High-performance epoxy resin and preparation method thereof

Abstract

The invention discloses high-performance epoxy resin and a preparation method thereof, and belongs to the technical field of high polymer materials, the high-performance epoxy resin is composed of epoxy resin, a curing agent and a modifier PSF-DOPO, and a DOPO structural unit in the modifier PSF-DOPO is chemically bonded on a main chain of polysulfone through a P-C bond. The method comprises the following steps: firstly, synthesizing a Schiff base monomer ESI; secondly, synthesizing novel polysulfone PSF; thirdly, dissolving DOPO (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) and PSF (Phosphorus Sulfonate Factor), and then reacting to obtain And finally, preparing the epoxy resin composite material. The material has high toughness and high strength and is prepared by physically blending the epoxy resin prepolymer and the modifier, the PSF-DOPO multifunctional polymer modifier is used for synchronous toughening and flame-retardant modification of epoxy resin, the mechanical property of the obtained material is comprehensively and remarkably improved, and the material also has excellent intrinsic flame retardance and is durable and stable in performance; the material has wide application prospects in the fields of aerospace structural members, high-end electronic packaging, high-performance composite materials and the like which require high mechanical properties and excellent flame retardance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a high-performance epoxy resin with high toughness, high strength and flame retardant properties and its preparation method. Background Technology

[0002] Epoxy resins are a class of thermosetting polymers characterized by epoxy groups. Their advantages stem from their unique molecular structure and cross-linking mechanism. Due to their excellent mechanical properties, chemical resistance, adhesive strength, and thermal stability, they are widely used in aerospace, electronic packaging, composite materials, and coatings. However, traditional epoxy resins, due to their highly cross-linked structure, suffer from inherent brittleness, poor impact resistance, and flammability, making them unsuitable for long-term use under dynamic loads or high-fire-risk environments.

[0003] With the increasing demand for lightweight and highly durable materials in industry, toughening modification of epoxy resins has become an important research direction in materials science. Existing toughening technologies mainly include the following: elastomer / rubber blends (such as carboxyl-terminated liquid nitrile butadiene rubber and amino-terminated liquid nitrile butadiene rubber): These absorb energy through crazing or shear yielding induced by the dispersed phase, but often lead to a significant decrease in modulus and heat resistance; thermoplastic modification (such as polyetherimide and polyethersulfone): These form a bicontinuous phase structure to improve toughness, but are limited by poor compatibility and a narrow processing window; nanoparticle filling (such as silica and carbon nanotubes): These utilize nano-effects to enhance interfacial interactions, but are prone to aggregation and have a threshold bottleneck in toughening efficiency; and topological design (such as hyperbranched polymers and core-shell particles): These improve toughness through molecular chain entanglement or energy dissipation mechanisms, but the synthesis process is complex and costly. Existing flame retardant technologies mainly include the following directions: halogenated flame retardants, which have good compatibility with polymer materials and can achieve excellent flame retardant effects with relatively small addition amounts. They achieve flame retardancy by decomposing to produce hydrogen halides, eliminating the active free radicals generated in the combustion reaction of polymer materials, thereby slowing down or terminating the chain reaction of combustion. However, they release harmful gases such as hydrogen halides during combustion. Phosphorus-based flame retardants achieve flame retardancy through a dual mechanism of gas phase and condensed phase. However, they have poor compatibility with epoxy resin matrices, and high addition amounts can reduce the mechanical properties of the material. These methods generally face the challenge of an inverted relationship between strength, toughness, and flame retardancy, and struggle to meet the requirements of process compatibility and cost for industrial production.

[0004] In conclusion, there is an urgent need to find a low-cost method for preparing high-performance epoxy resins. Summary of the Invention

[0005] To address the problems of insufficient toughness and flammability of epoxy resins in existing technologies, as well as the difficulty in simultaneously achieving toughening and flame retardant modification through traditional methods, which can easily lead to performance imbalances or migration and precipitation, this invention provides a high-performance epoxy resin and its preparation method. This invention designs and synthesizes a phosphorus-containing side-group functionalized modifier (phosphorus-containing polysulfone, PSF-DOPO) and introduces it into the epoxy resin system. This method organically combines the toughening advantages of PSF with the highly efficient flame retardant properties of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) through chemical bonding, achieving simultaneous reinforcement, toughening, and flame retardant modification of the epoxy resin. Furthermore, the modifier is chemically bound to the cross-linked network, avoiding the migration problem of small-molecule flame retardants and ensuring the long-term stability of the material's properties.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A high-performance epoxy resin is composed of epoxy resin, curing agent, and modifier PSF-DOPO. The DOPO structural units (flame-retardant functional groups) in the modifier PSF-DOPO are chemically bonded to the polysulfone backbone via PC bonds. The general structural formula of the modifier PSF-DOPO is as follows: Where n is an integer between 10 and 20.

[0007] A method for preparing a high-performance epoxy resin includes the following steps: Step 1: Synthesis of Schiff base monomer (ESI); Tyramine and vanillin were added to solvent A and reacted under mechanical stirring to obtain a yellow precipitate. After post-processing, including filtration, washing, and drying, a bright yellow powder product was obtained, which is the Schiff base monomer, denoted as ESI.

[0008] Furthermore, the molar ratio of tyramine to vanillin is 1:0.8 to 1.2, preferably 1:1.

[0009] Furthermore, solvent A is water, ethanol, or methanol, preferably water, and 20-30 mL of solvent A is added for every 0.01 mol of tyramine.

[0010] Furthermore, the reaction temperature is room temperature, and the time is 10-14 h, preferably 12 h.

[0011] Furthermore, the stirring speed is 400-600 rpm, and the mechanical stirring speed is preferably 500 rpm.

[0012] Furthermore, the post-processing specifically includes: The solid precipitate was collected by filtration using a Buchner funnel and washed with water at 70-90°C. The drying process consisted of two stages: pre-drying in a forced-air drying oven and then vacuum drying in a vacuum drying oven. The pre-drying temperature was 70-90°C for 10-14 hours; the vacuum drying temperature was 70-90°C for 10-14 hours.

[0013] Step 2: Synthesis of novel polysulfone (PSF); Step 2.1: In a three-necked flask equipped with a mechanical stirrer, thermometer, water separator and nitrogen inlet tube, solvent B is added to the flask under a nitrogen atmosphere.

[0014] Step 2.2: Add monomer ESI, 4,4′-dichlorodiphenyl sulfone (DCDPS), and anhydrous potassium carbonate (K2CO3) sequentially to the reaction flask, along with a dehydrating agent. Place the reaction system in an oil bath and, with mechanical stirring, gradually heat to 130℃~150℃. Reflux at this temperature for 1~2 h to complete dehydration and salt formation.

[0015] Step 2.3: After dehydration, raise the oil bath temperature to 170-190℃ to evaporate all the dehydrating agent. Then, stabilize the reaction temperature at 170-190℃ and continue the polymerization reaction for 5-7 hours. As the reaction proceeds, the system viscosity increases significantly. After the reaction is complete, cool the system to approximately 90-110℃, add preheated solvent B to reduce the viscosity of the reaction solution, and obtain a diluted solution.

[0016] Step 2.4: The diluted solution is slowly added dropwise to ethanol while stirring, and a yellow fibrous solid immediately precipitates. Post-processing, including filtration, washing, and drying, yields the yellow fibrous solid as PSF.

[0017] Furthermore, the solvent B is one of N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO), preferably NMP; 20 to 30 mL of solvent B is added for every 0.01 mol DCDPS.

[0018] Furthermore, the molar ratio of K2CO3 to 4,4′-dichlorodiphenyl sulfone (DCDPS) is 2 to 4:1, preferably 3:1.

[0019] Furthermore, the molar ratio of 4,4′-dichlorodiphenyl sulfone (DCDPS) to monomer ESI is 1:1.02 ~ 1.1.

[0020] Furthermore, the dehydrating agent is toluene or xylene, preferably toluene; 5 to 10 mL of dehydrating agent is added for every 0.01 mol DCDPS.

[0021] Furthermore, the stirring speed is 100-200 rpm, and the mechanical stirring speed is preferably 150 rpm.

[0022] Furthermore, the post-processing specifically includes: The product was washed three times with ethanol, and the solid precipitate was collected by filtration through a Buchner funnel. Subsequently, the crude product was transferred to a beaker containing an aqueous acetic acid solution and stirred for 1–2 hours to completely remove unreacted inorganic salts. After treatment, the product was filtered and washed with plenty of deionized water until the filtrate was neutral. The drying process consisted of two stages: pre-drying in a forced-air drying oven, followed by vacuum drying in a vacuum drying oven. The pre-drying temperature was 70–90°C for 10–14 hours; the vacuum drying temperature was 70–90°C for 10–14 hours, until a yellow fibrous solid was obtained, which was identified as PSF.

[0023] Step 3: Preparation of the modifier PSF-DOPO; DOPO and the synthesized PSF were added to solvent C and reacted under mechanical stirring for a certain period of time. After post-processing, including filtration, washing and drying, a pale yellow fibrous solid PSF-DOPO was obtained.

[0024] Furthermore, the molar ratio of PSF to DOPO is 1:0.5 to 1, preferably 1:0.75.

[0025] Furthermore, the solvent C is dimethylformamide, toluene, or chloroform, preferably chloroform; 20 to 30 mL of solvent C is added for every 0.01 mol PSF.

[0026] Furthermore, the reaction temperature is room temperature, and the time is 10 to 14 hours, preferably 12 hours.

[0027] Furthermore, the stirring speed is 400-600 rpm, and the mechanical stirring speed is preferably 500 rpm.

[0028] Furthermore, the post-processing specifically includes: The reaction solution was slowly added dropwise to ethanol under stirring, and a pale yellow fibrous solid immediately precipitated. The solid was filtered and washed three times with ethanol. The drying process consisted of two stages: pre-drying in a forced-air drying oven, followed by vacuum drying in a vacuum drying oven. The pre-drying temperature was 70–90°C for 10–14 h; the vacuum drying temperature was 70–90°C for 10–14 h, yielding a pale yellow fibrous solid, PSF-DOPO. The solid was analyzed by FT-IR and... 1 ¹H-NMR characterization confirmed that DOPO had been successfully grafted onto the PSF molecular chain.

[0029] Step 4: Preparation of epoxy resin composite material; Step 4.1: Add the modifier PSF-DOPO obtained in Step 3 to the viscous epoxy resin solution, and heat and stir at 60~80℃ to reduce its viscosity. Stir until the modifier PSF-DOPO is completely dissolved to form a homogeneous and transparent epoxy resin prepolymer solution. To promote dissolution, ultrasonic treatment can be used.

[0030] Step 4.2: Add curing agent to the epoxy resin prepolymer solution obtained in step 4.1, and stir at 60~80℃ for 10~20min until the curing agent is dissolved and the mixture is uniform to obtain a mixture.

[0031] Step 4.3: Place the mixture obtained in step 4.2 in a vacuum oven to remove residual air bubbles. Pour the mixture into a preheated mold and heat it at 60-70°C for 0.5-1.5 hours, at 110-130°C for 1-3 hours, and at 170-190°C for 1-3 hours.

[0032] Step 4.4: Slowly cool the mold to room temperature and remove the epoxy resin composite material.

[0033] Furthermore, the epoxy resin is epoxy resin E-51, epoxy resin E-44 or epoxy resin E-42, preferably epoxy resin E-51. Furthermore, the curing agent is m-phenylenediamine, 4,4′-diaminodiphenyl sulfone, or phthalic anhydride, preferably m-phenylenediamine; Furthermore, the mass ratio of epoxy resin to modifier is 100:0~5, preferably 100:2.5; Furthermore, the mass ratio of epoxy resin to curing agent is 100:10 to 15, preferably 100:13.

[0034] Effects and benefits of the present invention: (1) This invention prepares a high-performance epoxy resin composite material with both high toughness and high strength, which is prepared by physical blending of epoxy resin prepolymer and modifier. The modifier PSF-DOPO is innovatively synthesized. The modifier PSF-DOPO is formed by condensation polymerization and has a rigid main chain and DOPO flame-retardant side groups. The rigid main chain gives the modifier excellent strength and provides a certain strength and toughness to the epoxy resin. The DOPO side groups provide excellent flame-retardant properties to the epoxy resin. Moreover, the mutual compatibility between the modifier and the epoxy resin at the molecular level enhances the interfacial interaction between the modifier and the epoxy resin, which also ensures the strength and toughness of the composite material to a certain extent.

[0035] (2) This invention prepares a multifunctional polymer modifier with an innovative structure, PSF-DOPO, through a simple chemical reaction and applies it to the simultaneous toughening and flame-retardant modification of epoxy resin. The resulting material not only exhibits significantly improved mechanical properties (strength, modulus, and toughness) in all aspects, but also possesses excellent inherent flame retardancy and stable performance over time. This material has broad application prospects in aerospace structural components, high-end electronic packaging, and high-performance composite materials, which require high mechanical properties and excellent flame retardancy. Attached Figure Description

[0036] Figure 1 It is the modifier synthesized in Example 1. 1 H-NMR spectrum.

[0037] Figure 2 This is the FT-IR spectrum of the modifier synthesized in Example 2.

[0038] Figure 3 This is the GPC spectrum of the modifier synthesized in Example 3.

[0039] Figure 4 The following are impact strength and Young's modulus diagrams for comparative examples and three embodiments.

[0040] Figure 5 The following are diagrams showing the fracture toughness and critical strain energy release rate of the comparative example and three embodiments.

[0041] Figure 6 These are scanning electron microscope images of the impact fracture surface of epoxy resin composite material specimens; Figure 6 (a) is a scanning electron microscope image of the fracture surface of the control example in the impact experiment; Figure 6 (b) is a scanning electron microscope image of the fracture surface of the impact test in Example 1; Figure 6 (c) in the figure is a scanning electron microscope image of the fracture surface of the impact test in Example 2; Figure 6 (d) is a scanning electron microscope image of the fracture surface of the impact experiment in Example 3.

[0042] Figure 7 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0044] In the implementation of this invention, nuclear magnetic resonance hydrogen spectroscopy (NMR) is used. 1¹H-NMR was used to qualitatively and quantitatively analyze the chemical structure and functional group types of the modifier molecular chain. Fourier transform infrared spectroscopy (FT-IR) was used to further characterize the vibrational modes of characteristic functional groups in the modifier, thereby confirming its chemical composition and structural information. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution (PDI) of the modifier were determined by gel permeation chromatography (GPC) under specific mobile phase and standard conditions. The mechanical properties of the epoxy resin samples were tested using a universal testing machine. The cross-sections of the epoxy resin samples were observed and recorded using scanning electron microscopy (SEM).

[0045] Comparison Example Pour 50 g of epoxy resin E-51 into a separate beaker and stir at 70°C to reduce its viscosity. Then add 6.5 g of m-phenylenediamine (i.e., the mass ratio of epoxy resin to modifier PSF-DOPO is 100:0, and the mass ratio of epoxy resin to curing agent is 100:13), and stir at 70°C for 15 min until the curing agent is dissolved and the mixture is homogeneous. Place the mixture in a vacuum oven to remove residual air bubbles. Pour the mixture into a preheated mold and maintain it at 65°C for 1 h, 120°C for 2 h, and 180°C for 2 h. Finally, slowly cool the mold to room temperature and remove the epoxy resin composite material.

[0046] analyze: Figure 6 (a) is a scanning electron microscope image of the fracture surface of a pure epoxy resin specimen (i.e., this control example) in an impact test. The surface is smooth and the cracks are shallow, showing obvious brittle fracture, which reflects the low toughness of pure epoxy resin without the addition of modifiers.

[0047] Example 1 In a 100 mL three-necked flask equipped with a mechanical stirrer, 20 mL of ethanol was added, and 2.74 g of tyramine and 2.43 g of vanillin were accurately weighed (i.e., the molar ratio of tyramine to vanillin was 1:0.8). The mixture was reacted at 400 rpm for 10 h to obtain a yellow precipitate, namely ESI. After washing with water at 70 °C, the precipitate was pre-dried in a forced-air oven at 70 °C for 10 h, and then transferred to a vacuum oven at 70 °C for 10 h of vacuum drying.

[0048] In a three-necked flask equipped with a mechanical stirrer, thermometer, water separator, and nitrogen inlet tube, under a nitrogen atmosphere, 20 mL of DMSO and 5 mL of xylene were added. Accurately weighed 2.98 g of ESI, 2.87 g of 4,4′-dichlorodiphenyl sulfone, and 5.74 g of anhydrous K₂CO₃ (i.e., the molar ratio of ESI to 4,4′-dichlorodiphenyl sulfone is 1.1:1, and the mass ratio of K₂CO₃ to 4,4′-dichlorodiphenyl sulfone is 2:1). Under nitrogen protection and mechanical stirring at 100 rpm, the mixture was refluxed at 130 °C for 1 h to complete dehydration and salt formation. The toluene was then evaporated, and the water volume was recorded to ensure complete dehydration. The temperature was then increased and stabilized at 170 °C. The reaction was allowed to proceed for 5 h. After the system cooled to approximately 90 °C, preheated DMSO was added to reduce the viscosity of the reaction solution. The precipitate was dissolved in ethanol and neutralized with acetic acid. Unreacted monomers were removed by repeated ethanol washing, filtered, and then pre-dried in a 70°C forced-air oven for 10 h, before being transferred to a 70°C vacuum oven for 10 h of vacuum drying.

[0049] In a 100 mL three-necked flask equipped with a mechanical stirrer, 20 mL of dimethylformamide was added, and 5.03 g of PSF and 1.08 g of DOPO (i.e., the molar ratio of PSF to DOPO was 1:0.5) were accurately weighed. The mixture was reacted at 400 rpm for 10 h to obtain the modifier PSF-DOPO-1. After washing with water at 70 °C, the mixture was pre-dried in a forced-air oven at 70 °C for 10 h, and then transferred to a vacuum oven at 70 °C for 10 h of vacuum drying.

[0050] Take 1.25 g of the synthesized modifier PSF-DOPO-1 and 50 g of epoxy resin E-42 in a beaker (i.e., the mass ratio of epoxy resin to modifier PSF-DOPO is 100:2.5), and stir at 60°C for 10 min to reduce its viscosity. Stir until a homogeneous prepolymer solution is obtained. Then add 5 g of phthalic anhydride (i.e., the mass ratio of epoxy resin to curing agent is 100:10), and stir at 60°C for 10 min until the curing agent is dissolved and the mixture is homogeneous. Place the mixture in a vacuum oven to remove residual air bubbles. Pour the mixture into a preheated mold and maintain it at 60°C for 0.5 h, 110°C for 1 h, and 170°C for 1 h. Finally, slowly cool the mold to room temperature, remove the epoxy resin composite material, and name it EP-PSF-DOPO-1.

[0051] analyze: Figure 1 This is the modifier in this embodiment. 1The H-NMR spectra are shown in the figure: 8.30 ppm (m, 1H, Ar-CH-), 8.18 ~ 6.65 ppm (m, 15H, Ar-H), 3.83 ppm (m, 2H, -CH2-N), 3.74 ppm (m, 3H, -O-CH3), 2.95 ppm (m, 2H, Ar-CH2-).

[0052] analyze: Figure 4 The impact strength and Young's modulus of the epoxy resin samples containing this embodiment and the control example after unnotched impact test were observed to be significantly higher than those of the control example. This indicates that the toughness of the composite material was greatly improved, and the strength was not only not damaged but also greatly enhanced.

[0053] Example 2 In a 100 mL three-necked flask equipped with a mechanical stirrer, 30 mL of methanol was added, and 2.74 g of tyramine and 3.65 g of vanillin were accurately weighed (i.e., the molar ratio of tyramine to vanillin was 1:1.2). The mixture was reacted at 600 rpm for 14 h to obtain a yellow precipitate, namely ESI. After washing with water at 90 °C, the precipitate was pre-dried in a 90 °C forced-air oven for 14 h, and then transferred to a 90 °C vacuum oven for 14 h of vacuum drying.

[0054] In a three-necked flask equipped with a mechanical stirrer, thermometer, water separator, and nitrogen inlet tube, under a nitrogen atmosphere, 30 mL of NMP and 10 mL of toluene were added. Accurately weighed 2.84 g of ESI, 2.87 g of 4,4′-dichlorodiphenyl sulfone, and 11.48 g of anhydrous K₂CO₃ (i.e., the molar ratio of ESI to 4,4′-dichlorodiphenyl sulfone is 1.05:1, and the mass ratio of K₂CO₃ to 4,4′-dichlorodiphenyl sulfone is 4:1). Under nitrogen protection and mechanical stirring at 200 rpm, the mixture was refluxed at 150 °C for 2 h to complete dehydration and salt formation. The toluene was then evaporated, and the water volume was recorded to ensure complete dehydration. The temperature was then increased and stabilized at 190 °C. The reaction was allowed to proceed for 7 h. After the system cooled to approximately 110 °C, preheated NMP was added to reduce the viscosity of the reaction solution. The precipitate was dissolved in ethanol and neutralized with acetic acid. Unreacted monomers were removed by repeated washing with ethanol, filtered, and then pre-dried in a 90°C forced-air oven for 14 hours, before being transferred to a 90°C vacuum oven for 14 hours of vacuum drying.

[0055] In a 100 mL three-necked flask equipped with a mechanical stirrer, 30 mL of toluene was added, and 5.03 g of PSF and 2.16 g of DOPO (i.e., the molar ratio of PSF to DOPO was 1:1) were accurately weighed. The mixture was reacted at 600 rpm for 14 h to obtain the modifier PSF-DOPO-2. After washing with water at 70 °C, the mixture was pre-dried in a forced-air oven at 90 °C for 14 h, and then transferred to a vacuum oven at 90 °C for 14 h of vacuum drying.

[0056] 2.5 g of the synthesized modifier PSF-DOPO-2 and 50 g of epoxy resin E-44 were placed in a beaker (i.e., the mass ratio of epoxy resin to modifier PSF-DOPO was 100:5), and stirred at 80°C for 20 min to reduce its viscosity. The mixture was stirred until a homogeneous prepolymer solution was obtained. Then, 7.5 g of 4,4′-diaminodiphenyl sulfone (i.e., the mass ratio of epoxy resin to curing agent was 100:15) was added, and the mixture was stirred at 80°C for 20 min until the curing agent dissolved and the mixture was homogeneous. The mixture was placed in a vacuum oven to remove residual air bubbles. The mixture was poured into a preheated mold and kept at 70°C for 1.5 h, 130°C for 3 h, and 190°C for 3 h. Finally, the mold was slowly cooled to room temperature, and the epoxy resin composite material was removed and named EP-PSF-DOPO-2.

[0057] analyze: Figure 2 This is the FT-IR spectrum of the modifier in this embodiment. The FT-IR spectrum is at 3031 cm⁻¹. -1 and 2974 cm -1 Characteristic peaks are observed at 1490 cm⁻¹, corresponding to the stretching vibrations of aromatic and aliphatic CH₄, respectively. -1 The peak at 920 cm⁻¹ belongs to the aromatic C=C stretching vibration. -1 The appearance of a characteristic peak at this point indicates the successful introduction of the DOPO side group, which is a PC stretching vibration peak.

[0058] analyze: Figure 5 The fracture toughness and critical strain energy release rate of the epoxy resin samples containing this embodiment and the control example were calculated after unnotched impact test and bending test. It can be observed that the fracture toughness and critical strain energy release rate of the sample in this embodiment are significantly higher than those of the control example, which further proves the improvement of the toughness of the composite material.

[0059] Example 3 In a 100 mL three-necked flask equipped with a mechanical stirrer, 25 mL of water was added, and 2.74 g of tyramine and 3.04 g of vanillin were accurately weighed (i.e., the molar ratio of tyramine to vanillin was 1:1). The mixture was reacted at 500 rpm for 12 h to obtain a yellow precipitate, namely ESI. After washing with water at 80 °C, the precipitate was pre-dried in an 80 °C forced-air oven for 12 h, and then transferred to a vacuum oven at 80 °C for 12 h of vacuum drying.

[0060] In a three-necked flask equipped with a mechanical stirrer, thermometer, water separator, and nitrogen inlet tube, under a nitrogen atmosphere, 25 mL of NMP and 7.5 mL of toluene were added. Accurately weighed 2.76 g of ESI, 2.87 g of 4,4′-dichlorodiphenyl sulfone, and 8.61 g of anhydrous K₂CO₃ (i.e., the molar ratio of ESI to 4,4′-dichlorodiphenyl sulfone was 1.02:1, and the mass ratio of K₂CO₃ to 4,4′-dichlorodiphenyl sulfone was 3:1). Under nitrogen protection and mechanical stirring at 150 rpm, the mixture was heated to 140 °C and refluxed for 1.5 h to complete dehydration and salt formation. The toluene was then evaporated, and the water volume was recorded to ensure complete dehydration. The temperature was then increased and stabilized at 180 °C. The reaction was allowed to proceed for 6 h. After the system cooled to approximately 100 °C, preheated NMP was added to reduce the viscosity of the reaction solution. The precipitate was dissolved in ethanol and neutralized with acetic acid. Unreacted monomers were removed by repeated ethanol washing, filtered, and then pre-dried in a forced-air oven at 80°C for 12 hours, before being transferred to a vacuum oven at 80°C for 12 hours of vacuum drying.

[0061] In a 100 mL three-necked flask equipped with a mechanical stirrer, 25 mL of chloroform was added, and 5.03 g of PSF and 1.62 g of DOPO (i.e., the molar ratio of PSF to DOPO was 1:0.75) were accurately weighed. The mixture was reacted at 500 rpm for 12 h to obtain the modifier PSF-DOPO-3. After washing with water at 80 °C, the mixture was pre-dried in a forced-air oven at 80 °C for 12 h, and then transferred to a vacuum oven at 80 °C for 12 h of vacuum drying.

[0062] Take 1.25 g of the synthesized modifier PSF-DOPO-3 and 50 g of epoxy resin E-51 in a beaker (i.e., the mass ratio of epoxy resin to modifier PSF-DOPO is 100:2.5), and stir at 70°C for 15 min to reduce its viscosity. Stir until a homogeneous prepolymer solution is obtained. Then add 6.5 g of m-phenylenediamine (i.e., the mass ratio of epoxy resin to curing agent is 100:13), and stir at 70°C for 15 min until the curing agent is dissolved and mixed evenly. Place the mixture in a vacuum oven to remove residual air bubbles. Pour the mixture into a preheated mold and keep it at 65°C for 1 h, then at 180°C for 2 h, and then at 180°C for 2 h. Finally, slowly cool the mold to room temperature, remove the epoxy resin composite material, and name it EP-PSF-DOPO-3.

[0063] analyze: Figure 3 This is the GPC spectrum of the modifier in this embodiment. The GPC shows that Mw = 27072 g / mol, Mn = 13218 g / mol, and PDI = 2.05.

[0064] analyze: Figure 6 The epoxy resin samples from the three embodiments and the control example described above were subjected to an impact test using scanning electron microscopy. It can be observed that all sample surfaces are homogeneous and no phase separation occurred, indicating good compatibility between the modifier and the epoxy resin. Simultaneously, it is clearly observed that the fracture surface of the sample from the embodiments is very rough, exhibiting numerous wrinkles and shear bands. This indicates that the composite material undergoes plastic deformation under external impact. These wrinkles and shear bands absorb a large amount of energy, resist crack propagation, and improve the material's toughness.

[0065] analyze: Figure 7 The diagram shows the modification principle of the epoxy resin composite material corresponding to the three embodiments. The rigid main chain structure of the modifier is used to reinforce the epoxy resin, and the π-π interaction, hydrogen bonding and chain segment entanglement between the modifier and the epoxy resin matrix are used to toughen it.

[0066] Analysis: The impact strength, Young's modulus, fracture toughness, and critical strain energy release rate of the epoxy resin composite materials corresponding to the above control examples and three examples are shown in Table 1. The statistical results are shown in the following table: Table 1: Mechanical properties of epoxy resin composites

[0067] Impact strength reflects a material's impact resistance or its brittleness and toughness; Young's modulus is a physical quantity describing a solid material's resistance to deformation; fracture toughness characterizes a material's ability to prevent crack propagation and is a quantitative indicator of a material's toughness; critical energy release rate refers to the strain energy released per unit area of ​​crack propagation in a deformable object. The high-performance epoxy resins prepared in Examples 1-3 all exhibited good strength and toughness, showing a significant improvement compared to the pure epoxy resin in the control example.

[0068] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance epoxy resin, characterized in that, The preparation method includes the following steps: Step 1: Synthesize Schiff base monomer ESI; Tyramine and vanillin were added to solvent A and reacted under mechanical stirring to obtain a yellow precipitate. After post-processing, including filtration, washing and drying, a bright yellow powder product was obtained, which is the Schiff base monomer, denoted as ESI. Step 2: Synthesize a novel polysulfone PSF; Step 2.1: In a three-necked flask equipped with a mechanical stirrer, thermometer, water separator and nitrogen inlet tube, solvent B is added under a nitrogen atmosphere. Step 2.2: Add monomer ESI, 4,4′-dichlorodiphenyl sulfone (DCDPS), and anhydrous potassium carbonate (K2CO3) sequentially to the reaction flask, and add a dehydrating agent; place the reaction system in an oil bath, and under mechanical stirring, gradually raise the temperature to 130℃~150℃, and reflux for 1~2 h to complete the dehydration and salt formation; Step 2.3: After dehydration is complete, raise the temperature to 170-190℃ to evaporate all the dehydrating agent; then stabilize the reaction temperature at 170-190℃ and continue the polymerization reaction for 5-7 hours; as the reaction proceeds, the viscosity of the system increases; after the reaction is complete, cool the system to 90-110℃, add preheated solvent B to reduce the viscosity of the reaction solution, and obtain a diluted solution; Step 2.4: The diluted solution is added dropwise to ethanol with stirring, and a yellow fibrous solid immediately precipitates out; post-processing is performed, including filtration, washing, and drying, and the final yellow fibrous solid is PSF. Step 3: Prepare the modifier PSF-DOPO; DOPO and PSF obtained in step 2 were added to solvent C and reacted under mechanical stirring. Post-processing was carried out, including filtration, washing and drying, to finally obtain a light yellow fibrous solid PSF-DOPO. Step 4: Prepare epoxy resin composite material; Step 4.1: Add the modifier PSF-DOPO to the viscous epoxy resin solution and stir until the modifier PSF-DOPO is completely dissolved to form a uniform and transparent epoxy resin prepolymer solution. Step 4.2: Add curing agent to epoxy resin prepolymer solution, stir until curing agent is dissolved and mixed evenly to obtain mixture; Step 4.3: Pour the mixture into a preheated mold and keep it warm. Step 4.4: Slowly cool the mold to room temperature and remove the epoxy resin composite material.

2. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 1: The molar ratio of tyramine to vanillin is 1:0.8~1.

2. Solvent A is water, ethanol, or methanol; For every 0.01 mol of tyramine, add 20-30 mL of solvent A; The reaction was carried out at room temperature for 10–14 hours. The stirring speed is 400-600 rpm; The post-processing specifically involves: collecting the solid precipitate by filtration; washing with water at 70-90℃ and then drying to obtain ESI; the drying process is divided into two stages: first, pre-drying in a forced-air drying oven, and then transferring to a vacuum drying oven for vacuum drying; the pre-drying temperature is 70-90℃ and the time is 10-14 h; the vacuum drying temperature is 70-90℃ and the time is 10-14 h.

3. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 1: The molar ratio of tyramine to vanillin is 1:1; Solvent A is water.

4. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 2: The solvent B is one of N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO); 20-30 mL of solvent B is added for every 0.01 mol of DCDPS. The molar ratio of K2CO3 to 4,4′-dichlorodiphenyl sulfone (DCDPS) is 2 to 4:1; The molar ratio of 4,4′-dichlorodiphenyl sulfone (DCDPS) to the monomer ESI is 1:1.02 ~ 1.1; The dehydrating agent is toluene or xylene; 5 to 10 mL of dehydrating agent is added for every 0.01 mol DCDPS. The stirring speed is 100-200 rpm; The post-processing specifically involves: washing multiple times with ethanol, collecting the solid precipitate by filtration; transferring the crude product to a beaker containing an aqueous acetic acid solution and stirring for 1-2 hours to remove unreacted inorganic salts; filtering, washing with deionized water until the filtrate is neutral, and drying to obtain a yellow fibrous solid as PSF; the drying process is divided into two stages: pre-drying in a forced-air drying oven, and then transferring to a vacuum drying oven for vacuum drying; the pre-drying temperature is 70-90℃ and the time is 10-14 hours; the vacuum drying temperature is 70-90℃ and the time is 10-14 hours.

5. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 2: Solvent B is N-methylpyrrolidone (NMP). The molar ratio of K2CO3 to 4,4′-dichlorodiphenyl sulfone (DCDPS) is 3:1; The dehydrating agent is toluene.

6. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 3: The molar ratio of PSF to DOPO is 1:0.5 ~ 1. The solvent C is dimethylformamide, toluene, or chloroform; 20-30 mL of solvent C is added for every 0.01 mol PSF. The reaction temperature is room temperature, and the time is 10 to 14 hours. The stirring speed is 400-600 rpm; The post-treatment specifically involves: adding the reaction solution dropwise to ethanol under stirring, immediately precipitating a pale yellow fibrous solid; filtering, washing the solid multiple times with ethanol, and then drying to obtain the modifier PSF-DOPO; the drying process is divided into two stages: first, pre-drying in a forced-air drying oven, and then transferring to a vacuum drying oven for vacuum drying; the pre-drying temperature is 70~90℃, and the time is 10~14 h; the vacuum drying temperature is 70~90℃, and the time is 10~14 h.

7. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 3: The molar ratio of PSF to DOPO is 1:0.

75. The solvent C is trichloromethane.

8. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 4: In step 4.1, the mixture is stirred at 60~80℃ until the modifier PSF-DOPO is completely dissolved; the epoxy resin is epoxy resin E-51, epoxy resin E-44 or epoxy resin E-42; the mass ratio of epoxy resin to modifier is 100:0~5. In step 4.2, the curing agent is m-phenylenediamine, 4,4′-diaminodiphenyl sulfone, or phthalic anhydride; the mass ratio of epoxy resin to curing agent is 100:10~15; and the mixture is stirred at 60~80℃ for 10~20 minutes until the curing agent dissolves. In step 4.3, before pouring the mixture into the preheated mold, place it in a vacuum oven to remove residual air bubbles; The heat preservation process involves maintaining the temperature at 60-70℃ for 0.5-1.5 hours, at 110-130℃ for 1-3 hours, and at 170-190℃ for 1-3 hours.

9. The method for preparing a high-performance epoxy resin according to claim 1, characterized in that, In step 4: The epoxy resin is epoxy resin E-51; the mass ratio of the epoxy resin to the modifier is 100:2.

5. The curing agent is m-phenylenediamine; the mass ratio of epoxy resin to curing agent is 100:

13.

10. A high-performance epoxy resin, characterized in that, The product is prepared by any one of the preparation methods described in claims 1-9, and is composed of epoxy resin, curing agent, and modifier PSF-DOPO. The DOPO structural units in the modifier PSF-DOPO are chemically bonded to the main chain of polysulfone via PC bonds. The general structural formula of the modifier PSF-DOPO is as follows: Where n is an integer between 10 and 20.

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