Epoxy resin matrix and its preparation method, prepreg and composite materials

Abstract

This invention relates to epoxy resin matrices and their preparation methods, prepregs, and composite materials, belonging to the field of polymer materials technology. The epoxy resin matrix comprises, by weight, the following components: epoxy resin: 100 parts; cyano-containing polyethersulfone: 5-20 parts; carboxyl-terminated nitrile butadiene rubber: 5-20 parts. This invention introduces cyano-containing polyethersulfone and carboxyl-terminated nitrile butadiene rubber as composite toughening agents, resulting in a synergistic effect. The cyano groups in the cyano-containing polyethersulfone enhance the fiber-resin interface bonding, and its high-rigidity skeleton increases the matrix modulus; the carboxyl-terminated nitrile butadiene rubber forms a rubber phase in the matrix, absorbing energy through cavitation. The resulting composite material maintains high heat resistance (Tg≥120℃) while exhibiting a 0° tensile strength exceeding 2800 MPa and an interlaminar shear strength exceeding 88 MPa, demonstrating excellent comprehensive mechanical properties and suitability for high-end fields such as aerospace and new energy vehicles.

Description

Technical Field

[0001] This invention relates to epoxy resin matrices and their preparation methods, prepregs and composite materials, belonging to the field of polymer materials technology. Background Technology

[0002] In the field of composite materials, carbon fiber reinforced epoxy resin unidirectional tapes have become a core material for achieving structural lightweighting in aerospace, new energy vehicles, high-end industrial equipment, and sporting goods due to their superior specific strength and specific stiffness. As applications expand to high-dynamic fatigue, high-impact environments, and harsh thermal load conditions, higher demands are being placed on the comprehensive mechanical properties of composite materials. The market not only pursues lightweighting but also requires materials to maintain high heat resistance while simultaneously improving tensile strength in the fiber direction (determining the upper limit of load-bearing capacity in the main load-bearing direction) and interlaminar shear strength to resist delamination (ensuring structural integrity and preventing delamination failure). However, in existing technologies, it is often difficult to simultaneously achieve both 0° tensile strength and interlaminar shear strength, and toughening modification often comes at the cost of sacrificing the glass transition temperature (Tg).

[0003] To improve the toughness of composite materials, the industry commonly uses toughening agents to add toughening agents to epoxy resins. Among these, carboxyl-terminated nitrile butadiene rubber (CTBN) is a widely used reactive toughening agent. It can form micron-sized rubber particles in the matrix, effectively absorbing energy through cavitation and shear yielding mechanisms, significantly improving the fracture toughness of the material. However, the introduction of CTBN significantly reduces the Tg of the epoxy resin matrix, impairing the high-temperature performance of the material and making it difficult to apply in fields with specific heat resistance requirements, such as aerospace and new energy vehicle battery pack casings.

[0004] Chinese patent application CN121086465A discloses a hot-melt epoxy resin composition that uses a mixture of carboxyl-terminated nitrile butadiene rubber and polyethersulfone as a toughening agent. While toughening, this composition effectively maintains the tackiness of the resin matrix during curing, preventing severe resin flow and improving the peel strength of the composite material. However, it does not solve the problem of simultaneously achieving high toughness and high heat resistance. The final composite material's 0° tensile strength and interlaminar shear strength still need improvement, making it difficult to meet the design requirements for extreme lightweighting and higher damage tolerance. Summary of the Invention

[0005] The first objective of this invention is to provide an epoxy resin matrix.

[0006] To achieve the first objective of the present invention, the epoxy resin matrix comprises, by weight, the following components: epoxy resin: 100 parts; cyano-containing polyethersulfone: 5 to 20 parts; carboxyl-terminated nitrile rubber: 5 to 20 parts.

[0007] In one specific embodiment, the cyano-containing polyether sulfone has a weight-average molecular weight of 10,000 to 60,000 and a number-average molecular weight of 5,000 to 55,000; preferably, the cyano-containing polyether sulfone content is 8 to 20 parts.

[0008] In one specific embodiment, the number average molecular weight of the carboxyl-terminated butadiene-acrylonitrile rubber is 2500-5000, and the mass fraction of acrylonitrile is 5-30%.

[0009] In one specific embodiment, the structure of the cyano-containing polyethersulfone toughening agent is shown in Formula I:

[0010]

[0011] Formula I.

[0012] In one specific embodiment, the epoxy resin matrix further comprises, by weight: curing agent: 2-100 parts; accelerator: 0.5-3 parts; filler: 0-30 parts; solvent: 0-200 parts.

[0013] In one specific embodiment, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and glycidylamine type epoxy resin.

[0014] In one specific embodiment, the curing agent is selected from at least one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, dicyandiamide, 4,4'-diaminodiphenylmethane, and boron trifluoride monoethylamine.

[0015] In one specific embodiment, the promoter is selected from at least one of 2-methylimidazole, 4-methylimidazole, benzyldimethylamine, N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea), and 2-ethyl-4-methylimidazole.

[0016] In one specific embodiment, the filler is selected from at least one of talc, titanium dioxide, silicon dioxide, aluminum hydroxide, and aluminum oxide.

[0017] In one specific embodiment, the solvent is selected from at least one of dimethylformamide, acetone, butanone, toluene, xylene, propylene glycol methyl ether, ethylene glycol methyl ether, and cyclohexanone.

[0018] A second objective of this invention is to provide a method for preparing the above-mentioned epoxy resin matrix.

[0019] To achieve the second objective of the present invention, the method includes the following steps:

[0020] A. A mixture containing cyano polyethersulfone and carboxyl-terminated butadiene-acrylonitrile rubber is mixed with epoxy resin and solvent at 40-150°C to obtain mixture A;

[0021] B. Cool the mixture A to 40-70℃, add the filler, mix thoroughly to obtain mixture B;

[0022] C. Add curing agent to mixture B at 40-70℃ and mix evenly to obtain mixture C;

[0023] D. Under conditions of 40–70°C, an accelerator is added to mixture C, the mixture is mixed evenly, and the mixture is degassed under vacuum to obtain the epoxy resin matrix;

[0024] The preferred steps for uniform mixing include stirring at 800–1500 RPM for 30–60 minutes; for uniform mixing in step B, it includes stirring at 800–1500 RPM for 20–120 minutes; and for uniform mixing in steps C and D, it includes stirring at 800–1500 RPM for 20–40 minutes.

[0025] A third objective of this invention is to provide a prepreg.

[0026] To achieve a third objective of the present invention, the prepreg comprises reinforcing fibers and the aforementioned epoxy resin matrix, wherein the epoxy resin matrix is ​​impregnated on the reinforcing fibers.

[0027] In one specific embodiment, the reinforcing fiber is carbon fiber, preferably T700 grade carbon fiber.

[0028] The fourth object of the present invention is to provide a fiber-reinforced composite material.

[0029] To achieve the fourth objective of the present invention, the fiber-reinforced composite material is obtained by curing and molding the above-mentioned prepreg.

[0030] In one specific embodiment, the fiber-reinforced composite material has a 0° tensile strength of ≥2800 MPa, a glass transition temperature Tg maintained at 120–140°C, and an interlaminar shear strength of ≥88 MPa.

[0031] The curing pressure for the curing process is 0.4–0.7 MPa, the vacuum degree is ≤-0.095 MPa, the curing temperature is 120–190°C, and the curing time is 30–120 minutes.

[0032] Beneficial effects

[0033] 1. Significantly improved mechanical properties: Through the synergistic toughening of "cyano-containing polyethersulfone" and "carboxyl-terminated nitrile rubber", the T700 carbon fiber composite material prepared by the epoxy resin matrix of the present invention can achieve a tensile strength of over 2800 MPa at 0° and an interlaminar shear strength of over 88 MPa, which is far superior to the existing technology.

[0034] 2. Maintaining excellent heat resistance: The high Tg cyano-containing polyethersulfone forms a rigid skeleton after curing, which effectively compensates for the reduction of matrix Tg by the carboxyl-terminated nitrile rubber, so that the glass transition temperature of the composite material is stably maintained between 120 and 140℃ after curing, which meets the heat resistance requirements of high-end applications.

[0035] 3. Clear synergistic mechanism: The strongly polar cyano (-CN) groups in cyano-containing polyethersulfone can form a strong interaction with the carbon fiber surface, enhancing interfacial bonding; simultaneously, its high modulus properties improve the matrix stiffness. The carboxyl-terminated nitrile rubber forms a rubber phase in the matrix, absorbing energy through the cavitation effect. The synergistic effect of these two components achieves a balance of high strength, high toughness, and high heat resistance. Detailed Implementation

[0036] To achieve the first objective of the present invention, the epoxy resin matrix comprises, by weight, the following components: epoxy resin: 100 parts; cyano-containing polyethersulfone: 5 to 20 parts; carboxyl-terminated nitrile rubber: 5 to 20 parts.

[0037] In one specific embodiment, the cyano-containing polyether sulfone has a weight-average molecular weight of 10,000 to 60,000 and a number-average molecular weight of 5,000 to 55,000; preferably, the cyano-containing polyether sulfone content is 8 to 20 parts.

[0038] In one specific embodiment, the number average molecular weight of the carboxyl-terminated butadiene-acrylonitrile rubber is 2500-5000, and the mass fraction of acrylonitrile is 5-30%.

[0039] In one specific embodiment, the structure of the cyano-containing polyethersulfone toughening agent is shown in Formula I:

[0040]

[0041] Formula I.

[0042] In one specific embodiment, the epoxy resin matrix further comprises, by weight: curing agent: 2-100 parts; accelerator: 0.5-3 parts; filler: 0-30 parts; solvent: 0-200 parts.

[0043] In one specific embodiment, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and glycidylamine type epoxy resin.

[0044] In one specific embodiment, the curing agent is selected from at least one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, dicyandiamide, 4,4'-diaminodiphenylmethane, and boron trifluoride monoethylamine.

[0045] In one specific embodiment, the promoter is selected from at least one of 2-methylimidazole, 4-methylimidazole, benzyldimethylamine, N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea), and 2-ethyl-4-methylimidazole.

[0046] In one specific embodiment, the filler is selected from at least one of talc, titanium dioxide, silicon dioxide, aluminum hydroxide, and aluminum oxide.

[0047] In one specific embodiment, the solvent is selected from at least one of dimethylformamide, acetone, butanone, toluene, xylene, propylene glycol methyl ether, ethylene glycol methyl ether, and cyclohexanone.

[0048] To achieve the second objective of the present invention, the method includes the following steps:

[0049] A. A mixture containing cyano polyethersulfone and carboxyl-terminated butadiene-acrylonitrile rubber is mixed with epoxy resin and solvent at 40-150°C to obtain mixture A;

[0050] B. Cool the mixture A to 40-70℃, add the filler, mix thoroughly to obtain mixture B;

[0051] C. Add curing agent to mixture B at 40-70℃ and mix evenly to obtain mixture C;

[0052] D. Under conditions of 40–70°C, an accelerator is added to mixture C, the mixture is mixed evenly, and the mixture is degassed under vacuum to obtain the epoxy resin matrix;

[0053] The preferred steps for uniform mixing include stirring at 800–1500 RPM for 30–60 minutes; for uniform mixing in step B, it includes stirring at 800–1500 RPM for 20–120 minutes; and for uniform mixing in steps C and D, it includes stirring at 800–1500 RPM for 20–40 minutes.

[0054] Preparation of epoxy resin matrix

[0055] First, the cyano-containing polyethersulfone toughening agent and carboxyl-terminated butadiene-acrylonitrile rubber are added to the main resin and solvent (if present) at 120°C and mixed in a stirred tank at a dispersion speed of 800-1500 RPM for 30-60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0056] Subsequently, the system temperature was lowered to 40–70°C, the filler was added, and the mixture was stirred at a dispersion speed of 800–1500 RPM for 20–120 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0057] Next, add the curing agent at 40–70°C and stir at a dispersion speed of 800–1500 RPM for 20–40 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0058] Finally, add the accelerator at 40–70°C and stir at a dispersion speed of 800–1500 RPM for 20–40 minutes to ensure that the accelerator is uniformly dispersed in the system.

[0059] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0060] To achieve a third objective of the present invention, the prepreg comprises reinforcing fibers and the aforementioned epoxy resin matrix, wherein the epoxy resin matrix is ​​impregnated on the reinforcing fibers.

[0061] In one specific embodiment, the reinforcing fiber is carbon fiber.

[0062] Prepreg preparation

[0063] Solvent-free method for epoxy resin matrix

[0064] First, the epoxy resin matrix is ​​formed into a film using a film-forming machine: the epoxy resin matrix is ​​transported to the coating head by a metering pump and uniformly coated onto the release paper at 50-100°C. The film thickness is controlled by a doctor blade or roller coating method. After cooling and shaping by a cooling roller, the film is wound up to obtain an epoxy resin film with uniform thickness.

[0065] Then, T700S carbon fiber is used as the reinforcing material. After unwinding using a yarn unwinding frame, the fiber is evenly spread. The above-mentioned adhesive film and fiber are then laminated in a laminating device: typically, a double-film method is used to hold the fiber, with one film on the top and bottom layers and a uniformly spread carbon fiber bundle in the middle. The laminate is heated and pressurized by heated rollers (80-180℃) to melt the adhesive film and fully impregnate the fiber. The laminated prepreg is cooled and shaped by cooling rollers and then wound by a release paper winding device to obtain a dry prepreg with uniform width and no defects.

[0066] Solvent-containing epoxy resin matrix manufacturing process

[0067] The epoxy resin matrix is ​​transferred to the adhesive bath of the prepreg production line, and the adhesive temperature is maintained at 50–80°C. T700S carbon fiber is used as the reinforcing material and is introduced into the adhesive bath via guide rollers to ensure uniform impregnation of the fiber with the adhesive. After impregnation, the fiber is passed through extrusion rollers to control the resin content. Subsequently, it is heated in stages within a temperature range of 80–190°C to remove solvent from the adhesive and achieve pre-curing (B-stage curing). Finally, it is cooled by cooling rollers, laminated with release paper, and wound by a winding device to obtain a prepreg with uniform width and no defects.

[0068] To achieve the fourth objective of the present invention, the fiber-reinforced composite material is obtained by curing and molding the above-mentioned prepreg.

[0069] In one specific embodiment, the fiber-reinforced composite material has a 0° tensile strength of ≥2800 MPa, a glass transition temperature Tg maintained at 120–140°C, and an interlaminar shear strength of ≥88 MPa.

[0070] The curing pressure for the curing process is 0.4–0.7 MPa, the curing temperature is 120–190°C, and the curing time is 30–120 minutes.

[0071] Composite material preparation

[0072] The prepreg prepared above is cut and layered according to the designed layup direction and placed on the mold surface. After being vacuum-sealed, it is placed in an autoclave for curing. The curing process conditions are: autoclave pressure 0.4~0.7MPa, vacuum degree ≤-0.095MPa, curing temperature 120~190℃ (the specific temperature depends on different types of curing agents and accelerators), and holding time 30~120 minutes. After curing, it is naturally cooled to below 60℃, the pressure is released, and the mold is demolded to obtain T700 carbon fiber reinforced epoxy resin composite material.

[0073] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0074] Example 1

[0075] Adhesive formulation

[0076] 100g of main resin (bisphenol A type epoxy resin), 8g of toughening agent (cyano-containing polyethersulfone with formula I structure, number average molecular weight 35,000, Mw 50,000), 8g of carboxyl-terminated butadiene-acrylonitrile rubber (number average molecular weight Mn of 3550, acrylonitrile mass fraction of 18%), 2g of filler (silica), 5g of curing agent (dicyandiamide), and 1g of accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)).

[0077] Preparation method:

[0078] preparation of adhesive solution

[0079] First, the cyano-containing polyethersulfone toughening agent and carboxyl-terminated butadiene-acrylonitrile rubber are added to bisphenol A type epoxy at 120°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0080] Subsequently, the system temperature was lowered to 60°C, filler (silica) was added, and the mixture was stirred at a dispersion speed of 1000 RPM for 60 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0081] Next, add the curing agent (dicyandiamide) at 60°C and stir at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0082] Finally, the accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)) was added at 60°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0083] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0084] Prepreg preparation

[0085] First, the epoxy resin matrix is ​​formed into a film using a film-forming machine: the epoxy resin matrix is ​​transported to the coating head by a metering pump and uniformly coated onto the release paper at 70°C. The film thickness is controlled by a doctor blade or roller coating method. After cooling and shaping by a cooling roller, the film is wound up to obtain an epoxy resin film with uniform thickness.

[0086] Then, T700S carbon fiber is used as the reinforcing material. After unwinding through a yarn unwinding frame, the fiber is evenly spread. The above-mentioned adhesive film and fiber are then laminated in a laminating device: typically, a double-film method is used to hold the fiber, with one film on the top and bottom layers and a uniformly spread carbon fiber bundle in the middle. The laminate is heated and pressurized by a heating roller (100℃) to melt the adhesive film and fully impregnate the fiber. The laminated prepreg is cooled and shaped by a cooling roller and then wound by a release paper winding device to obtain a dry prepreg with uniform width and no defects.

[0087] Composite material preparation

[0088] The prepreg prepared above was cut and layered according to the designed layup direction and placed on the mold surface. After being sealed in a vacuum bag, it was placed in an autoclave for curing. The curing process conditions were: autoclave pressure 0.6 MPa, vacuum bag vacuum degree ≤ -0.095 MPa, curing temperature 150℃, and holding time for 30 minutes. After curing, it was allowed to cool naturally to below 60℃ before depressurization and demolding to obtain T700 carbon fiber reinforced epoxy resin composite material.

[0089] Example 2

[0090] Adhesive formulation

[0091] 100g of main resin (bisphenol A type epoxy resin), 8g of toughening agent (cyano-containing polyethersulfone of formula I, number average molecular weight 35,000, Mw 50,000), 8g of carboxyl-terminated butadiene-acrylonitrile rubber (number average molecular weight Mn of 3550, acrylonitrile mass fraction of 18%), 2g of filler (silica), 5g of curing agent (dicyandiamide), 1g of accelerator (2-methylimidazole), and 30g of solvent (N,N-dimethylformamide).

[0092] Preparation method:

[0093] preparation of adhesive solution

[0094] First, the cyano-containing polyethersulfone toughening agent and carboxyl-terminated butadiene-acrylonitrile rubber are added to a bisphenol A type epoxy and N,N-dimethylformamide solution at 50°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0095] Subsequently, at 50°C, filler (silica) was added and stirred at a dispersion speed of 1000 RPM for 60 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0096] Next, add the curing agent (dicyandiamide) at 50°C and stir at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0097] Finally, the accelerator (2-methylimidazole) was added at 50°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0098] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0099] Prepreg preparation

[0100] The epoxy resin matrix is ​​transferred to the adhesive bath of the prepreg production line, and the adhesive temperature is maintained at 50°C. T700S carbon fiber is used as the reinforcing material and is introduced into the adhesive bath via guide rollers to ensure uniform impregnation of the fibers with the adhesive. The impregnated fibers are then passed through extrusion rollers to control the resin content. Subsequently, the fibers are heated within a temperature range of 170°C to remove solvents from the adhesive and achieve pre-curing (B-stage curing). Finally, the fibers are cooled by cooling rollers, laminated with release paper, and wound by a winding device to obtain a prepreg with uniform width and no defects.

[0101] Composite material preparation

[0102] The prepreg prepared above was cut and layered according to the designed layup direction and placed on the mold surface. After being sealed in a vacuum bag, it was placed in an autoclave for curing. The curing conditions were: autoclave pressure 0.6 MPa, vacuum bag vacuum degree ≤ -0.095 MPa, curing temperature 170℃, and holding time for 60 minutes. After curing, it was allowed to cool naturally to below 60℃ before depressurization and demolding to obtain T700 carbon fiber reinforced epoxy resin composite material.

[0103] Example 3

[0104] Adhesive formulation

[0105] Main resins: 50g bisphenol F type epoxy resin, 50g phenolic epoxy resin, 10g toughening agent (cyano-containing polyethersulfone of formula I, number average molecular weight 23,000, weight average molecular weight 30,000), 6g carboxyl-terminated butadiene-acrylonitrile rubber (number average molecular weight Mn of 3,800, acrylonitrile mass fraction of 10%), 1g filler (alumina), 85g curing agent (methyltetrahydrophthalic anhydride), and 1g accelerator (benzyl dimethylamine).

[0106] Preparation method:

[0107] preparation of adhesive solution

[0108] First, the cyano-containing polyethersulfone toughening agent and carboxyl-terminated butadiene-acrylonitrile rubber are added to bisphenol F type epoxy and phenolic epoxy resin at 120°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0109] Subsequently, the system temperature was lowered to 70°C, filler (alumina) was added, and the mixture was stirred at a dispersion speed of 1000 RPM for 60 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0110] Next, the curing agent (methyltetrahydrophthalic anhydride) was added at a temperature of 50°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin were fully and evenly mixed.

[0111] Finally, the accelerator (benzyl dimethylamine) was added at 50°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0112] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0113] Prepreg preparation

[0114] First, the epoxy resin matrix is ​​formed into a film using a film-forming machine: the epoxy resin matrix is ​​transported to the coating head by a metering pump and uniformly coated onto the release paper at 100°C. The film thickness is controlled by a doctor blade or roller coating method. After cooling and shaping by a cooling roller, the film is wound up to obtain an epoxy resin film with uniform thickness.

[0115] Then, T700S carbon fiber is used as the reinforcing material. After unwinding through a yarn unwinding frame, the fiber is evenly spread. The above-mentioned adhesive film and fiber are then laminated in a laminating device: typically, a double-film method is used to hold the fiber, with one film on the top and bottom layers and a uniformly spread carbon fiber bundle in the middle. The laminate is heated and pressurized by a heating roller (130°C) to melt the adhesive film and fully impregnate the fiber. The laminated prepreg is cooled and shaped by a cooling roller and then wound by a release paper winding device to obtain a dry prepreg with uniform width and no defects.

[0116] Composite material preparation

[0117] The prepreg prepared above was cut and layered according to the designed layup direction and placed on the mold surface. After being sealed in a vacuum bag, it was placed in an autoclave for curing. The curing process conditions were: autoclave pressure 0.5 MPa, vacuum bag vacuum degree ≤ -0.095 MPa, curing temperature 120℃, and holding time 120 minutes. After curing, it was allowed to cool naturally to below 60℃ before depressurization and demolding to obtain T700 carbon fiber reinforced epoxy resin composite material.

[0118] Comparative Example 1

[0119] Adhesive formulation

[0120] 100g of main resin (bisphenol A type epoxy resin), 2g of filler (silica), 5g of curing agent (dicyandiamide), and 1g of accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)).

[0121] Preparation method:

[0122] preparation of adhesive solution

[0123] First, the filler (silica) is added to bisphenol A epoxy at 60°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure uniform dispersion of the filler.

[0124] Next, add the curing agent (dicyandiamide) at 60°C and stir at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0125] Finally, the accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)) was added at 60°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0126] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0127] Prepreg preparation

[0128] Same as Example 1.

[0129] Composite material preparation

[0130] Same as Example 1.

[0131] Comparative Example 2

[0132] Adhesive formulation

[0133] 100g of main resin (bisphenol A type epoxy resin), 8g of toughening agent (cyano-containing polyethersulfone of formula I, number average molecular weight 35,000, Mw 50,000), 2g of filler (silica), 5g of curing agent (dicyandiamide), and 1g of accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)).

[0134] Preparation method:

[0135] preparation of adhesive solution

[0136] First, the cyano-containing polyethersulfone toughening agent is added to the bisphenol A type epoxy at 120°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0137] Subsequently, the system temperature was lowered to 60°C, filler (silica) was added, and the mixture was stirred at a dispersion speed of 1000 RPM for 60 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0138] Next, add the curing agent (dicyandiamide) at 60°C and stir at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0139] Finally, the accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)) was added at 60°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0140] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0141] Prepreg preparation

[0142] Same as Example 1.

[0143] Composite material preparation

[0144] Same as Example 1.

[0145] Comparative Example 3

[0146] Adhesive formulation

[0147] 100g of main resin (bisphenol A type epoxy resin), 8g of carboxyl-terminated butadiene-acrylonitrile rubber (number average molecular weight Mn of 3550, acrylonitrile mass fraction of 18%), 2g of filler (silica), 5g of curing agent (dicyandiamide), and 1g of accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)).

[0148] Preparation method:

[0149] preparation of adhesive solution

[0150] First, the carboxyl-terminated butadiene-acrylonitrile rubber is added to bisphenol A type epoxy at 120°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0151] Subsequently, the system temperature was lowered to 60°C, filler (silica) was added, and the mixture was stirred at a dispersion speed of 1000 RPM for 60 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0152] Next, add the curing agent (dicyandiamide) at 60°C and stir at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0153] Finally, the accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)) was added at 60°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0154] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0155] The preparation of the prepreg is the same as in Example 1.

[0156] The preparation of the composite material was the same as in Example 1.

[0157] Comparative Example 4

[0158] Adhesive formulation

[0159] 100g of main resin (bisphenol A type epoxy resin), 8g of polyethersulfone (number average molecular weight 35,000, Mw 50,000), 8g of carboxyl-terminated butadiene-acrylonitrile rubber (number average molecular weight Mn of 3,550, acrylonitrile mass fraction of 18%), 2g of filler (silica), 5g of curing agent (dicyandiamide), and 1g of accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)).

[0160] Preparation method:

[0161] preparation of adhesive solution

[0162] First, polyethersulfone and carboxyl-terminated nitrile rubber are added to bisphenol A epoxy at 120°C and mixed in a stirred tank at a dispersion speed of 800 RPM for 60 minutes to ensure that the toughening agent is fully dissolved or uniformly dispersed.

[0163] Subsequently, the system temperature was lowered to 60°C, filler (silica) was added, and the mixture was stirred at a dispersion speed of 1000 RPM for 60 minutes to ensure that the filler was uniformly dispersed in the resin system.

[0164] Next, add the curing agent (dicyandiamide) at 60°C and stir at a dispersion speed of 1000 RPM for 20 minutes to ensure that the curing agent and resin are fully and evenly mixed.

[0165] Finally, the accelerator (N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea)) was added at 60°C and stirred at a dispersion speed of 1000 RPM for 20 minutes to ensure that the accelerator was uniformly dispersed in the system.

[0166] After the above mixing process is completed, the resulting mixture is subjected to vacuum degassing to remove air bubbles entrained in the system, resulting in a homogeneous, bubble-free epoxy resin matrix.

[0167] Prepreg preparation

[0168] Same as Example 1.

[0169] Composite material preparation

[0170] Same as Example 1.

[0171] Performance comparison: The test results of the examples and comparative examples are detailed in Table 1.

[0172] Table 1. Test results of the examples and comparative examples.

[0173]

Claims

1. An epoxy resin matrix, characterized in that, The epoxy resin matrix comprises, by weight, the following components: epoxy resin: 100 parts; cyano-containing polyethersulfone: 5-20 parts; carboxyl-terminated nitrile rubber: 5-20 parts.

2. The epoxy resin matrix according to claim 1, characterized in that, The cyano-containing polyether sulfone has a weight-average molecular weight of 10,000 to 60,000 and a number-average molecular weight of 5,000 to 55,000; preferably, the cyano-containing polyether sulfone content is 8 to 20 parts.

3. The epoxy resin matrix according to claim 1 or 2, characterized in that, The number average molecular weight of the terminal carboxyl-terminated nitrile rubber is 2500-5000, and the mass fraction of acrylonitrile is 5-30%.

4. The epoxy resin matrix according to claim 1 or 2, characterized in that, The structure of the cyano-containing polyethersulfone toughening agent is shown in Formula I: Formula I.

5. The epoxy resin matrix according to claim 1 or 2, characterized in that, The epoxy resin matrix further comprises, by weight: curing agent: 2-100 parts; accelerator: 0.5-3 parts; filler: 0-30 parts; solvent: 0-200 parts.

6. The epoxy resin matrix according to claim 1 or 2, characterized in that, The epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and glycidylamine type epoxy resin.

7. The epoxy resin matrix according to claim 5, characterized in that, The curing agent is selected from at least one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, dicyandiamide, 4,4'-diaminodiphenylmethane, and boron trifluoride monoethylamine.

8. The epoxy resin matrix according to claim 5, characterized in that, The accelerator is selected from at least one of 2-methylimidazole, 4-methylimidazole, benzyldimethylamine, N,N''-(methylenedi-4,1-phenylene)bis(N',N'-dimethylurea), and 2-ethyl-4-methylimidazole.

9. The epoxy resin matrix according to claim 5, characterized in that, The filler is selected from at least one of talc, titanium dioxide, silicon dioxide, aluminum hydroxide, and aluminum oxide.

10. The epoxy resin matrix according to claim 5, characterized in that, The solvent is selected from at least one of dimethylformamide, acetone, butanone, toluene, xylene, propylene glycol methyl ether, ethylene glycol methyl ether, and cyclohexanone.

11. The method for preparing the epoxy resin matrix according to any one of claims 1 to 10, characterized in that, Includes the following steps: A. A mixture containing cyano polyethersulfone and carboxyl-terminated butadiene-acrylonitrile rubber is mixed with epoxy resin and solvent at 40-150°C to obtain mixture A; B. Cool the mixture A to 40-70℃, add the filler, mix thoroughly to obtain mixture B; C. Add curing agent to mixture B at 40-70℃ and mix evenly to obtain mixture C; D. Under conditions of 40–70°C, an accelerator is added to mixture C, the mixture is mixed evenly, and the mixture is degassed under vacuum to obtain the epoxy resin matrix; The preferred steps for uniform mixing include stirring at 800–1500 RPM for 30–60 minutes; for uniform mixing in step B, it includes stirring at 800–1500 RPM for 20–120 minutes; and for uniform mixing in steps C and D, it includes stirring at 800–1500 RPM for 20–40 minutes.

12. A prepreg, characterized in that, It includes reinforcing fibers and an epoxy resin matrix as described in any one of claims 1 to 10, wherein the epoxy resin matrix is ​​impregnated on the reinforcing fibers.

13. The prepreg according to claim 12, characterized in that, The reinforcing fiber is carbon fiber, preferably T700 grade carbon fiber.

14. A fiber-reinforced composite material, characterized in that, The fiber-reinforced composite material is obtained by curing and molding the prepreg as described in claim 12 or 13.

15. The fiber-reinforced composite material according to claim 14, characterized in that, The fiber-reinforced composite material has a tensile strength of 0° above 2800 MPa, a glass transition temperature (Tg) maintained at 120–140°C, and an interlaminar shear strength above 88 MPa.

16. The fiber-reinforced composite material according to claim 14, characterized in that, The curing pressure for the curing process is 0.4–0.7 MPa, the vacuum degree is ≤-0.095 MPa, the curing temperature is 120–190°C, and the curing time is 30–120 minutes.

Images