fiber failure caused by high viscosity in traditional processes.

[0178] Furthermore, by adjusting the ratio of rigid aromatic rings (bismaleimide) to flexible ether bonds (furan) in the dynamic network (3-8 parts), a cross-linked network with both rigidity and flexibility is formed. In Example 1, the flexural modulus reached 3.21 GPa (15% higher than that of the ordinary DA system), and the elongation at break was 5.7% (63% higher than that of Comparative Example 3), achieving compatibility between rigid matrix and flexible energy dissipation, and filling the theoretical gap of "toughening and strengthening" of dynamic networks.

[0179] In addition, this invention achieves chemical bonding (Si-OC) by using a coupling agent gradient treatment (steps 2+4), pretreating the fibers with γ-glycidyl ether, and grafting thioether bonds (-S-) onto the surface of the core-shell particles. The interfacial chemical bonding inhibits phase separation, and the synergistic dispersion efficiency of the core-shell particles and fibers is improved, thus overcoming the industry problem of interfacial weakening in multi-component composite materials.

[0180] The present invention also designs a stepped curing process (step 5), which involves phased heating (pre-curing at 80℃ → main curing at 120℃ → post-curing at 160℃) to gradually release internal stress and further enhance the toughness of the finished product.

[0181] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A high toughness epoxy resin composition, characterized by, The following components are included by weight parts: Resin matrix: bisphenol F type epoxy resin 100 parts; Dynamic covalent network component: furan glycidyl ether 10-20 parts, bismaleimide 3-8 parts; Nanofiber reinforced prepreg: Bisphenol F type epoxy resin prepreg with 5-15 layers of polyimide nanofiber deposited by electrospinning process, the single layer fiber thickness of the polyimide nanofiber is about 8 μm; Reactive core-shell particles: SiO2 / polythioether core-shell particles 10-15 parts; Curing agent: 4,4'-diaminodiphenylmethane 20-30 parts, triphenylphosphine 0.1-0.5 parts; Coupling agent: γ-glycidyloxypropyltrimethoxysilane 0.5-3 parts; Defoaming agent: BYK-066N surfactant 0.1-0.5 parts.

2. A method of producing the high toughness epoxy resin composition according to claim 1, characterized by, The specific steps are as follows Step 1, material preparation and pretreatment: Synthesis of SiO2 / polythioether core-shell particles, preparation of polyimide spinning solution, and preparation of nanofiber reinforced prepreg; Step 2, prepreg pretreatment: Immerse the nanofiber reinforced prepreg in a 1wt% γ-glycidyloxypropyltrimethoxysilane coupling agent ethanol solution for 5 min, then take it out and dry it at 80℃ for 30 min to enhance the fiber-resin interface bonding; Step 3, dynamic covalent network pre-reaction: Add furan glycidyl ether, bismaleimide, and triphenylphosphine into a three-necked flask, stir and react at 60℃ oil bath for 30 min, the viscosity of the system decreases from 2000 mPa·s to 800 mPa·s; Step 4, mixing and dispersion: Add bisphenol F epoxy resin, pre-reacted furan glycidyl ether / bismaleimide system, SiO2 / polythioether core-shell particles, γ-glycidyloxypropyltrimethoxysilane coupling agent ethanol solution immersed in nanofiber reinforced prepreg, and BYK-066N surfactant into a planetary mixer, stir at 500 rpm for 15 min, then turn on vacuum defoaming for 10 min, and then add 4,4'-diaminodiphenylmethane, stir at low speed of 200 rpm for 5 min; Step 5, step curing molding: The material obtained in step 4 is subjected to pre-curing, main curing and post-curing molding three stages to obtain the high-toughness epoxy resin composition.

3. The method of producing a high-toughness epoxy resin composition according to claim 2, characterized by, The specific preparation method of the SiO2 / polythioether core-shell particles is as follows: Step 101, using tetraethyl orthosilicate as precursor, adding it into ethanol / water mixture, stirring at 400 rpm under 50.0℃±0.5℃ oil bath temperature control; slowly drop 5.0 mL of 25% ammonia water through constant pressure dropping funnel at a rate of 1 mL / min, continue to react for 6 h, after the reaction is completed, centrifuge the product, ultrasonic wash with ethanol for 3 times, 200 mL each time, ultrasonic frequency 40 kHz, 5 min, then vacuum dry at 60℃ for 12 h to obtain SiO2 nanoparticles with uniform particle size; Step 102, thiol modification: disperse SiO2 nanoparticles in toluene, add 3-mercaptopropyltrimethoxysilane, reflux at 80.0℃ under nitrogen protection for 12 h to realize surface thiol functionalization; Step 103, ATRP polymerization: adding mercapto-SiO2, allyl thioacetate and CuBr / PMDETA catalyst into the reaction system, purging with nitrogen at a flow rate of 20 mL / min for 30 min, then sealing, and performing surface-initiated atom transfer radical polymerization at 60.0℃ for 24 h, and obtaining core-shell structure SiO2 / polythioether particles after centrifugation, toluene washing and vacuum drying of the final product.

4. The method of producing a high-toughness epoxy resin composition according to claim 3, characterized by, The volume ratio of ethanol to deionized water in the ethanol / water mixture added in step 101 is 4:

1.

5. The method of producing a high toughness epoxy resin composition according to claim 2, characterized by, In step 101, the parameters for centrifugation of the product are as follows: centrifugation at a speed of 8000 rpm for 10 min.

6. The method of producing a high toughness epoxy resin composition according to claim 2, characterized by, The preparation method of the polyimide spinning solution is as follows: Polyimide powder is added to a dimethylacetamide / acetone mixed solvent, the mass ratio of dimethylacetamide to acetone in the mixed solvent is 7:3, and the obtained solution is filtered through a 200-mesh filter screen after constant temperature magnetic stirring at 50℃ for 6 hours to remove unsolved particles and impurities, thereby obtaining a polyimide spinning solution.

7. The method of producing a high toughness epoxy resin composition according to claim 6, characterized by, The preparation method of the nanofiber reinforced prepreg is as follows: A bipolar high-voltage power supply is used to drive the spinning process, the polyimide spinning solution is injected into a spinneret with an inner diameter of 0.51 mm at a flow rate of 1.0 mL / h, the spinneret is moved back and forth at a speed of 10 cm / s to uniformly deposit 5-15 layers of fibers on the surface of a bisphenol F type epoxy resin prepreg with a receiving distance of 15 cm, the thickness of a single layer of fibers is about 8 μm, and the deposited fibers are dried at 60℃ for 2 hours in vacuum to remove residual solvent.

8. The method of producing a high-toughness epoxy resin composition according to claim 7, characterized by, When preparing the nanofiber reinforced prepreg, each layer of fibers is deposited with an interval of 30 seconds to ensure that the resin prepreg fully infiltrates the fiber network.

9. The method of producing a high toughness epoxy resin composition according to claim 2, characterized by, In step 5, the specific parameters of the step curing molding stage are as follows: Pre-curing: temperature 80℃±0.5℃, heating rate 2℃ / min, holding time 2h±5min; Main curing: temperature 120℃±0.5℃, heating rate 3℃ / min, holding time 1h±3min; Post-curing: temperature 160℃±1.0℃, heating rate 5℃ / min, holding time 0.5h±2min, and completed under a vacuum degree of-0.08 MPa.

Images