High-toughness epoxy resin composition and preparation process thereof

Abstract

The invention discloses a high-toughness epoxy resin composition and a preparation process, and particularly relates to the field of modified epoxy resin, and the preparation process comprises the following steps: compounding 5-15 layers of electrostatic spinning nanofiber prepreg with an epoxy resin matrix containing dynamic covalent bonds (furan / bismaleimide), and adding 10-15 parts of SiO2 / polythioether core-shell particles; the viscosity of the resin is regulated and controlled to 800 mPa.s through pre-reaction, and fiber dispersion and interface strengthening are achieved in combination with a stepped curing process. According to the scheme, through the synergistic effect of nanofiber interlayer enhancement, dynamic bond energy dissipation and core-shell particle crack pinning, the impact strength and the bending strength are remarkably improved, meanwhile, the self-repairing potential is achieved, the process stability is high, the problems of fiber swelling, multi-phase interface degradation and internal stress accumulation in a traditional process are solved, and the method is suitable for industrial production. And the bottleneck of single performance and interface deterioration of the traditional toughening scheme is broken through.

Description

Technical Field

[0001] The present invention relates to the field of modified epoxy resins, and in particular to a high-toughness epoxy resin composition and a preparation process thereof. Background Art

[0002] Epoxy resins are widely used in aerospace, electronic packaging, composite materials, and other fields 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, limiting their application in dynamic load-bearing scenarios. To this end, the industry has conducted extensive research on "toughening modification," but existing technologies still face the following bottlenecks: 1. Limitations of a single toughening mechanism Elastomer toughening: Silver streaks are induced by adding rubber particles (such as CTBN) to dissipate energy, but this results in a significant decrease in material rigidity (tensile strength decreases by 30% to 50%), and the phase separation problem is prominent.

[0003] Nanoparticle filling: Nano-SiO2, carbon nanotubes, etc. are used to improve toughness, but high addition (>10wt%) can easily cause agglomeration and create stress concentration points.

[0004] Thermoplastic resin blends: such as PEI and PES can improve toughness, but the processing temperature is high (>300°C) and is incompatible with epoxy curing process.

[0005] 2. Trade-off between self-repair function and mechanical properties While the introduction of dynamic covalent bonds (such as Diels-Alder bonds and disulfide bonds) imparts self-healing capabilities to the material, the flexible segments reduce crosslink density, leading to a decrease in material strength. Furthermore, the self-healing efficiency of traditional dynamic networks relies on high temperatures and prolonged stimulation (e.g., 120°C / 2 hours), making it difficult to meet practical working conditions.

[0006] 3. Process compatibility and internal stress control problems In traditional toughening processes, the addition of nanomaterials significantly increases resin viscosity, limiting the uniform implantation of fiber reinforcements. Furthermore, the accumulation of thermal stress during the curing phase can easily cause microcracks, reducing the material's service life.

[0007] To address these challenges, the present invention proposes a multi-scale synergistically toughened epoxy resin system. This system utilizes a triple mechanism of nanofiber interlayer reinforcement, dynamic covalent bond energy dissipation, and core-shell particle crack pinning to overcome the technical limitations of single-scale toughening. Furthermore, through innovative electrospinning in-situ composite and step-curing processes, it addresses challenges such as poor nanomaterial dispersion, weak interfacial bonding, and internal stress accumulation, achieving a balance of high toughness, high strength, and self-healing capabilities, thus filling a gap in the existing technology. Summary of the Invention

[0008] The main purpose of the present invention is to provide a high-toughness epoxy resin composition and a preparation process, which can effectively solve the problems in the background technology.

[0009] To achieve the above object, the technical solution adopted by the present invention is: A high-toughness epoxy resin composition comprises the following components in parts by weight: Resin matrix: 100 parts of bisphenol F epoxy resin; Dynamic covalent network components: 10-20 parts of furan glycidyl ether and 3-8 parts of bismaleimide; Nanofiber reinforced prepreg: 5-15 layers of electrospun nanofiber; Reactive core-shell particles: 10-15 parts of SiO2 / polysulfide core-shell particles; Curing agent: 20-30 parts of 4,4'-diaminodiphenylmethane, 0.1-0.5 parts of triphenylphosphine; Coupling agent: 0.5-3 parts of γ-glycidyloxypropyltrimethoxysilane; Defoaming agent: BYK-066N surfactant 0.1-0.5 parts.

[0010] A process for preparing the above-mentioned high-toughness epoxy resin composition comprises the following specific steps: Step 1: Material preparation and pretreatment: Synthesize SiO2 / polysulfide core-shell particles, prepare polyimide spinning solution, and prepare nanofiber-reinforced prepreg; Step 2: Prepreg pretreatment: The nanofiber-reinforced prepreg was immersed in a 1 wt% γ-glycidyloxypropyltrimethoxysilane coupling agent ethanol solution for 5 minutes, and then dried at 80°C for 30 minutes to enhance the fiber-resin interface. Step 3, dynamic covalent network pre-reaction: 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. Step 4: Mixing and dispersing: Bisphenol F epoxy resin, pre-reacted furan glycidyl ether / bismaleimide system, SiO2 / polysulfide core-shell particles, γ-glycidyloxypropyltrimethoxysilane 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 minutes. Subsequently, vacuum degassing was started for 10 minutes, and then 4,4'-diaminodiphenylmethane was added and stirred at a low speed of 200 rpm for 5 minutes. Step 5: Step curing and 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 Preferably, the specific preparation method of the SiO2 / polythioether core-shell particle is as follows: Step 101, using tetraethyl orthosilicate as a precursor, adding it into an ethanol / water mixture, stirring at 400 rpm under the condition of 50.0℃±0.5℃ oil bath temperature control; slowly adding 5.0mL ammonia water (25% NH3) at a rate of 1mL / min through a constant pressure dropping funnel, continuously reacting for 6h, after the reaction is completed, centrifuging the product, sequentially washing it with ethanol for 3 times (200mL each time, ultrasonic frequency 40kHz, 5min), and then vacuum drying it at 60℃ for 12h to obtain SiO2 nanoparticles with uniform particle size; Step 102, thiol modification: dispersing the SiO2 nanoparticles in toluene, adding 3-mercaptopropyltrimethoxysilane, refluxing at 80.0℃ under nitrogen protection for 12h to realize surface thiol functionalization; Step 103, ATRP polymerization: adding the thiol-modified SiO2 and allyl thioacetate, CuBr / PMDETA catalyst into the reaction system, purging with nitrogen at a flow rate of 20mL / min for 30min, then sealing, and performing surface-initiated atom transfer radical polymerization at 60.0℃ for 24h, after which the final product is centrifuged, washed with toluene, and vacuum dried to obtain SiO2 / polythioether particles with core-shell structure.

[0011] Preferably, in step 101, the volume ratio of ethanol to deionized water in the ethanol / water mixture added is 4:1.

[0012] Preferably, in step 101, the parameters for centrifuging the product are as follows: centrifuging at a speed of 8000rpm for 10min.

[0013] Preferably, the preparation method of the polyimide spinning solution is as follows: Add polyimide powder into a dimethylacetamide / acetone mixed solvent (mass ratio 7:3), magnetically stir at 50℃ for 6 hours until completely dissolved, filter the obtained solution through a 200 mesh filter screen to remove unsolved particles and impurities, and obtain a polyimide spinning solution.

[0014] Preferably, the preparation method of the nanofiber reinforced prepreg is as follows: A bipolar high-voltage power supply was used to drive the spinning process. The polyimide spinning solution was injected into a spinneret with an inner diameter of 0.51 mm at a flow rate of 1.0 mL / h. A receiving distance of 15 cm was maintained on the surface of the bisphenol F epoxy resin prepreg. The spinneret was moved back and forth at a speed of 10 cm / s to uniformly deposit 5-15 layers of fibers. The thickness of a single fiber layer was about 8 μm. After total deposition, the fibers were vacuum dried at 60°C for 2 hours to remove solvent residues.

[0015] Preferably, when preparing the nanofiber reinforced prepreg, the deposition interval of each layer is 30 seconds to ensure that the resin prepreg fully impregnates the fiber network.

[0016] Preferably, in step 5, the specific parameters of the step curing molding stage are: 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 vacuum degree -0.08MPa.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes a triple mechanism of nanofiber interlayer reinforcement, dynamic covalent bond energy dissipation, and core-shell particle crack pinning to achieve excellent energy absorption under impact loads. The high modulus of the nanofibers effectively transmits stress, the reversible fracture of the dynamic bonds dissipates crack propagation energy, and the core-shell particles delay the fracture process through interfacial debonding and bridging. These three mechanisms synergistically significantly enhance the material's toughness and damage resistance, while avoiding the loss of rigidity caused by a single toughening mechanism, achieving a balanced optimization of high strength and high toughness.

[0018] 2. The design of the dynamic covalent network in this invention balances self-healing efficiency with matrix rigidity. The dynamic bonds rapidly reorganize under mild conditions (such as brief heating at 80°C), enabling efficient repair of damaged areas. The rigid main network remains stable during the repair process, avoiding the modulus loss associated with excessive flexible segments in traditional self-healing materials. Furthermore, the chemical synergy between the surface active groups of the core-shell particles and the dynamic bonds further enhances the bonding strength of the repair interface, ensuring stable mechanical properties after multiple repairs.

[0019] 3. The innovative pre-reaction-step-curing process of this invention resolves the conflict between high viscosity systems and nanofiber structure preservation. 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 microcracks by regulating dynamic bond reorganization and main network crosslinking in stages. The resulting material has minimal internal defects and a dense interface, meeting the requirements of high-precision molding.

[0020] 4. In this invention, the hydrogen bonding interactions between the nanofiber surface functional groups and the dynamic bonds, and the covalent coupling between the thiol 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 breakage and recombination of dynamic bonds, resulting in the material exhibiting excellent fatigue and impact resistance under complex loads. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0022] In the process of in-depth exploration of the collaborative design of epoxy resin toughening and functionalization, the inventors discovered through systematic literature research and test verification that although the existing technologies have achieved the development of single functional modules such as electrospinning nanofiber layer reinforcement, dynamic covalent bond self-healing network construction, and core-shell particle stress dissipation, their technical solutions are limited to single-dimensional performance optimization, and there are significant technical gaps and theoretical contradictions in the multi-factor synergistic mechanism, which are specifically manifested as follows: Existing research confirms that the morphological integrity of electrospun nanofibers is highly dependent on the low viscosity of the matrix resin (typically required to be <500 mPa·s). However, the introduction of dynamic covalent bonds (such as the Diels-Alder system) can increase the resin viscosity to 2000-3000 mPa·s, and the dispersion of core-shell particles further exacerbates the rheological degradation of the system. This contradiction causes the nanofibers to swell and collapse (fiber diameter deviation >50%) under traditional blending processes, resulting in a loss of reinforcement effect. Furthermore, the presence of flexible segments within the dynamic covalent network (e.g., furan-maleimide dynamic bonds with entanglement lengths of approximately 8-12 nm) significantly reduces the material's rigidity. However, the stress transfer efficiency of nanofibers and core-shell particles requires a highly rigid matrix. Existing technologies fail to address this rigid-tough balance paradox, resulting in the actual performance of the synergistic system falling short of the theoretical superposition value.

[0023] Therefore, the inventors provide a high-toughness epoxy resin composition that overcomes the above technical obstacles, which specifically includes the following components: Resin matrix: 100 parts of bisphenol F epoxy resin; Dynamic covalent network components: 10-20 parts of furan glycidyl ether, 3-8 parts of bismaleimide; Nanofiber reinforced prepreg: 5-15 layers of electrospun nanofiber; Reactive core-shell particles: 10-15 parts of SiO2 / polysulfide core-shell particles; Curing agent: 20-30 parts of 4,4'-diaminodiphenylmethane, 0.1-0.5 parts of triphenylphosphine; Coupling agent: 0.5-3 parts of γ-glycidyloxypropyltrimethoxysilane; Defoaming agent: BYK-066N surfactant 0.1-0.5 parts.

[0024] It should be noted that, in the present invention, SiO2 / polysulfide core-shell particles are prepared as follows: Step 101: Using tetraethyl orthosilicate as a precursor, add it to an ethanol / water mixture (volume ratio of 4:1, 200 mL of ethanol + 50 mL of deionized water), and stir at 400 rpm under the condition of oil bath temperature control at 50.0°C ± 0.5°C; slowly add 5.0 mL of ammonia water (25% NH3) at a rate of 1 mL / min through a constant pressure dropping funnel, and continue the reaction for 6 hours. After the reaction, centrifuge the product (8000 rpm × 10 min, centrifuge Sigma3-18KS, rotor number 12150), and ultrasonically wash it with ethanol three times (200 mL each time, ultrasonic frequency 40 kHz, 5 minutes), and then vacuum dry it at 60°C for 12 hours to obtain SiO2 nanoparticles with uniform particle size; Step 102, thiol modification: dispersing SiO2 nanoparticles in toluene, adding 3-mercaptopropyltrimethoxysilane, and reflux reaction at 80.0°C under nitrogen protection for 12 hours to achieve surface thiol functionalization; Step 103, ATRP polymerization: thiolated SiO2, allyl thioacetate, and CuBr / PMDETA catalyst are added to the reaction system, purged with nitrogen at a flow rate of 20 mL / min for 30 min, and then sealed. Surface-initiated atom transfer radical polymerization is carried out at 60.0°C for 24 h. The final product is centrifuged, washed with toluene, and vacuum-dried to obtain core-shell structured SiO2 / polysulfide particles.

[0025] Furthermore, the polyimide spinning solution is prepared as follows: Polyimide powder was added to a dimethylacetamide / acetone mixed solvent (mass ratio 7:3) and magnetically stirred at a constant temperature of 50°C for 6 hours until completely dissolved. The resulting solution was filtered through a 200-mesh filter to remove undissolved particles and impurities to obtain a polyimide spinning solution.

[0026] The specific method of preparing the nanofiber reinforced prepreg using the above-mentioned polyimide spinning solution is as follows: A bipolar high-voltage power supply was used to drive the spinning process. The polyimide spinning solution was injected into a spinneret with an inner diameter of 0.51 mm at a flow rate of 1.0 mL / h. A receiving distance of 15 cm was maintained on the surface of the bisphenol F epoxy resin prepreg. The spinneret was moved back and forth at a speed of 10 cm / s to uniformly deposit 5-15 layers of fibers. The thickness of a single fiber layer was about 8 μm. After total deposition, the fibers were vacuum dried at 60°C for 2 hours to remove solvent residues.

[0027] 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 infiltrates the fiber network.

[0028] The present invention is further disclosed below in conjunction with specific examples and comparative examples: Examples 1 to 5 are specific methods for preparing high-toughness epoxy resin compositions after adjusting other materials except for the use of 100 parts of bisphenol F epoxy resin; Comparative Example 1 is a method for preparing a high-toughness epoxy resin composition based on Example 1 without adding nanofiber reinforced prepreg; Comparative Example 2 is a method for preparing a high-toughness epoxy resin composition based on Example 1 without adding SiO2 / polysulfide core-shell particles; Comparative Example 3 is a method for preparing an epoxy resin composition based on Example 1 without adding a dynamic covalent network pre-reaction system.

[0029] Example 1 The raw materials used in this embodiment are as follows in parts by weight: Resin matrix: 100 parts of bisphenol F epoxy resin; Dynamic covalent network components: furan glycidyl ether 15 parts, bismaleimide 5 parts; Nanofiber reinforced prepreg: 8 layers of electrospun nanofiber; Reactive core-shell particles: 12 parts of SiO2 / polysulfide core-shell particles; Curing agent: 25 parts of 4,4'-diaminodiphenylmethane, 0.3 parts of triphenylphosphine; Coupling agent: 1.5 parts of γ-glycidyloxypropyltrimethoxysilane; Defoaming agent: 0.3 parts of BYK-066N surfactant.

[0030] Based on the above-mentioned raw materials, this embodiment prepares a high-toughness epoxy resin composition according to the following steps: Step 1: Material preparation and pretreatment: Synthesize SiO2 / polysulfide core-shell particles, prepare polyimide spinning solution, and prepare nanofiber-reinforced prepreg; Step 2: Prepreg pretreatment: The nanofiber-reinforced prepreg was immersed in a 1 wt% γ-glycidyloxypropyltrimethoxysilane coupling agent ethanol solution for 5 minutes, and then dried at 80°C for 30 minutes to enhance the fiber-resin interface. Step 3, dynamic covalent network pre-reaction: 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. Step 4: Mixing and dispersing: Bisphenol F epoxy resin, pre-reacted furan glycidyl ether / bismaleimide system, SiO2 / polysulfide core-shell particles, γ-glycidyloxypropyltrimethoxysilane 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 minutes. Subsequently, vacuum degassing was started for 10 minutes, and then 4,4'-diaminodiphenylmethane was added and stirred at a low speed of 200 rpm for 5 minutes. Step 5: Step curing and molding: The material obtained in step 4 is subjected to three stages of pre-curing, main curing and post-curing molding to obtain the high-toughness epoxy resin composition.

[0031] Among them, the specific parameters of the step curing molding stage are: 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 vacuum degree -0.08MPa.

[0032] Example 2 This example only adjusts the raw material ratios of each component on the basis of Example 1, and its preparation steps are exactly the same as those of the example, specifically as follows: Resin matrix: 100 parts of bisphenol F epoxy resin; Dynamic covalent network components: furan glycidyl ether 10 parts, bismaleimide 3 parts; Nanofiber reinforced prepreg: 5 layers of electrospun nanofiber; Reactive core-shell particles: 10 parts of SiO2 / polysulfide core-shell particles; Curing agent: 20 parts of 4,4'-diaminodiphenylmethane, 0.1 parts of triphenylphosphine; Coupling agent: 0.5 parts of γ-glycidyloxypropyltrimethoxysilane; Defoaming agent: BYK-066N surfactant 0.1 part.

[0033] Example 3 This example is based on example 1 only adjusting the ratio of raw materials of each component, its preparation steps and example are exactly the same, specifically: Resin matrix: bisphenol F type epoxy resin 100 parts; Dynamic covalent network component: furan glycidyl ether 20 parts, bismaleimide 8; Nanofiber reinforced prepreg: electrospun nanofiber layer 15 layers; Reactive core-shell particles: SiO2 / polythioether core-shell particles 15 parts; Curing agent: 4,4'-diaminodiphenylmethane 30 parts, triphenylphosphine 0.5 parts; Coupling agent: gamma-glycidyl ether oxypropyl trimethoxysilane 3 parts; Defoaming agent: BYK-066N surfactant 0.5 parts.

[0034] Example 4 This example is based on example 1 only adjusting the ratio of raw materials of each component, its preparation steps and example are exactly the same, specifically: Resin matrix: bisphenol F type epoxy resin 100 parts; Dynamic covalent network component: furan glycidyl ether 12 parts, bismaleimide 4; Nanofiber reinforced prepreg: electrospun nanofiber layer 8 layers; Reactive core-shell particles: SiO2 / polythioether core-shell particles 11 parts; Curing agent: 4,4'-diaminodiphenylmethane 22 parts, triphenylphosphine 0.25 parts; Coupling agent: gamma-glycidyl ether oxypropyl trimethoxysilane 1 part; Defoaming agent: BYK-066N surfactant 0.2 parts.

[0035] Example 5 This example is based on example 1 only adjusting the ratio of raw materials of each component, its preparation steps and example are exactly the same, specifically: Resin matrix: bisphenol F type epoxy resin 100 parts; Dynamic covalent network component: furan glycidyl ether 18 parts, bismaleimide 7; Nanofiber reinforced prepreg: electrospun nanofiber layer 13 layers; Reactive core-shell particles: SiO2 / polythioether core-shell particles 14 parts; Curing agent: 4,4'-diaminodiphenylmethane 27 parts, triphenylphosphine 0.4 parts; Coupling agent: γ-glycidoxypropyltrimethoxysilane 2 parts; Defoaming agent: BYK-066N surfactant 0.4 parts.

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is only that: In terms of raw material selection: no nano-fiber reinforced prepreg is added to prepare the high-toughness epoxy resin composition; In the preparation steps, the difference between this comparative example and Example 1 is that: in Step 1, no polyimide spinning solution and nano-fiber reinforced prepreg need to be prepared for pretreatment, Step 2 is deleted entirely, and in Step 4, no γ-glycidoxypropyltrimethoxysilane coupling agent ethanol solution for immersing the nano-fiber reinforced prepreg needs to be added during mixing and dispersion.

[0037] The rest of the materials and steps remain unchanged.

[0038] Comparative Example 2 The difference between this comparative example and Example 1 is only that: In terms of raw material selection: no SiO2 / polythioether core-shell particles are added; In the preparation steps: in Step 1, no SiO2 / polythioether core-shell particles need to be synthesized for pretreatment; and in Step 4, no SiO2 / polythioether core-shell particles need to be added during mixing and dispersion.

[0039] The rest of the materials and steps remain unchanged.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is only that: In terms of raw material selection: a dynamic covalent network pre-reaction system; In the preparation steps: Step 2 is deleted entirely; and in Step 4, no pre-reacted furan glycidyl ether / bismaleimide system needs to be added during mixing and dispersion.

[0041] The rest of the materials and steps remain unchanged.

[0042] Based on the above Examples 1-5 and Comparative Examples 1-3, the following performance tests are now conducted: I. Impact Toughness Test Impact strength is tested according to ASTM D6110 standard: Take the finished products prepared in Examples 1-5 and Comparative Examples 1-3 respectively, and mold them into V-shaped notched samples with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm (notch depth of 2 mm, radius of 0.25 mm). Ten parallel samples are prepared for each group, and the surface is polished to Ra≤0.8 μm. The test results are shown in Table 1.

[0043] Table 1: Impact toughness test results of Examples 1-5 and Comparative Examples 1-3 According to the results in Table 1, it can be seen that the samples prepared in Examples 1-5 have the highest impact strength, reaching (52.4-60.1 kJ / m²). In Comparative Example 1, no nanofiber-reinforced prepreg was added, and its impact strength dropped sharply. Although nanofiber-reinforced prepregs are present in Comparative Examples 2 and 3, SiO2 / polysulfide core-shell particles and dynamic covalent network pre-reaction systems are not added, and their impact strength is significantly reduced, but is better than that of Comparative Example 1. The reason is that the core-shell particles are toughened by crack deflection and bridging, while the reversible cross-linking after the dynamic covalent network breaks inhibits crack propagation and has a certain toughening effect. The synergy of the three makes Example 1 have the best overall performance.

[0044] 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 uniformity of the material and the performance of the samples is stable. However, the standard deviation of Comparative Example 1, ±3.2, shows that when nanofibers are not added, microcracks or interface defects are easily generated inside the material, resulting in large performance differences between samples.

[0045] 2. Dynamic Thermomechanical Analysis Sample preparation: Cut the cured plate into 35mm long × 10mm wide × 2mm thick samples and polish the surface Test equipment: TA Instruments Q800 DMA, three-point bending mode Test parameters: temperature range 30-250°C, heating rate 3°C / min, frequency 1 Hz, strain 0.05%.

[0046] Test standard: Refer to ASTM D4065; test results are shown in Table 2 Table 2. Dynamic thermomechanical analysis test results of Examples 1-5 and Comparative Examples 1-3 From the test results in Table 2, it can be seen that Examples 1-5 all have relatively high Tg and E' retention rates, while in Comparative Example 3, the Tg is only 142°C and the E' retention rate is 65.4%. It can be seen that insufficient crosslinking density leads to a sudden drop in high-temperature modulus. At the same time, the Tg in Example 3 was increased to 165°C, proving that increasing the dynamic network content can optimize thermal stability; Comparative Example 2 (no core-shell particles): the E' retention rate was 73.8%, proving that the core-shell particles inhibited molecular chain slip at high temperatures through interface strengthening.

[0047] 3. Three-point bending strength test Test standard: Refer to ASTMD790 Specimen preparation: Compression-molded standard specimens of 80 mm × 10 mm × 4 mm with a span of 64 mm.

[0048] Testing equipment: Instron 5969 universal testing machine, load cell 50 kN.

[0049] Test parameters: Loading rate 2 mm / min, record load-displacement curve until fracture. Test results are shown in Table 3.

[0050] Table 3: Three-point bending strength test results of Examples 1-5 and Comparative Examples 1-3 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 decreases significantly. This is because the core-shell particles (SiO2 / polysulfide) hinder crack propagation through the "pinning effect" and have a toughening effect. In Comparative Example 1, the flexural modulus is 2.78 GPa, indicating that fiber reinforcement increases the modulus by approximately 15.5%. In Comparative Example 3, the elongation at break is 3.5%, indicating that the dynamic network delays fracture through reversible bond reorganization.

[0051] From the above we can see that: The present invention introduces a dynamic covalent network pre-reaction (step 3 in the preparation process), pre-reacting furan glycidyl ether with bismaleimide for 30 minutes to reduce the resin viscosity from 2000 mPa·s to 800 mPa·s, which is compatible with the requirements of the electrospinning process (500-1000 mPa·s). The results of Test 1 show that the standard deviations of Examples 1-5 are all low. The pre-reaction system maintains low viscosity while ensuring the integrity of the fiber morphology and the reinforcement effect, overcoming the limitation of high viscosity leading to fiber failure in traditional processes. By regulating the ratio of rigid aromatic rings (bismaleimide) to flexible ether bonds (furan) in the dynamic network (3-8 parts), a rigid and flexible cross-linked network is formed. The bending modulus of Example 1 reaches 3.21 GPa (15% higher than that of the ordinary DA system), and the elongation at break is 5.7% (63% higher than that of Comparative Example 3), achieving the compatibility of the rigid matrix and flexible energy dissipation, filling the theoretical gap of "toughening at the expense of strength" in the dynamic network.

[0052] In addition, the present invention implements a coupling agent gradient treatment (steps 2+4), pre-treats the fiber with γ-glycidyl ether, and grafts sulfide bonds (-S-) on the surface of the core-shell particles to achieve chemical bonding (Si-OC). The interfacial chemical bonding inhibits phase separation, improves the synergistic dispersion efficiency of the core-shell particles and the fiber, and overcomes the industry problem of interface weakening of multi-component composite materials.

[0053] The present invention also designs a step-by-step curing process (step 5), which increases the temperature in stages (80°C pre-curing → 120°C main curing → 160°C post-curing), gradually releasing internal stress and further enhancing the toughness of the finished product.

[0054] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-toughness epoxy resin composition, characterized in that The composition comprises the following components in parts by weight: Resin matrix: 100 parts of bisphenol F epoxy resin; Dynamic covalent network components: 10-20 parts of furan glycidyl ether and 3-8 parts of bismaleimide; Nanofiber reinforced prepreg: 5-15 layers of electrospun nanofiber; Reactive core-shell particles: 10-15 parts of SiO2 / polysulfide core-shell particles; Curing agent: 20-30 parts of 4,4'-diaminodiphenylmethane, 0.1-0.5 parts of triphenylphosphine; Coupling agent: 0.5-3 parts of γ-glycidyloxypropyltrimethoxysilane; Defoaming agent: BYK-066N surfactant 0.1-0.5 parts.

2. A process for preparing the high-toughness epoxy resin composition according to claim 1, characterized in that: The specific steps are as follows: Step 1: Material preparation and pretreatment: Synthesize SiO2 / polysulfide core-shell particles, prepare polyimide spinning solution, and prepare nanofiber-reinforced prepreg; Step 2: Prepreg pretreatment: The nanofiber-reinforced prepreg was immersed in a 1 wt% ethanol solution of γ-glycidyloxypropyltrimethoxysilane coupling agent for 5 minutes, and then dried at 80°C for 30 minutes to enhance the fiber-resin interface. Step 3, dynamic covalent network pre-reaction: 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. Step 4: Mixing and dispersing: Bisphenol F epoxy resin, pre-reacted furan glycidyl ether / bismaleimide system, SiO2 / polysulfide core-shell particles, γ-glycidyloxypropyltrimethoxysilane 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 minutes. Subsequently, vacuum degassing was started for 10 minutes, and then 4,4'-diaminodiphenylmethane was added and stirred at a low speed of 200 rpm for 5 minutes. Step 5: Step curing and molding: The material obtained in step 4 is subjected to three stages of pre-curing, main curing and post-curing molding to obtain the high-toughness epoxy resin composition.

3. The process for preparing a high-toughness epoxy resin composition according to claim 2, wherein: The specific preparation method of the SiO2 / polysulfide core-shell particles is: Step 101: Using tetraethyl orthosilicate as a precursor, add it to an ethanol / water mixture, and stir at 400 rpm under the temperature control condition of an oil bath at 50.0°C ± 0.5°C; slowly add 5.0 mL of ammonia water (25% NH3) at a rate of 1 mL / min through a constant pressure dropping funnel, and continue the reaction for 6 hours. After the reaction is completed, the product is centrifuged and ultrasonically washed with ethanol three times (200 mL each time, ultrasonic frequency 40 kHz, 5 minutes), and then vacuum dried at 60°C for 12 hours to obtain SiO2 nanoparticles with uniform particle size; Step 102, thiol modification: dispersing SiO2 nanoparticles in toluene, adding 3-mercaptopropyltrimethoxysilane, and reflux reaction at 80.0°C under nitrogen protection for 12 hours to achieve surface thiol functionalization; Step 103, ATRP polymerization: thiolated SiO2, allyl thioacetate, and CuBr / PMDETA catalyst are added to the reaction system, purged with nitrogen at a flow rate of 20 mL / min for 30 min, and then sealed. Surface-initiated atom transfer radical polymerization is carried out at 60.0°C for 24 h. The final product is centrifuged, washed with toluene, and vacuum-dried to obtain core-shell structured SiO2 / polysulfide particles.

4. The process for preparing a high-toughness epoxy resin composition according to claim 3, wherein: In the ethanol / water mixture added in step 101, the volume ratio of ethanol to deionized water is 4:

1.

5. The process for preparing a high-toughness epoxy resin composition according to claim 2, wherein: In step 101, the parameters for centrifuging the product are specifically: centrifugation at a speed of 8000 rpm for 10 minutes.

6. The process for preparing a high-toughness epoxy resin composition according to claim 2, wherein: The polyimide spinning solution is prepared as follows: Polyimide powder was added to a dimethylacetamide / acetone mixed solvent (mass ratio 7:3) and magnetically stirred at a constant temperature of 50°C for 6 hours until completely dissolved. The resulting solution was filtered through a 200-mesh filter to remove undissolved particles and impurities to obtain a polyimide spinning solution.

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

8. The process for preparing a high-toughness epoxy resin composition according to claim 7, wherein: When preparing the nanofiber reinforced prepreg, the deposition interval of each layer is 30 seconds to ensure that the resin prepreg fully impregnates the fiber network.

9. The process for preparing a high-toughness epoxy resin composition according to claim 2, wherein: In step 5, the specific parameters of the step curing molding stage are: 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 vacuum degree -0.08MPa.

Images