Toughened epoxy resin and curing method thereof

Abstract

The invention discloses a toughened epoxy resin and a curing method thereof, and relates to the technical field of epoxy resins, the toughened epoxy resin comprises the following components: 100 parts of an epoxy resin matrix, specifically a mixture of bisphenol A epoxy resin and alicyclic epoxy resin, 5-35 parts of a composite amine curing agent, and 5-20 parts of a nano toughening agent, in particular to core-shell rubber particles grafted with epoxy groups on the surfaces, the core layer of each core-shell rubber particle is cross-linked polybutadiene, the shell layer of each core-shell rubber particle is polymethyl methacrylate, 0.5-3 parts of an accelerant comprising a bi-component synergistic accelerant, 1-5 parts of an interface enhancer, and a mixture of gamma-glycidyl ether oxypropyl trimethoxy silane and a titanate coupling agent, a bisphenol A type epoxy resin and a specific proportion of alicyclic epoxy resin are combined to construct an epoxy resin matrix according to a mass ratio of 2: 1, the epoxy resin matrix is matched with a composite amine curing agent prepared by carrying out a special three-step reaction on long-chain polyether diamine, aromatic diamine and anhydride, and key parameters such as molecular weight, functionality and molar ratio of the components are accurately regulated and controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and more specifically, to a toughened epoxy resin and a curing method thereof. Background Art

[0002] With the continuous improvement of the requirements for material properties in modern industry, epoxy resins have been widely used in the fields of aerospace, electronic packaging, automotive manufacturing, etc. due to their excellent mechanical properties, chemical corrosion resistance, and adhesiveness. However, traditional epoxy resins have the following technical bottlenecks during the curing process: Poor curing agent compatibility: When existing amine curing agents react with epoxy resins, the reaction rate is often too fast, resulting in intense local heat release, which is prone to generating internal stress and microcracks, affecting the mechanical properties and dimensional stability of the products. At the same time, it is difficult for the molecular structure of the curing agent to simultaneously take into account flexibility and rigidity, resulting in either high brittleness (such as pure aromatic amine curing systems) or insufficient heat resistance (such as aliphatic amine curing systems). Limited toughening effect: Traditional toughening agents such as microspheres and rubber particles are difficult to be uniformly dispersed in the epoxy matrix due to poor interfacial compatibility, and agglomeration often occurs. Moreover, the toughening mechanism mainly relies on physical encapsulation and cannot form effective chemical bonding, resulting in limited improvement in impact strength (usually only increasing by 20% - 30%), which is difficult to meet the requirement of impact strength ≥ 100 J / m for high-end applications. Rough curing process: Existing curing processes mostly use isothermal curing or simple stepwise temperature increase, which cannot accurately control the curing reaction path. This leads to insufficient early reactions (conversion rate < 30%) and excessive crosslinking in the later stage (generating crosslinking dead ends), and finally the porosity of the products is as high as 2% - 5%, seriously affecting the mechanical properties and medium resistance properties of the materials. Summary of the Invention

[0003] To solve the above problems, the present invention provides a toughened epoxy resin and a curing method thereof.

[0004] The present invention provides a toughened epoxy resin, and the toughened epoxy resin comprises the following components: 100 parts of an epoxy resin matrix, specifically a mixture of bisphenol A epoxy resin and alicyclic epoxy resin, with a mass ratio of 3:1; 5 to 35 parts of a composite amine curing agent, specifically formed by in-situ polycondensation reaction of long-chain polyether diamine and an aromatic amine modifier; 5 to 20 parts of a nano toughening agent, specifically core-shell rubber particles grafted with epoxy groups on the surface, with a core layer of crosslinked polybutadiene and a shell layer of polymethyl methacrylate; 0.5 to 3 parts of a promoter, comprising a two-component synergistic promoter, wherein the first component is 2-ethyl-4-methylimidazole, and the second component is boron trifluoride - monoethylamine complex, with a mass ratio of 1:0.2; 1 to 5 parts of an interface enhancer, which is a mixture of γ-glycidoxypropyltrimethoxysilane and a titanate coupling agent, with a mass ratio of 2:1.

[0005] Preferably, the specific curing method of the composite amine curing agent includes the following steps: Mix polyoxypropylene diamine and 4,4'-diaminodiphenylmethane in a molar ratio of 1:0.3, and then heat and stir to react to form a prepolymer with a rigid-flexible alternating structure; Slowly drop maleic anhydride into the prepolymer, control the molar ratio of the anhydride to the amino group in the prepolymer to be 1:1, heat and react at a constant temperature to form a modified amine with a carboxylic acid group at the end; Add bisphenol F type epoxy resin accounting for 5% to 8% of the total mass of the epoxy resin matrix, and carry out a chain extension reaction after heating to obtain a composite amine curing agent.

[0006] Preferably, the long-chain polyether diamine can be polyoxypropylene diamine, polytetrahydrofuran diamine or polyoxypropylene-tetrahydrofuran block copolymer diamine.

[0007] Preferably, the curing method of the nano toughening agent includes the following steps: First, synthesize a crosslinked polybutadiene core by emulsion polymerization method, the crosslinking agent is divinylbenzene, and the dosage is 1.5% to 2.5% of the mass of the butadiene monomer to complete the preparation of the core layer; Polymerize glycidyl methacrylate and methyl methacrylate on the surface of the core layer in a mass ratio of 1:2 to complete the grafting of the shell layer; React the shell layer particles with γ-glycidoxypropyltrimethoxysilane in an ethanol solution to complete the surface functionalization.

[0008] Preferably, the curing method of the auxiliary toughening agent is: Mix liquid carboxyl-terminated nitrile rubber and polyethersulfone in a mass ratio of 2:1, and melt and blend in a twin-screw extruder to obtain a blend product; After the blend product is pelletized, it is vacuum dried to obtain auxiliary toughening agent particles.

[0009] The present invention also proposes a curing method for a toughened epoxy resin, including the following steps: S1. Heat the epoxy resin matrix, add the interface enhancer and stir, then sequentially add the nano toughening agent, and use a high-shear emulsifier and an ultrasonic processor to disperse synergistically to obtain a mixture; S2. Preheat the composite amine curing agent and slowly add it to the mixture in S1, while stirring and maintaining vacuum degassing; Add a promoter, continue to stir and then inject into a mold, and pre-cure at a constant temperature; S3. Put the mixture after pre-curing in S2 into a curing furnace, heat it up to 105 to 115 °C at a rate of 0.8 to 1.2 °C / min, and keep it warm for 1.5 to 2 h; Continue to heat it up to 145 to 155 °C at a rate of 1.5 to 2.5 °C / min, and keep it warm for 3 to 4 h; Cool it down to below 80 °C at a rate of 0.5 to 1 °C / min and demold to obtain the final product.

[0010] Preferably, the addition amount of the composite amine curing agent is dynamically adjusted according to the real-time viscosity: When the initial viscosity of the system < 400 mPa·s, add 32 parts of the curing agent according to the upper limit of the formula; When the initial viscosity of the system ≥ 400 mPa·s and < 800 mPa·s, add 25 parts of the curing agent according to the median value of the formula; When the initial viscosity of the system ≥ 800 mPa·s, add 18 parts of the curing agent according to the lower limit of the formula; The viscosity is monitored by an on-line rotational viscometer.

[0011] Preferably, an alternating magnetic field needs to be applied synchronously during the S2 pre-curing stage, the magnetic field strength is 0.1 to 0.3 T, the frequency is 50 to 100 Hz, the magnetic field direction is parallel to the long axis direction of the mold, and the action time is 50% to 70% of the total pre-curing time.

[0012] Preferably, during the S3 high-temperature curing stage, a mixed gas containing 2% to 4% water vapor and 1% to 2% carbon dioxide is introduced into the curing furnace, the gas flow rate is 0.5 to 1.5 L / min, and the relative humidity is controlled at 40% to 60%.

[0013] Preferably, the specific steps of using a high-shear emulsifier and an ultrasonic processor to disperse synergistically in S1 are as follows: The synergistic action parameters of the high-shear emulsifier and the ultrasonic processor satisfy the following relational formula: ; where is the ultrasonic power density of the ultrasonic processor, with the unit of W / L, is the rotation speed of the high-shear emulsifier, in the range of 10,000 to 15,000 rpm, is the viscosity of the mixture before dispersion, with the unit of mPa·s, is the viscosity after dispersion, with the unit of mPa·s.

[0014] Beneficial effects; The epoxy resin matrix is constructed by combining bisphenol A type epoxy resin with an alicyclic epoxy resin in a specific ratio, and is paired with a composite amine curing agent prepared by a special three-step reaction of long-chain polyether diamine, aromatic diamine and anhydride. Each component is precisely regulated in key parameters such as molecular weight, functionality, and molar ratio. Under the synergistic action, the cured epoxy resin not only has a high-strength skeleton but also excellent flexibility. At the same time, a core-shell structured nano toughening agent is introduced. The core layer of cross-linked polybutadiene rubber in it provides an elastic basis. After the shell layer of glycidyl methacrylate grafted with epoxy groups is surface-functionalized, it is tightly bonded with the interface modifier to achieve stress dispersion toughening at the nanoscale; In the pre-dispersion and interface activation stage, precise temperature control and vacuum stirring are combined with high-shear and ultrasonic synergistic dispersion to ensure uniform mixing of components and activate the interface activity; in the low-temperature pre-curing stage, the curing agent is preheated and added evenly, and the dosage of the curing agent is dynamically regulated in cooperation with the viscosity monitored in real time, breaking the limitation of the traditional fixed ratio. At the same time, an alternating magnetic field is applied to induce the orientation arrangement of molecular chains, strengthening the interface bonding between the toughening agent and the matrix; in the gradient heating curing stage, the heating rate is planned to be slow first and then fast, combined with the regulation of the mixed gas environment during high-temperature curing, promoting the full reaction of anhydride and inhibiting the amine oxidation side reaction, to achieve the construction of a uniform and dense curing network. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] As Figure 1 shown: A toughened epoxy resin, the toughened epoxy resin comprising the following components: 100 parts of epoxy resin matrix, specifically a mixture of bisphenol A type epoxy resin and alicyclic epoxy resin, with a mass ratio of 3:1; It should be noted that the epoxy equivalent of bisphenol A type epoxy resin is 180 to 220 g / eq, and the epoxy equivalent of alicyclic epoxy resin is 120 to 160 g / eq; 5 to 35 parts of composite amine curing agent, specifically formed by in-situ polycondensation reaction of long-chain polyether diamine and aromatic amine modifier; it should be noted that the molecular weight of the long-chain polyether diamine is 2000 to 5000, and the terminal amine functionality is 2; 5 to 20 parts of nano toughening agent, specifically core-shell rubber particles grafted with epoxy groups on the surface, the core layer is cross-linked polybutadiene, and the shell layer is polymethyl methacrylate; it should be noted that the particle size is 80 to 300 nm, and the grafting rate is 5% to 15%; 0.5 to 3 parts of accelerator, including a two-component synergistic accelerator, wherein the first component is 2-ethyl-4-methylimidazole, and the second component is boron trifluoride-monoethylamine complex, with a mass ratio of 1:0.2; 1 to 5 parts of an interface enhancer, which is a mixture of γ-glycidoxypropyltrimethoxysilane and a titanate coupling agent, with a mass ratio of 2:1.

[0017] An epoxy resin matrix is composed of bisphenol A-type epoxy resin and alicyclic epoxy resin in a specific mass ratio; the composite amine curing agent is prepared through three-step reactions from long-chain polyether diamine, aromatic diamine, and anhydride, and strict limitations are imposed on parameters such as the molecular weight, functionality, and molar ratio of each substance; a core-shell structured nano toughening agent is used, and the specific substances and structural parameters of the core layer and the shell layer are clarified; there is also a promoter system, an interface modifier, and an auxiliary toughening agent with a specific composition, and the specific mass parts of each component are limited; Through the reasonable combination of each component and the control of specific parameters, the toughness of the epoxy resin is significantly improved while maintaining good mechanical properties. For example, the combination of bisphenol A-type epoxy resin and alicyclic epoxy resin takes into account the strength and flexibility of the material; the special preparation process and composition design of the composite amine curing agent can form a curing network with good crosslinking structure and flexibility; the core-shell structure and surface modification of the nano toughening agent can effectively disperse stress and improve the impact resistance of the material; the synergistic effect of the promoter system and the interface modifier accelerates the curing reaction rate and improves the interface bonding force; the auxiliary toughening agent further enhances the toughness of the material.

[0018] As an optional embodiment: The specific curing method of the composite amine curing agent includes the following steps: Mix long-chain polyether diamine and 4,4'-diaminodiphenylmethane in a molar ratio of 1:0.3, and then heat for stirring reaction to generate a prepolymer with a rigid-flexible alternating structure; it should be noted that in this embodiment, specifically under nitrogen protection, heat to 80 to 100 °C and stir for 2 to 4 h to generate a prepolymer with a rigid-flexible alternating structure; Slowly drop maleic anhydride into the prepolymer, control the molar ratio of the anhydride to the amino group in the prepolymer to be 1:1, heat and react at a constant temperature to generate a modified amine with carboxylic acid groups at the end; it should be noted that in this embodiment, react at 60 to 80 °C for 4 to 6 h to generate a modified amine with carboxylic acid groups at the end; Add bisphenol F-type epoxy resin accounting for 5% to 8% of the total mass of the epoxy resin matrix, and carry out a chain extension reaction after heating to obtain a composite amine curing agent. It should be noted that in this embodiment, the epoxy equivalent of bisphenol F-type epoxy resin is 160 to 180 g / eq, and the chain extension reaction after heating is specifically carried out at 125 to 135 °C for 1.5 to 2 h, and the viscosity of the final product is 2500 to 4500 mPa·s (25 °C); The preparation method of the polyamine curing agent is specified in detail, including the specific molar ratio, reaction temperature, stirring speed and time of long-chain polyether diamine and 4,4'-diaminodiphenylmethane in the pre-condensation reaction; the type of anhydride and the molar ratio with the amino group in the prepolymer, reaction temperature and time during anhydride capping; the dosage of bisphenol F-type epoxy resin and the chain extension reaction temperature and time during chain extension and crosslinking; The structure and properties of the curing agent are precisely controlled through step-by-step reactions. The pre-condensation reaction enables the long-chain polyether diamine and aromatic diamine to form a prepolymer with an alternating flexible-rigid structure, providing the basic structure for the curing network; anhydride capping introduces carboxylic acid groups, increasing the reaction activity and compatibility of the curing agent with epoxy resin; the chain extension and crosslinking reaction further increases the molecular weight and crosslinking density of the curing agent, making the final cured product have higher strength and toughness.

[0019] As an optional embodiment: The long-chain polyether diamine can be polyoxypropylene diamine, polytetrahydrofuran diamine or polyoxypropylene-polytetrahydrofuran block copolymer diamine. It should be noted that in this embodiment, polyoxypropylene diamine (D2000, molecular weight 2000±100, primary amine content ≥95%); Polytetrahydrofuran diamine (PTMG-2000, molecular weight 2000±200, tetrahydrofuran unit proportion ≥80%); Polyoxypropylene-polytetrahydrofuran block copolymer diamine (PPO-PTMG, molecular weight 3000±300, molar ratio of propylene oxide to tetrahydrofuran segments is (1:0.2) to (1:0.5)); The specific types of long-chain polyether diamines are defined, including polyoxypropylene diamine, polytetrahydrofuran diamine and polyoxypropylene-polytetrahydrofuran block copolymer diamine, and parameters such as their molecular weight, primary amine content, tetrahydrofuran unit proportion and molar ratio of propylene oxide to tetrahydrofuran segments are specified in detail; According to the characteristics of different types of long-chain polyether diamines, diverse sources of flexible segments are provided for the polyamine curing agent. These specific long-chain polyether diamines have good flexibility and reaction activity, and can cooperate with components such as aromatic diamines and anhydrides to form curing networks with different performance characteristics, so as to meet the requirements of epoxy resin toughness and other properties in different application scenarios.

[0020] As an optional embodiment: The curing method of the nano toughening agent includes the following steps: First, a crosslinked polybutadiene core is synthesized by emulsion polymerization. The crosslinking agent is divinylbenzene, and the dosage is 1.5% to 2.5% of the mass of the butadiene monomer to complete the preparation of the core layer. It should be noted that in this embodiment, the reaction temperature is 70 to 80°C and the crosslinking degree is 65% to 75%; Glycidyl methacrylate and methyl methacrylate were sequentially polymerized on the surface of the core layer at a mass ratio of 1:2 to complete the shell grafting. It should be noted that in this example, the initiator is potassium persulfate, the reaction temperature is 75 to 85 °C, and the shell thickness is controlled to be 15 to 30 nm by the monomer addition amount; The shell particles were reacted with γ-glycidoxypropyltrimethoxysilane in an ethanol solution to complete the surface functionalization. It should be noted that in this example, the amount of γ-glycidoxypropyltrimethoxysilane is 3% to 8% of the particle mass, the reaction temperature is 50 to 60 °C, the reaction time is 8 to 12 h, and the final epoxy group density on the particle surface is 0.8 to 1.5 mmol / g; The preparation method of the nano toughening agent was clarified, including the dosage of divinylbenzene as the crosslinking agent, the reaction temperature and the crosslinking degree in the core layer preparation; the mass ratio of GMA to MMA, the type of initiator, the reaction temperature and the control of the shell thickness during the shell grafting; the reaction conditions with KH560 and the final epoxy group density on the particle surface during the surface functionalization; By precisely controlling the preparation process of the nano toughening agent, its good toughening effect and compatibility are ensured. The crosslinked structure of the core layer provides a good elastic foundation. The specific thickness and composition design of the shell layer enable it to be evenly dispersed in the epoxy resin matrix and form chemical bonding with the interfacial modifier; the surface functionalization treatment further improves the compatibility and bonding force between the nano toughening agent and the epoxy resin matrix, thereby more effectively exerting the toughening effect, reducing stress concentration, and improving the toughness and mechanical properties of the material.

[0021] As an optional example: The curing method of the auxiliary toughening agent is as follows: Carboxyl-terminated liquid nitrile rubber and polyethersulfone were mixed at a mass ratio of 2:1 and melt-blended in a twin-screw extruder to obtain a blend product. It should be noted that in this example, the acrylonitrile content of the carboxyl-terminated liquid nitrile rubber is 18% to 26%, the molecular weight of the polyethersulfone is 30000 to 50000, melt-blended in a twin-screw extruder at 180 to 200 °C, the extrusion rate is 100 to 200 rpm, and the blending time is 5 to 8 min; After the blend product was pelletized, it was vacuum dried to obtain auxiliary toughening agent particles. It should be noted that in this example, it was vacuum dried at 80 to 100 °C for 6 to 8 h to obtain particles with a particle size of 0.5 to 2 mm; The carboxyl-terminated liquid nitrile rubber and polyethersulfone are effectively combined through a specific blending process, enabling the auxiliary toughening agent to be uniformly dispersed in the epoxy resin matrix and exert a synergistic toughening effect. The carboxyl-terminated liquid nitrile rubber provides good elasticity and toughness, while polyethersulfone improves the strength and heat resistance of the material. After blending under specific process conditions, they form an auxiliary toughening agent with a unique microstructure and properties, further improving the comprehensive performance of the epoxy resin.

[0022] As an optional embodiment: The present invention also provides a curing method for the toughened epoxy resin, which is applicable to the above-mentioned toughened epoxy resin and includes the following steps: S1. Heat the epoxy resin matrix, add the interfacial enhancer and stir, then sequentially add the nano-toughening agent, and use a high-shear emulsifier and an ultrasonic processor to disperse synergistically to obtain a mixture. It should be noted that in this embodiment, the specific steps are as follows: Heat the epoxy resin matrix to 55 to 65 °C, add the interfacial modifier, and stir at 300 to 500 rpm for 30 to 40 min under a vacuum of -0.08 to -0.1 MPa. Sequentially add the nano-toughening agent, and use a high-shear emulsifier (rotation speed 10000 to 15000 rpm) and an ultrasonic processor (frequency 25 to 35 kHz, power density 60 to 100 W / L) to disperse synergistically for 40 to 60 min, controlling the material temperature ≤ 75 °C. S2. Preheat the composite amine curing agent and slowly add it to the mixture in S1, while stirring and maintaining vacuum degassing. Add the accelerator, continue stirring and then inject into the mold for pre-curing at a constant temperature. It should be noted that in this embodiment, the specific steps are as follows: Preheat the composite amine curing agent to 45 to 55 °C and slowly add it to the mixture in step (2) at a rate of 5 to 10 g / min, while stirring at 400 to 600 rpm and maintaining vacuum degassing. Add the accelerator, continue stirring for 10 to 15 min and then inject into a mold preheated to 60 to 70 °C. Pre-cure at 65 to 75 °C for 1.5 to 2.5 h until the resin system conversion rate reaches 35% to 45% (determined by monitoring the change rate of the dielectric constant ≤ 0.5% / min through real-time dielectric analysis); S3. Put the pre-cured mixture in S2 into a curing furnace, heat it to 105 to 115 °C at a rate of 0.8 to 1.2 °C / min, and keep it warm for 1.5 to 2 h. Continue to heat it to 145 to 155 °C at a rate of 1.5 to 2.5 °C / min and keep it warm for 3 to 4 h. Cool down at a rate of 0.5 to 1 °C / min to below 80 °C and demold to obtain the final product.

[0023] By finely controlling the curing process in stages, ensure the smooth progress of the epoxy resin curing reaction and good molding. The pre-dispersion and interface activation stage makes each component fully mixed and uniform, improving the interface bonding force; the low-temperature pre-curing stage controls the conversion rate at the initial stage of the curing reaction to avoid defects caused by too fast reaction; the gradient heating curing stage makes the curing reaction proceed step by step at different temperatures to form a uniform and dense cured network structure, thereby improving the comprehensive performance and quality of the product. As an optional embodiment: the addition amount of the composite amine curing agent is dynamically adjusted according to the real-time viscosity: When the initial viscosity of the system < 400 mPa·s, add 32 parts of the curing agent according to the upper limit of the formula; When the initial viscosity of the system ≥ 400 mPa·s and < 800 mPa·s, add 25 parts of the curing agent according to the median value of the formula; When the initial viscosity of the system ≥ 800 mPa·s, add 18 parts of the curing agent according to the lower limit of the formula; The viscosity is monitored by an on-line rotational viscometer.

[0024] Avoid the problem of uneven local curing caused by the traditional way of adding a curing agent with a fixed ratio. By monitoring the viscosity in real time and adjusting the dosage of the curing agent accordingly, the curing reaction can proceed more uniformly and stably, ensuring a low porosity inside the product, improving the quality and performance consistency of the product, and reducing the defects and stress concentration points caused by uneven curing.

[0025] As an optional embodiment: an alternating magnetic field needs to be applied synchronously during the S2 pre-curing stage, the magnetic field strength is 0.1 to 0.3 T, the frequency is 50 to 100 Hz, the magnetic field direction is parallel to the long axis direction of the mold, and the action time is 50% to 70% of the total pre-curing time.

[0026] Use the alternating magnetic field to induce the orientation and arrangement of polyether diamine chain segments, enhance the interfacial bonding strength between the toughening agent and the matrix. Through the action of the magnetic field, the molecular chains are arranged orderly at the initial stage of curing to form a closer interfacial bonding, thereby effectively improving the impact strength of the material and improving its impact resistance performance. The impact strength is significantly improved through comparative experiments.

[0027] As an optional embodiment: during the S3 high-temperature curing stage, a mixed gas containing 2% to 4% water vapor and 1% to 2% carbon dioxide is introduced into the curing furnace, the gas flow rate is 0.5 to 1.5 L / min, and the relative humidity is controlled at 40% to 60%.

[0028] Water vapor is used to promote the hydrolysis of acid anhydride to form carboxylic acid, which participates in the curing reaction and improves the curing degree. At the same time, CO2 can inhibit the side reaction of amine oxidation, reducing the problems of incomplete curing and performance degradation caused by side reactions. By controlling the composition of the mixed gas and the environmental humidity, the curing reaction can proceed more fully and efficiently, improving the quality and performance of the cured product. DSC tests show that the curing degree can be increased to over 98%, and the residual heat enthalpy is low.

[0029] As an optional embodiment: The specific steps of using a high-shear emulsifier and an ultrasonic processor to disperse synergistically in S1 are as follows: The synergistic action parameters of the high-shear emulsifier and the ultrasonic processor satisfy the following relational formula: ; Where is the ultrasonic power density of the ultrasonic processor, with the unit of W / L, is the rotation speed of the high-shear emulsifier, ranging from 10,000 to 15,000 rpm, is the viscosity of the mixture before dispersion, with the unit of mPa·s, is the viscosity after dispersion, with the unit of mPa·s.

[0030] Ensure that the high-shear emulsifier and the ultrasonic processor can play the best synergistic role during the dispersion process, achieving efficient and uniform dispersion of components such as nano toughening agents and auxiliary toughening agents in the epoxy resin matrix. Through this formula relationship, the equipment parameters can be adjusted according to the actual process conditions, improving the dispersion efficiency and quality, avoiding material property differences caused by uneven dispersion, and ensuring the stability and reliability of the product performance.

[0031] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of this template.

Claims

1. A toughened epoxy resin, characterized in that, The described toughened epoxy resin comprises the following components: 100 parts of an epoxy resin matrix, specifically a mixture of bisphenol A epoxy resin and alicyclic epoxy resin, with a mass ratio of 3:1; 5 to 35 parts of a composite amine curing agent, specifically formed by in-situ polycondensation reaction of long-chain polyether diamine and aromatic amine modifier; 5 to 20 parts of a nano-toughening agent, specifically core-shell rubber particles with epoxy groups grafted on the surface, whose core layer is cross-linked polybutadiene and the shell layer is poly(methyl methacrylate); 0.5 to 3 parts of an accelerator, including a two-component synergistic accelerator, where the first component is 2-ethyl-4-methylimidazole and the second component is boron trifluoride-monoethylamine complex, with a mass ratio of 1:0.2; 1 to 5 parts of an interfacial enhancer, a mixture of γ-glycidoxypropyltrimethoxysilane and titanate coupling agent, with a mass ratio of 2:

1.

2. A toughened epoxy resin according to claim 1, wherein, The specific curing method of the composite amine curing agent includes the following steps: Mix long-chain polyether diamine and 4,4'-diaminodiphenylmethane in a molar ratio of 1:0.3, then heat and stir to react to form a prepolymer with a rigid-flexible alternating structure; Slowly drop maleic anhydride into the prepolymer, control the molar ratio of anhydride to amino groups in the prepolymer to be 1:1, heat and keep the temperature for reaction to form a modified amine with carboxylic acid groups at the end; Add bisphenol F epoxy resin accounting for 5% to 8% of the total mass of the epoxy resin matrix, and carry out a chain extension reaction after heating to obtain the composite amine curing agent.

3. The toughened epoxy resin according to claim 2, characterized in that, The long-chain polyether diamine can be polyoxypropylene diamine, polytetrahydrofuran diamine or polyoxypropylene-polytetrahydrofuran block copolymer diamine.

4. A toughened epoxy resin according to claim 1, wherein, The curing method of the nano-toughening agent includes the following steps: First, synthesize the cross-linked polybutadiene core by emulsion polymerization, with divinylbenzene as the cross-linking agent and the dosage being 1.5% to 2.5% of the mass of butadiene monomer, and complete the preparation of the core layer; Polymerize glycidyl methacrylate and methyl methacrylate on the surface of the core layer in turn, with a mass ratio of 1:2, and complete the grafting of the shell layer; React the shell layer particles with γ-glycidoxypropyltrimethoxysilane in an ethanol solution to complete surface functionalization.

5. A curing method for a toughened epoxy resin according to claim 1, characterized in that, The curing method of the auxiliary toughening agent is: Mix liquid carboxyl-terminated nitrile rubber and polyethersulfone in a mass ratio of 2:1, and melt-blend in a twin-screw extruder to obtain a blend product; After granulating the blend product, vacuum dry it to obtain auxiliary toughening agent particles.

6. A curing method for a toughened epoxy resin, applicable to the toughened epoxy resin described in any one of claims 1 to 5, characterized in that, It includes the following steps: S1. Heat the epoxy resin matrix, add the interfacial enhancer and stir, then add the nano-toughening agent in turn, and use a high-shear emulsifier and an ultrasonic processor to disperse synergistically to obtain a mixture; S2. Preheat the composite amine curing agent and slowly add it to the mixture in S1, while stirring and maintaining vacuum degassing; Add the accelerator, continue stirring and then inject it into a mold, and pre-cure at a constant temperature; S3. Put the pre-cured mixture in S2 into a curing furnace, heat it at a rate of 0.8 to 1.2 °C / min to 105 to 115 °C, and keep the temperature for 1.5 to 2 h; Continue to heat at a rate of 1.5 to 2.5 °C / min to 145 to 155 °C, and keep the temperature for 3 to 4 h; Cool down at a rate of 0.5 to 1 °C / min to below 80 °C and demold to obtain the final product.

7. A curing method for a toughened epoxy resin according to claim 6, characterized in that, The addition amount of the composite amine curing agent is dynamically adjusted according to the real-time viscosity: When the initial viscosity of the system < 400 mPa·s, add 32 parts of the curing agent according to the upper limit of the formula; When the initial viscosity of the system ≥ 400 mPa·s and < 800 mPa·s, add 25 parts of the curing agent according to the median value of the formula; When the initial viscosity of the system ≥ 800 mPa·s, add 18 parts of the curing agent according to the lower limit of the formula; The viscosity is monitored by an on-line rotational viscometer.

8. A curing method for a toughened epoxy resin according to claim 7, characterized in that, During the S2 pre-curing stage, an alternating magnetic field needs to be applied synchronously. The magnetic field strength is 0.1 to 0.3 T, the frequency is 50 to 100 Hz, the magnetic field direction is parallel to the long axis direction of the mold, and the action time is 50% to 70% of the total pre-curing time.

9. A curing method for a toughened epoxy resin according to claim 8, characterized in that, During the S3 high-temperature curing stage, a mixed gas containing 2% to 4% water vapor and 1% to 2% carbon dioxide is introduced into the curing furnace. The gas flow rate is 0.5 to 1.5 L / min, and the relative humidity is controlled at 40% to 60%.

10. The curing method of a toughened epoxy resin according to claim 6, characterized in that, The specific steps of the synergistic dispersion of the high-shear emulsifier and the ultrasonic processor in the S1 are as follows: The synergistic action parameters of the high-shear emulsifier and the ultrasonic processor satisfy the following relationship: ； wherein is the ultrasonic power density of the ultrasonic processor, with the unit of W / L, is the rotational speed of the high-shear emulsifier, with the range of 10,000 to 15,000 rpm, is the viscosity of the mixture before dispersion, with the unit of mPa·s, is the viscosity after dispersion, with the unit of mPa·s.

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