An epoxy resin for high-toughness, fast-curing prepreg, its preparation method and application

Abstract

This invention discloses a method for preparing a high-toughness, fast-curing epoxy resin for prepregs, comprising: using a stepwise premixing method to mix a matrix epoxy resin with a toughening agent to obtain a high-toughness epoxy resin; mixing the matrix epoxy resin, a latent epoxy resin curing agent, and an epoxy resin accelerator uniformly to obtain a paste-like latent curing system for fast-curing prepregs; mixing the high-toughness epoxy resin and the latent curing system for fast-curing prepregs and pouring the mixture into a mold, followed by vacuum curing to obtain the high-toughness, fast-curing epoxy resin for prepregs. This invention also discloses the epoxy resin obtained by the above method and its applications. The epoxy resin prepreg obtained by this invention has a long shelf life, which is beneficial for the large-scale, high-efficiency manufacturing of composite material components.

Description

Technical Field

[0001] This invention belongs to the field of structural composite material manufacturing technology, specifically relating to a method for preparing epoxy resin for high-toughness, fast-curing prepreg. Background Technology

[0002] Epoxy resins possess numerous advantages, including excellent mechanical properties, low shrinkage, and resistance to chemical corrosion. They are commonly used as matrix resins in composites with fibers / fabrics to prepare prepregs, which are widely used in the manufacture of advanced composite components for drones, aerospace, automobiles, and sporting goods. However, their brittleness after cross-linking and curing, poor impact resistance, and long curing time significantly limit their application in components requiring high toughness and large-scale mass production. A study (Acta Materiae Compositae Sinica, 2024, 41(4): 1830-1839) demonstrated that by synergistically toughening E-51 epoxy resin with block copolymers and nanoparticles, the critical stress intensity factor (KIC) of fracture toughness was increased by 145% compared to the pure E-51 epoxy resin system. However, complete curing still requires 80℃ / 4 h and 150℃ / 2 h, failing to simultaneously improve product toughness and molding efficiency. Chinese patent application (CN201811027230) discloses a rapid curing resin system and preparation method, which significantly shortens the curing cycle of epoxy resin and greatly improves molding efficiency. However, the impact strength of the cured casting is low, which limits its application in products with high requirements for the toughness of composite materials. Summary of the Invention

[0003] The purpose of this invention is to overcome the aforementioned defects and provide a high-toughness, fast-curing epoxy resin for prepregs, its preparation method, and its application, solving the technical problems of poor fracture toughness and long curing cycle of existing epoxy resins. The epoxy resin prepreg obtained by this invention has a long shelf life, which is beneficial for the large-scale, high-efficiency manufacturing of composite material components.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing a high-toughness, fast-curing epoxy resin for prepregs, comprising: (1) Mix the matrix epoxy resin with the toughening agent to obtain a high-toughness epoxy resin; (2) Mix the base epoxy resin, latent epoxy resin curing agent and epoxy resin accelerator evenly to obtain a paste-like latent curing system for fast-curing prepreg. (3) After mixing the high-toughness epoxy resin and the fast-curing prepreg with a latent curing system, pour the mixture into a mold and vacuum cure it to obtain the epoxy resin for the high-toughness fast-curing prepreg.

[0005] Furthermore, in step (1), the matrix epoxy resin includes one or more of bisphenol F type epoxy resin, bisphenol A type epoxy resin, glycidylamine type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin or linear aliphatic epoxy resin. The toughening agent includes one or more of the following: amino-terminated liquid nitrile rubber, polyarylether sulfone, phenolphthalein-based polyarylether ketone, nano-zirconia, multi-walled carbon nanotubes, biphenyl polyurethane liquid crystal, hyperbranched polyimide, or hyperbranched polyester.

[0006] Furthermore, in step (1), the mass ratio of the toughening agent to the matrix epoxy resin is 5-30:95-70.

[0007] Furthermore, in step (2), the latent epoxy resin curing agent includes one or more of the following: imidazole derivatives, dicyandiamide, liquefied dicyandiamide, boron trifluoride-amine complex, or aluminum trichloride-amine complex; Epoxy resin accelerators include one or more of the following: phenyl-substituted urea, alicyclic substituted urea, polyols, triethylamine, imidazole adducts, or amine adducts.

[0008] Furthermore, in step (2), the mass fractions of the matrix epoxy resin, the latent epoxy resin curing agent, and the epoxy resin accelerator are 20-60 parts, 10-50 parts, and 1-10 parts, respectively.

[0009] Furthermore, in step (3), the mass ratio of high-toughness epoxy resin to the latent curing system for rapid curing prepreg is 60-100:10-50.

[0010] Furthermore, in step (1), the base epoxy resin and the toughening agent are mixed at 100-140°C for 2-5 hours; In step (2), the base epoxy resin, latent epoxy resin curing agent and epoxy resin accelerator are mixed evenly at room temperature; In step (3), the high-toughness epoxy resin and the fast-curing prepreg are mixed at 50-80°C using a latent curing system; In step (3), the curing temperature is 100-140℃ and the curing time is 5-20min.

[0011] Furthermore, after obtaining the high-toughness epoxy resin in step (1), the high-toughness epoxy resin is stored at room temperature for later use; after obtaining the latent curing system for the fast-curing prepreg in step (2), the latent curing system for the fast-curing prepreg is stored at room temperature for later use; when it is necessary to prepare epoxy resin, the stored high-toughness epoxy resin and the latent curing system for the fast-curing prepreg are taken out and step (3) is performed.

[0012] An epoxy resin for high-toughness, fast-curing prepreg is obtained by the above-mentioned preparation method for an epoxy resin for high-toughness, fast-curing prepreg.

[0013] The application of the above-mentioned high-toughness, fast-curing epoxy resin for prepregs includes applying the above-mentioned high-toughness, fast-curing epoxy resin for prepregs to prepare fiber-reinforced epoxy resin prepregs or fiber-reinforced epoxy resin composites. Fiber-reinforced epoxy resin prepregs or fiber-reinforced epoxy resin composites are used to manufacture drones, aircraft composite components, automotive parts, or sporting goods components.

[0014] This invention designs and prepares a high-toughness, fast-curing epoxy resin system for prepregs, significantly improving the curing speed and toughness of the epoxy resin system. Based on a novel high-toughness, fast-curing epoxy resin, and combined with hot-melt process requirements and further optimization, this invention obtains a high-toughness, fast-curing epoxy resin formulation suitable for hot-melt prepreg processes. This invention uses a stepwise premixing method to separately prepare a high-toughness epoxy resin matrix mixed at high temperatures and a highly active latent curing system, avoiding explosive polymerization during resin preparation and solving the difficulties in the preparation process of fast-curing epoxy resin prepregs.

[0015] Compared with the prior art, the present invention has at least one of the following advantages: (1) The epoxy resin system prepared by adding toughening agent, latent curing agent and accelerator has high impact resistance and is completely cured at curing temperature of 100-140℃ and curing time of 5-20min, thereby improving the toughness and curing speed of epoxy resin. (2) This invention prepares the high-toughness epoxy resin matrix mixed at high temperature and the highly active latent curing system separately, avoiding the explosive polymerization during the resin preparation process, solving the difficulty of the preparation process of fast curing epoxy resin prepreg, and the prepreg has a long storage period, which is conducive to the mass and efficient manufacturing of composite material components. Detailed Implementation

[0016] The features and advantages of the present invention will become clearer and more explicit from the following detailed description.

[0017] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0018] This invention addresses the problems of poor fracture toughness and long curing cycles in existing epoxy resins by adding toughening agents to improve the toughness of the epoxy resin, using latent curing agents and epoxy resin accelerators to achieve rapid curing and a long shelf life, and leveraging the synergistic effect of these two agents to improve both the toughness and curing speed of the epoxy resin. This provides a method for preparing a prepreg epoxy resin that is both highly tough and can be cured rapidly. This invention can be applied to the preparation of high-toughness, rapidly curing prepreg epoxy resins. The preparation process is simple and suitable for industrial production, significantly shortening the molding cycle when used to manufacture products. It can be widely used in the high-efficiency mass production of aerospace load-bearing / non-load-bearing structural components.

[0019] This invention discloses a method for preparing a high-toughness, fast-curing epoxy resin for prepregs, comprising the following steps: (1) mixing a matrix epoxy resin and a toughening agent at 100-140°C for 2-5 hours to obtain a high-toughness epoxy resin, cooling it to room temperature for storage, wherein the mass ratio of the toughening agent to the matrix epoxy resin is 5-30:95-70; (2) stirring 20-60 parts of the matrix epoxy resin, 10-50 parts of a latent epoxy resin curing agent, and 1-10 parts of an epoxy resin accelerator at room temperature until homogeneous, obtaining a paste-like fast-curing epoxy resin. (3) The high-toughness epoxy resin matrix and the highly active latent curing system are prepared separately by stepwise premixing method, and then stirred evenly at a lower temperature (50-80℃). This can avoid the occurrence of explosive polymerization during the resin preparation process and effectively solve the problem of difficult preparation process of rapid curing epoxy resin system. The evenly mixed resin is poured into the casting sample mold, and the resin sample is cured after vacuuming in the oven for subsequent performance testing.

[0020] Preferably, in step (1), the matrix epoxy resin used can be one or more of the following: bisphenol F type epoxy resin, bisphenol A type epoxy resin, glycidylamine type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin, and linear aliphatic epoxy resin.

[0021] Preferably, in step (1), the toughening agent used can be one or more of the following: elastomer rubber, thermoplastic resin, nanoparticles, block copolymers, and hyperbranched copolymers. Specifically, it can be one or more of the following: amino-terminated liquid nitrile rubber, polyarylether sulfone, phenolphthalein-based polyarylether ketone, nano-zirconia, multi-walled carbon nanotubes, biphenyl polyurethane liquid crystal, hyperbranched polyimide, and hyperbranched polyester.

[0022] Preferably, in step (2), the latent epoxy resin curing agent used can be one or more of the following: imidazole derivatives, dicyandiamide, liquefied dicyandiamide, boron trifluoride-amine complex, and aluminum trichloride-amine complex.

[0023] Preferably, in step (2), the epoxy resin accelerator used can be one or more of the following: phenyl-substituted urea, alicyclic substituted urea, polyol, triethylamine, imidazole adduct, and amine adduct.

[0024] Preferably, in step (3), the high-toughness epoxy resin used is 60-100 parts by mass, and the latent curing system for the fast-curing prepreg is 10-50 parts by mass.

[0025] Preferably, in step (3), the curing temperature of the epoxy resin system used for the high-toughness fast-curing prepreg is 90-140℃, and the curing time is 5-20min.

[0026] Preferably, in step (3), the high-toughness, fast-curing prepreg resin system is used to prepare fiber-reinforced epoxy resin prepreg and composite materials for manufacturing drones, loitering munitions, aircraft composite components, automotive parts, and sporting goods components.

[0027] The epoxy resin system prepared by adding toughening agents, latent curing agents and accelerators has high impact resistance and complete curing at a curing temperature of 100-140℃ and a curing time of 5-20min, thereby improving the toughness and curing speed of epoxy resin.

[0028] This invention separates the high-toughness epoxy resin matrix, which is mixed at high temperature, from the highly active latent curing system, thus avoiding explosive polymerization during resin preparation. This solves the difficulties in the preparation process of fast-curing epoxy resin prepregs. At the same time, the prepregs have a long storage period, which is beneficial for the mass production and high-efficiency manufacturing of composite material components.

[0029] Example: A method for preparing a high-toughness, fast-curing epoxy resin for prepregs, comprising: (1) Mix the matrix epoxy resin and toughening agent at 100-140℃ for 2-5h to obtain a high-toughness epoxy resin, wherein the mass ratio of the toughening agent to the matrix epoxy resin is 5-30:95-70, and the sum of the mass ratios of the two is 100; (2) Stir 20-60 parts of matrix epoxy resin, 10-50 parts of latent epoxy resin curing agent and 1-10 parts of epoxy resin accelerator at room temperature to obtain a paste-like latent curing system for fast-curing prepreg; (3) Stir the high-toughness epoxy resin obtained in the above two steps and the latent curing system for fast-curing prepreg at 50-80℃, pour it into a casting sample mold, and cure it in an oven under vacuum to obtain a resin sample for subsequent performance testing.

[0030] In one specific embodiment, the matrix epoxy resin can be one or more of the following: bisphenol F type epoxy resin, bisphenol A type epoxy resin, glycidylamine type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin, and linear aliphatic epoxy resin.

[0031] In one specific embodiment, the toughening agent may be one or more of the following: amino-terminated liquid nitrile rubber, polyarylether sulfone, phenolphthalein-based polyarylether ketone, nano-zirconia, multi-walled carbon nanotubes, biphenyl polyurethane liquid crystal, hyperbranched polyimide, and hyperbranched polyester.

[0032] In one specific embodiment, the latent epoxy resin curing agent can be one or more of the following: imidazole derivatives, dicyandiamide, liquefied dicyandiamide, boron trifluoride-amine complex, and aluminum trichloride-amine complex.

[0033] In one specific embodiment, the epoxy resin accelerator can be one or more of the following: phenyl-substituted urea, alicyclic substituted urea, polyol, triethylamine, imidazole adduct, and amine adduct.

[0034] In one specific embodiment, the high-toughness epoxy resin comprises 60-100 parts by weight, and the latent curing system for the rapid-curing prepreg comprises 10-50 parts by weight.

[0035] In one specific embodiment, the curing temperature of the epoxy resin system for high-toughness fast-curing prepreg is 100-140℃, and the curing time is 5-20min.

[0036] The above-mentioned applications of epoxy resin for high-toughness rapid-curing prepregs include using the resin system for high-toughness rapid-curing prepregs to prepare fiber-reinforced epoxy resin prepregs and composite materials for manufacturing drones, aircraft composite components, automotive parts, and sporting goods components.

[0037] Example 1 This embodiment provides a method for preparing epoxy resin for high-toughness, fast-curing prepregs. The preparation method of the epoxy resin system is as follows: (1) Mix 30 parts of bisphenol F epoxy resin, 45 parts of glycidyl amine epoxy resin, 20 parts of toughening agent polyarylether sulfone and 5 parts of amino acrylate end-branched poly(amine-ester) at 140°C for 2 hours to obtain a high-toughness epoxy resin component, and cool to room temperature for storage.

[0038] (2) Mix 30 parts of bisphenol F epoxy resin, 10 parts of curing agent liquefied dicyandiamide, 3 parts of accelerator methylene diphenyl dimethylurea and 1 part of imidazole adduct at room temperature to obtain a paste-like latent curing component for fast-curing prepreg, and store at room temperature for later use.

[0039] The high-toughness epoxy resin component obtained in step (1) was baked in an oven for 2 hours, then cooled to 75°C and stirred with the latent curing component for the rapid-curing prepreg in step (2) for 15 minutes. The mass ratio of the high-toughness epoxy resin to the latent curing component for the rapid-curing prepreg was 100:44. After vacuum degassing, the high-toughness rapid-curing prepreg epoxy resin prepared in this invention was obtained. It was poured into a casting sample mold, vacuumed in an oven, and cured to obtain a resin sample for subsequent performance testing. The curing regime was 140°C / 5 minutes.

[0040] Example 2 This embodiment provides a method for preparing epoxy resin for high-toughness, fast-curing prepregs. The preparation method of the epoxy resin system is as follows: (1) Using nano-zirconia as a toughening agent, 30 parts of bisphenol F epoxy resin, 20 parts of bisphenol A epoxy resin, 40 parts of alicyclic epoxy resin and 10 parts of toughening agent were mixed at 120°C for 4 hours to obtain a high-toughness epoxy resin component, which was then cooled to room temperature for storage.

[0041] (2) Mix 25 parts of bisphenol A epoxy resin, 10 parts of curing agent 1-benzyl-2-methylimidazolium, 5 parts of boron trifluoride-amine complex, 2 parts of accelerator alicyclic substituted urea and 1 part of triethylamine at room temperature to obtain a paste-like fast-curing prepreg latent curing component, and store at room temperature for later use.

[0042] (3) The high-toughness epoxy resin component obtained in step (1) is baked in an oven for 2 hours, cooled to 70°C, and stirred with the latent curing component for the rapid-curing prepreg in step (2) for 20 minutes. The mass ratio of the high-toughness epoxy resin to the latent curing component for the rapid-curing prepreg is 100:43. After vacuum degassing, the high-toughness rapid-curing prepreg epoxy resin prepared in this invention is obtained. It is poured into a casting sample mold, vacuumed in an oven, and cured to obtain a resin sample for subsequent performance testing. The curing regime is 120°C / 10 minutes.

[0043] Example 3 This embodiment provides a method for preparing epoxy resin for high-toughness, fast-curing prepregs. The preparation method of the epoxy resin system is as follows: (1) 20 parts of linear aliphatic epoxy resin, 20 parts of phenolic epoxy resin, 40 parts of alicyclic epoxy resin, 19.5 parts of toughening agent terminal amino liquid nitrile rubber and 0.5 parts of multi-walled carbon nanotubes were mixed at 100°C for 3 hours to obtain a high-toughness epoxy resin component, which was then cooled to room temperature and stored.

[0044] (2) Mix 20 parts of alicyclic epoxy resin, 5 parts of curing agent dicyandiamide, 5 parts of aluminum trichloride-amine complex, 2 parts of accelerator polyol and 3 parts of imidazole adduct at room temperature to obtain a paste-like fast-curing prepreg latent curing component, and store at room temperature for later use.

[0045] (3) The high-toughness epoxy resin component obtained in step (1) is baked in an oven for 2 hours, cooled to 80°C, and stirred with the latent curing component for the rapid-curing prepreg in step (2) for 15 minutes. The mass ratio of the high-toughness epoxy resin to the latent curing component for the rapid-curing prepreg is 100:35. After vacuum degassing, the high-toughness rapid-curing prepreg epoxy resin prepared in this invention is obtained. It is poured into a casting sample mold, vacuumed in an oven, and cured to obtain a resin sample. Subsequent performance tests are performed, and the curing regime is 110°C / 20 minutes.

[0046] Comparative Example This comparative example provides a method for preparing an epoxy resin, and the method for preparing the epoxy resin system is as follows: 100 parts of bisphenol A epoxy resin and 6 parts of dicyandiamide curing agent were stirred at high speed at 90°C for 30 minutes. After vacuum degassing, the epoxy resin was discharged to obtain the prepared epoxy resin. The resin was poured into a casting mold, vacuum-cured in an oven to obtain resin samples, which were then subjected to subsequent energy testing.

[0047] The curing regime is 100℃ / 1h + 130℃ / 4h.

[0048] The specific performance data of Examples 1-3 and comparative examples are shown in Table 1.

[0049] Table 1 Performance data of the examples and comparative examples

[0050] As shown in Table 1, compared with conventional epoxy resins, the high-toughness, fast-curing epoxy resin prepared by this invention exhibits a 29.0%-38.7% increase in impact strength and excellent toughness. Furthermore, the high-toughness, fast-curing epoxy resin prepared using the method provided by this invention demonstrates excellent process performance, meeting the process requirements for prepreg production.

[0051] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0052] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing epoxy resin for high-toughness, fast-curing prepregs, characterized in that, include: (1) Mix the matrix epoxy resin with the toughening agent to obtain a high-toughness epoxy resin; (2) Mix the base epoxy resin, latent epoxy resin curing agent and epoxy resin accelerator evenly to obtain a paste-like latent curing system for fast-curing prepreg. (3) After mixing the high-toughness epoxy resin and the fast-curing prepreg with a latent curing system, pour the mixture into a mold and vacuum cure it to obtain the epoxy resin for the high-toughness fast-curing prepreg.

2. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 1, characterized in that, In step (1), the matrix epoxy resin includes one or more of bisphenol F type epoxy resin, bisphenol A type epoxy resin, glycidylamine type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin or linear aliphatic epoxy resin. The toughening agent includes one or more of the following: amino-terminated liquid nitrile rubber, polyarylether sulfone, phenolphthalein-based polyarylether ketone, nano-zirconia, multi-walled carbon nanotubes, biphenyl polyurethane liquid crystal, hyperbranched polyimide, or hyperbranched polyester.

3. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 1, characterized in that, In step (1), the mass ratio of toughening agent to matrix epoxy resin is 5-30:95-70.

4. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 1, characterized in that, In step (2), the latent epoxy resin curing agent includes one or more of the following: imidazole derivatives, dicyandiamide, liquefied dicyandiamide, boron trifluoride-amine complex, or aluminum trichloride-amine complex; Epoxy resin accelerators include one or more of the following: phenyl-substituted urea, alicyclic substituted urea, polyols, triethylamine, imidazole adducts, or amine adducts.

5. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 3, characterized in that, In step (2), the mass fractions of the matrix epoxy resin, the latent epoxy resin curing agent, and the epoxy resin accelerator are 20-60 parts, 10-50 parts, and 1-10 parts, respectively.

6. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 1, characterized in that, In step (3), the mass ratio of high-toughness epoxy resin to latent curing system for fast-curing prepreg is 60-100:10-50.

7. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 1, characterized in that, In step (1), the base epoxy resin and toughening agent are mixed at 100-140℃ for 2-5 hours; In step (2), the base epoxy resin, latent epoxy resin curing agent and epoxy resin accelerator are mixed evenly at room temperature; In step (3), the high-toughness epoxy resin and the fast-curing prepreg are mixed at 50-80°C using a latent curing system; In step (3), the curing temperature is 100-140℃ and the curing time is 5-20min.

8. The method for preparing a high-toughness, fast-curing epoxy resin for prepregs according to claim 1, characterized in that, After obtaining the high-toughness epoxy resin in step (1), the high-toughness epoxy resin is stored at room temperature for later use; after obtaining the latent curing system for the fast-curing prepreg in step (2), the latent curing system for the fast-curing prepreg is stored at room temperature for later use. When it is necessary to prepare epoxy resin, the stored high-toughness epoxy resin and fast-curing prepreg are taken out using a latent curing system and proceeded to step (3).

9. An epoxy resin for high-toughness, fast-curing prepregs, characterized in that, The epoxy resin for high-toughness, rapid-curing prepreg is obtained by the preparation method of any one of claims 1-8.

10. An application of an epoxy resin for high-toughness, fast-curing prepregs, characterized in that, The epoxy resin for high-toughness, fast-curing prepreg as described in claim 9 is used to prepare fiber-reinforced epoxy resin prepregs or fiber-reinforced epoxy resin composites. Fiber-reinforced epoxy resin prepregs or fiber-reinforced epoxy resin composites are used to manufacture drones, aircraft composite components, automotive parts, or sporting goods components.

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