Reformable epoxy resin based composites, preparation and reforming method

Abstract

The application provides a repeatable molding epoxy resin-based composite material, a preparation method and a repeatable molding method. The composite material is prepared from reinforced fibers, epoxy resin monomers, a chain extender, a tertiary amine catalyst and an acid anhydride curing agent. The chain extender is a small molecule amine compound, and the small molecule amine compound contains two active N-H bonds in the structural formula. The repeatable molding epoxy resin-based composite material can effectively control the viscosity of the resin glue liquid after the chain extender and the epoxy resin monomers are prepolymerized to prepare a prepreg and then a composite material. In addition, the repeatable molding epoxy resin composite material can be used as other composite structural parts after being hot-pressed and re-molded, realizing recycling of over-aged composite materials, significantly reducing energy consumption, and significantly improving the recycling efficiency of high-cost carbon fibers and other raw materials.

Description

Technical Field

[0001] This invention relates to the field of organic materials, and more particularly to reconfigurable epoxy resin-based composite materials, their preparation and reconfiguration methods. Background Technology

[0002] Currently, epoxy resin-based thermosetting composites dominate the automotive, aerospace, and sporting goods industries due to their excellent mechanical properties and weather resistance. However, after their service life, most of these components are disposed of through incineration or landfill, with only a small amount being crushed and used as filler. This not only results in significant energy waste but also leads to insufficient resource utilization. In recent years, with the development of self-healing resin systems based on dynamic chemical bonds such as ester exchange and imine exchange, solvent degradation-fiber recycling technology has become a research hotspot. However, this technology still faces a key bottleneck: while solvent treatment can effectively dissociate fibers from the resin matrix, it causes the fibers to lose their original orientation structure, forming a disordered entanglement state, which significantly degrades their mechanical properties, making it difficult to meet the reuse requirements of high-performance composite materials. This core issue severely restricts the secondary application value of recycled fibers in high-end fields.

[0003] Therefore, the remolding and recycling technology for epoxy resin-based thermosetting composite components not only enables efficient resource recycling but also significantly reduces energy consumption and carbon emissions in material production, possessing both outstanding economic value and environmental benefits. However, current self-healing systems based on anhydride-cured epoxy resins still face technical bottlenecks, making it difficult to meet the process requirements for prepreg preparation. This deficiency severely restricts the industrial application of this material in high-end recycling fields. Summary of the Invention

[0004] The main objective of this invention is to provide a reconfigurable epoxy resin-based composite material, its preparation, and a reconfigurable method, in order to solve the technical problem that self-healing systems based on anhydride-cured epoxy resins cannot meet the process requirements for prepreg preparation.

[0005] To achieve the above objectives, this application provides a reproducible epoxy resin-based composite material, which is prepared from reinforcing fibers, epoxy resin monomers, chain extenders, tertiary amine catalysts, and acid anhydride curing agents. The chain extender is a small molecule amine compound, and the structural formula of the small molecule amine compound includes two active NH bonds.

[0006] According to embodiments of this application, the reinforcing fiber includes at least one selected from carbon fiber, glass fiber, aramid fiber, and ultra-high molecular weight polyethylene fiber. The epoxy resin monomer includes a resin monomer containing a diepoxy group. The tertiary amine catalyst includes a small molecule amine compound containing a tertiary amine structure. The acid anhydride curing agent includes a small molecule curing agent containing organic acid anhydride groups.

[0007] This application also provides a method for preparing a repeatable epoxy resin-based composite material, comprising the following steps:

[0008] (1) Mix epoxy resin monomer with chain extender, heat for 5 min-5 h to prepolymerize, and fully react to obtain prepolymer.

[0009] (2) After the temperature of the prepolymer decreases, the prepolymer and the tertiary amine catalyst are mixed evenly and then the curing agent is added to obtain a mixed resin system.

[0010] (3) The mixed resin system obtained in step (2) is combined with reinforcing fibers to prepare a prepreg.

[0011] (4) The prepreg is laid into the mold and hot-pressed and cured in two stages to obtain a repeatable epoxy resin-based composite material. The first stage is cured at 60-140℃ for 1-4 hours, and the second stage is cured at 140-240℃ for 2-10 hours.

[0012] According to the embodiments of this application, at least one of the following conditions is met:

[0013] ①The molar ratio of the epoxy resin monomer to the chain extender is (5:1) to (100:1).

[0014] ②The molar ratio of the epoxy resin monomer to the tertiary amine catalyst is (5:1) to (50:1).

[0015] ③ The molar ratio of the epoxy resin monomer to the acid anhydride curing agent is (0.75:1) to (1.5:1).

[0016] According to embodiments of this application, the chain extender is a primary amine compound and / or a secondary amine compound.

[0017] The primary amine compounds include small organic amine compounds containing an active -NH2 group, including at least one of methylamine, ethylamine, propylamine, aniline, naphthylamine, and benzylamine.

[0018] The di-secondary amine compounds include small organic amine compounds containing two different active NH bonds, including at least one of N,N'-dimethylethylenediamine, N,N'-dimethylhexanediamine, N,N'-dimethyl-p-phenylenediamine, piperazine, and dimethylpiperazine.

[0019] According to embodiments of this application, the tertiary amine catalyst comprises at least one of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, triethylamine, dimethylaniline, and triethanolamine.

[0020] According to embodiments of this application, the anhydride curing agent includes at least one of methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, phthalic anhydride, pyromellitic dianhydride, hexahydrobenzoic dianhydride, maleic anhydride, glutaric anhydride, and nadic anhydride.

[0021] According to embodiments of this application, the epoxy resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenolic epoxy resin, and polyether epoxy resin.

[0022] This application also provides a method for repeatedly shaping reusable epoxy resin-based composite materials, comprising the following steps:

[0023] The above-mentioned re-molded epoxy resin-based composite material is placed on the target mold and kept at 200℃~220℃ for 30 minutes. The temperature is maintained and the re-molded epoxy resin-based composite material is pressurized and re-molded to obtain a secondary molded composite material plate.

[0024] According to the embodiments of this application, in the pressurization step, the pressurization pressure is 0.1~2MPa and the pressurization time is 0.5~4h.

[0025] The aforementioned reconfigurable epoxy resin-based composite material, after prepolymerization of the chain extender and epoxy resin monomer, can effectively control the viscosity of the resin solution to prepare prepreg, and then to prepare the composite material. Simultaneously, the chain extender, after prepolymerization with the epoxy resin, can also generate tertiary amines, which act as catalysts for transesterification reactions, thereby improving the efficiency of the transesterification reaction. Furthermore, the reconfigurable epoxy resin composite material, after hot pressing and reconfiguration, can be used for other composite material structural components, enabling the recycling of expired composite materials, significantly reducing energy consumption, and significantly improving the recycling efficiency of high-cost raw materials such as carbon fiber. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the viscosity-time relationship of a mixed resin system according to an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the viscosity-temperature relationship of a mixed resin system according to an embodiment of this application.

[0029] Figure 3These are physical images of a repeatable epoxy resin-based composite material plate and a secondary-shaped composite material plate according to an embodiment of this application.

[0030] Figure 4 These are physical images of a repeatable epoxy resin-based composite material plate and a secondary-shaped composite material plate according to an embodiment of this application.

[0031] Figure 5 This is a comparison diagram of the shear strength of a short beam from a re-molded epoxy resin-based composite material plate and a secondary-molded composite material plate according to an embodiment of this application.

[0032] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0035] The inventors conducted in-depth research on the self-healing system based on anhydride-cured epoxy resin. They discovered that although the material can achieve thermo-induced self-healing properties through transesterification after the addition of a catalyst, and possesses degradability in small-molecule hydroxyl solvents, its excessively low system viscosity and high surface tension lead to rapid shrinkage after coating, making it difficult to meet the process requirements for prepreg preparation. This defect severely restricts the industrial application of this material in the high-end recycling field.

[0036] Based on this, this application provides a reproducible epoxy resin-based composite material, which is prepared from reinforcing fibers, epoxy resin monomers, chain extenders, tertiary amine catalysts and acid anhydride curing agents. The chain extender is a small molecule amine compound, and the structural formula of the small molecule amine compound includes at least two NH bonds, which are located on the same N element or different N elements.

[0037] In this application, the small molecule amine compound is an amine compound with a molecular weight of less than 500. The structural formula of the small molecule amine compound includes at least two NH bonds. The purpose of the chain extender is to increase the chain length of the epoxy resin without increasing the crosslinking density, thereby improving toughness.

[0038] For example, if there are two NH bonds, and both NH bonds are located on the same N element, it is a monoprimary amine compound. If the two NH bonds are located on two separate N elements, it is a disecondary amine compound.

[0039] For example, the number of NH bonds is greater than two. All NH bonds must be located on at least two N elements. The groups corresponding to the aforementioned N elements are independently selected from primary amine groups and secondary amine groups, respectively.

[0040] In this application, the viscosity of the epoxy resin solution is adjusted by prepolymerizing a chain extender with epoxy resin monomers to suit the preparation of prepregs (such as the requirements for prepreg preparation using the film method), thereby preparing a composite material. The composite material is reproducibly shaped through the exchange reaction between free hydroxyl groups and ester bonds in the epoxy resin matrix, as shown in the following reaction structure.

[0041] .

[0042] The epoxy groups in the epoxy resin matrix undergo ring-opening to produce hydroxyl groups, which then form a cross-linked network after a curing and cross-linking reaction with the carboxyl groups in the curing agent. Most sites in this cross-linked network are ester bonds, which are reversible covalent bonds. Under certain conditions, hydroxyl and carboxyl groups can be regenerated. Based on this principle, repeated molding can be achieved through heating and pressurization.

[0043] The core of this invention lies in the fact that the chain extender, after prepolymerization with epoxy resin monomers, can effectively increase the viscosity of the resin solution, making it suitable for the preparation of prepregs using the film-forming method, and thus for the preparation of composite materials. Simultaneously, the chain extender, after prepolymerization with epoxy resin, can also generate tertiary amines, which act as catalysts for transesterification reactions, thereby improving the efficiency of the transesterification reaction. Furthermore, the reconfigurable epoxy resin composite material, after hot pressing and reconfiguration, can be used for other composite material structural components, achieving 100% recycling of expired composite materials.

[0044] The aforementioned reconfigurable epoxy resin-based composite material, after prepolymerization of the chain extender and epoxy resin monomer, can effectively control the viscosity of the resin solution to prepare prepreg, and then to prepare the composite material. Simultaneously, the chain extender, after prepolymerization with the epoxy resin, can also generate tertiary amines, which act as catalysts for transesterification reactions, thereby improving the efficiency of the transesterification reaction. Furthermore, the reconfigurable epoxy resin composite material, after hot pressing and reconfiguration, can be used for other composite material structural components, achieving 100% recycling of expired composite materials, significantly reducing energy consumption, and significantly improving the recycling efficiency of high-cost raw materials such as carbon fiber.

[0045] According to embodiments of this application, the reinforcing fiber includes at least one selected from carbon fiber, glass fiber, aramid fiber, and ultra-high molecular weight polyethylene fiber. The epoxy resin monomer includes a resin monomer containing a diepoxy group. The tertiary amine catalyst includes a small molecule amine compound containing a tertiary amine structure. The acid anhydride curing agent includes a small molecule curing agent containing organic acid anhydride groups.

[0046] This application also provides a method for preparing a repeatable epoxy resin-based composite material, comprising the following steps:

[0047] (1) Mix epoxy resin monomer with chain extender, heat for 5 min-5 h to prepolymerize, and fully react to obtain prepolymer.

[0048] In this step, a prepolymerization reaction occurs, adjusting the viscosity of the epoxy resin solution. A prepolymerization time ranging from 5 minutes to 8 hours allows for a more complete reaction between the chain extenders with varying reactivity and the epoxy resin, ensuring that the active NH bonds are essentially consumed, thus avoiding interference with the subsequent transesterification reaction.

[0049] (2) After the temperature of the prepolymer decreases, the prepolymer and the tertiary amine catalyst are mixed evenly and then the curing agent is added to obtain a mixed resin system.

[0050] In this step, if the temperature of the prepolymer is reduced to 50°C, the tertiary amine catalyst is added and mixed well, and then the curing agent is added.

[0051] (3) The mixed resin system obtained in step (2) is combined with reinforcing fibers to prepare a prepreg.

[0052] Alternatively, the mixed resin system can be degassed before preparing the prepreg. For example, the mixed resin system can be degassed in a vacuum oven.

[0053] There are two main methods for preparing prepregs: solution impregnation and film coating. In this step, the specific method for preparing the prepreg is not limited.

[0054] Solution impregnation involves impregnating fibers or fabrics with a resin solution, allowing the solvent in the resin to evaporate. During this process, the epoxy resin undergoes partial curing, changing its state from liquid to solid, thus forming a prepreg. This method requires minimal investment in production equipment.

[0055] The prepreg process involves first mixing resin with a curing agent to create a uniform and smooth film. Then, the prepreg film is sandwiched with fibers to form a core structure (typically a "sandwich" structure). Multiple sets of hot rollers are used to impregnate the fibers with resin, resulting in a prepreg. The advantages of this process include precise control of resin content, low volatile matter content, and no environmental pollution.

[0056] In the film-forming method, the preparation of the film typically involves: uniformly mixing a resin matrix and a curing agent, and then uniformly coating the mixture onto release paper using a coating device to produce a film of uniform thickness. During the preparation process, the film thickness can be precisely controlled by adjusting the spacing of the coating rollers and the running speed of the release paper.

[0057] (4) The prepreg is laid into the mold and hot-pressed and cured in two stages to obtain a repeatable epoxy resin-based composite material. The first stage is cured at 60-140℃ for 1-4 hours, and the second stage is cured at 140-240℃ for 2-10 hours.

[0058] In some embodiments, the prepreg is pre-cut into a certain shape (e.g., using a fabric cutter), and then manually laid into a mold. It is then placed in a vacuum bag and molded using methods such as autoclave molding, vacuum curing oven molding, or high-temperature compression molding.

[0059] In some embodiments, the molar ratio of the epoxy resin monomer to the chain extender is (5:1) to (100:1). In some specific embodiments, the molar ratio is (30:1) to (50:1), preferably (35:1) to (45:1), and more preferably (38:1) to (41:1).

[0060] In some embodiments, the molar ratio of the epoxy resin monomer to the tertiary amine catalyst is (5:1) to (50:1). In some specific embodiments, the molar ratio is (5:1) to (15:1), preferably (6:1) to (10:1), and more preferably (8:1) to (9:1).

[0061] In some embodiments, the molar ratio of the epoxy resin monomer to the anhydride curing agent is (0.75:1) to (1.5:1). In some specific embodiments, the molar ratio is (0.8:1) to (1.2:1), preferably (0.9:1) to (1.0:1).

[0062] According to embodiments of this application, the chain extender is a primary amine compound and / or a secondary amine compound.

[0063] The primary amine compounds include all small organic amine compounds containing an active -NH2 group, including but not limited to methylamine, ethylamine, propylamine, aniline, naphthylamine, benzylamine, etc. Benzylamine is preferred.

[0064] The diamine compound includes all small organic amine compounds containing two differently active NH bonds, including but not limited to N,N'-dimethylethylenediamine, N,N'-dimethylhexanediamine, N,N'-dimethyl-p-phenylenediamine, piperazine, dimethylpiperazine, etc. Preferably, it is 2,6-dimethylpiperazine.

[0065] In some embodiments, the tertiary amine catalyst comprises at least one selected from 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, triethylamine, dimethylaniline, and triethanolamine. Preferably, it is 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0066] In some embodiments, the anhydride curing agent includes at least one selected from methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, phthalic anhydride, pyromellitic dianhydride, hexahydrobenzoic dianhydride, maleic anhydride, glutaric anhydride, and nadic anhydride. Methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride are preferred.

[0067] In some embodiments, the epoxy resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenolic epoxy resin, and polyether epoxy resin.

[0068] This application also provides a method for repeatedly shaping reusable epoxy resin-based composite materials, comprising the following steps:

[0069] The above-mentioned re-molded epoxy resin-based composite material is placed on the target mold and kept at 200℃~220℃ for 30 minutes. The temperature is maintained and the re-molded epoxy resin-based composite material is pressurized and re-molded to obtain a secondary molded composite material plate.

[0070] It should be noted that the number of times the epoxy resin-based composite material can be repeatedly molded is greater than or equal to 2.

[0071] In some embodiments, during the pressurization step, the pressurization pressure is 0.1~2MPa and the pressurization duration is 0.5~4h.

[0072] The appropriate pressure and pressurization time should be selected based on the thickness of the re-molded epoxy resin matrix composite. For larger thicknesses, a relatively larger pressure and a longer pressurization time should be chosen. Conversely, for smaller thicknesses, a relatively smaller pressure and a shorter pressurization time should be chosen.

[0073] Example 1

[0074] The epoxy resin monomer was selected as bisphenol A epoxy resin (marked as E-51 in Example 1), the tertiary amine catalyst was selected as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (marked as TBD in Example 1), the chain extender was selected as 2,6-dimethylpiperazine (marked as 2,6-DMP in Example 1), and the acid anhydride curing agent was selected as methyltetrahydrophthalic anhydride (marked as MeTHPA in Example 1).

[0075] E-51 and 2,6-DMP were mixed evenly at a molar ratio of 40.77:1 and prepolymerized at 120℃ for 30 min. After the prepolymer cooled to 50℃, TBD powder was added to the prepolymer at a molar ratio of E-51 to TBD of 8.28:1 and mixed evenly. MeTHPA curing agent was added to the prepolymer at a molar ratio of E-51 to MeTHPA of 0.989:1 and stirred evenly to obtain a mixed resin system. After degassing the mixed system in a vacuum oven for 30 min, it was coated onto carbon fiber fabric at 42℃ using the film coating method to obtain a prepreg. The prepreg was cut using a prepreg cutting machine and then manually laid into a mold. It was cured in two stages at 0.6 MPa using a hot press. The first stage was cured at 120℃ for 2 h, and the second stage was cured at 180℃ for 4 h to obtain a highly repeatable epoxy resin-based composite material.

[0076] The viscosity-temperature and viscosity-time relationships of the mixed resin system were tested using a rotational rheometer. Viscosity is a material's ability to resist flow when subjected to shear force, and it varies with temperature. Viscosity-temperature testing assesses a material's flowability and processability by measuring the change in viscosity at different temperatures. For most fluids and viscous materials, viscosity decreases with increasing temperature. Viscosity-time testing assesses a material's flowability and processability by measuring the change in viscosity at a given temperature over different time periods. See also Figure 1 and Figure 2 The viscosity-temperature test was conducted at a temperature range of 30-120℃ with a heating rate of 2℃ / min. The viscosity-temperature curve showed that in this embodiment, the viscosity of the resin mixture decreased with increasing temperature before 87℃, then increased with increasing temperature after 87℃, and finally increased sharply after 110℃, eventually leading to initial curing. Since the processing temperature of the composite prepreg in this embodiment was 42℃, the viscosity-temperature test was conducted at 50℃ for 3 hours. The viscosity-temperature curve showed that the resin viscosity increased linearly with time at 50℃ within 3 hours. After 3 hours (10800s), the resin viscosity reached 184257.6 mPa·s and did not cure, indicating that the resin in this embodiment has excellent processing performance during the preparation of the prepreg.

[0077] The mechanical properties of the repeatable-shaped epoxy resin matrix composites were characterized by tensile testing. The tensile testing standard followed ASTM D3039. For unidirectional 0° testing, the sample size was 250 mm × 15 mm × 1 mm; for unidirectional 90° testing, the sample size was 175 mm × 25 mm × 2 mm. Five repeated tests were performed on the same set of samples. As shown in Table 1, the average tensile strength of the repeatable-shaped epoxy resin matrix composites at unidirectional 0° was 2.12 GPa, and the elastic modulus was 139.55 GPa.

[0078] Table 1 Results of single-piece tensile tests at 0°

[0079]

[0080] According to Table 2, the average tensile strength of the unidirectional 90° repeatable epoxy resin matrix composite material is 24.88 MPa, and the tensile modulus is 6.49 GPa.

[0081] Table 2 Results of 90° Tensile Single-Piece Tests

[0082]

[0083] The above demonstrates the excellent mechanical properties of the reproducible epoxy resin-based composite material prepared in the examples.

[0084] Example 2

[0085] The epoxy resin monomer was selected as bisphenol A type epoxy resin (marked as E-51 in Example 2), the catalyst was selected as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (marked as TBD in Example 2), the chain extender was selected as benzylamine (marked as BnAm in Example 2), and the curing agent was selected as methylhexahydrophthalic anhydride (marked as MHHPA in Example 2).

[0086] E-51 and BnAm were mixed evenly at a molar ratio of 38.25:1 and prepolymerized at 120℃ for 20 minutes. After the prepolymer cooled to 50℃, TBD powder was added to the prepolymer at a molar ratio of E-51 to TBD of 8.28:1 and mixed evenly. Curing agent MHHPA was added to the prepolymer at a molar ratio of E-51 to MHHPA of 1:1 and stirred evenly to obtain a mixed resin system. After degassing the mixed system in a vacuum oven for 30 minutes, it was coated onto carbon fiber fabric at 40℃ using the film coating method to obtain a prepreg. The prepreg was cut using a prepreg cutting machine and then manually laid into a mold. It was cured in two stages at 0.6 MPa using a hot press. The first stage was cured at 120℃ for 2 hours and the second stage was cured at 180℃ for 4 hours to obtain a highly repeatable epoxy resin-based composite material.

[0087] Example 3

[0088] The repeatable-formable epoxy resin-based composite material plate prepared in Example 1 was cut into strip-shaped specimens using a high-speed water jet cutting instrument. The repeatable-formability test of the composite material was conducted in a universal testing machine equipped with an environmental chamber. This experiment was a repeatable-formation test using a 120° bend angle die, and the bending rate and force were controlled during the experiment to avoid fiber breakage in the composite material.

[0089] The composite material plate was first held at 220 °C for 30 min, during which a reversible transesterification reaction occurred, releasing the carboxyl groups of MeTHPA and the hydroxyl groups of E-51. Then, the composite material plate was reshaped by three-point bending at rates of 0.2 / 0.5 / 1 mm / min until the pressure increased to 0.6 MPa. It was then held at 220 °C for 30 min to allow for a full transesterification reaction, resulting in the re-crosslinking of MeTHPA and E-51, yielding the desired product. Figure 3 The secondary-shaped composite material plate shown, wherein, Figure 3 (a) is a secondary-shaped composite material plate. Figure 3 (b) is a repeatable epoxy resin-based composite material board. Figure 5 The short beam shear strength of the re-formed epoxy resin-based composite material plate before and after different forming rates is shown. It can be found that the short beam shear strength of the epoxy resin-based composite material plate after re-forming at rates of 0.2 / 0.5 / 1 mm / min is better than that of the epoxy resin-based composite material plate before forming. Therefore, the re-formed epoxy resin-based composite material of the present invention has good re-formability.

[0090] To simplify the experiment and further verify the repeatable shaping properties of the composite material, a 0.5 mm thick rectangular composite unidirectional plate was heated to 200 °C on an arc-shaped mold and held under pressure at 0.1 MPa for 2 hours, finally obtaining the following... Figure 4 The composite material plate shown is a secondary-shaped material, wherein, Figure 4 (a) is a secondary-shaped composite material plate. Figure 4 (b) is a repeatable epoxy resin-based composite material board.

[0091] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A reworkable epoxy resin based composite material, characterized in that, The repeatable shaped epoxy resin-based composite material is prepared from reinforcing fibers, epoxy resin monomers, chain extenders, tertiary amine catalysts and anhydride curing agents, wherein the chain extender is a small molecule amine compound, and the small molecule amine compound contains two active N-H bonds in the structural formula; The chain extender is a mono-primary amine compound and / or a bis-secondary amine compound; The mono-primary amine compound includes at least one of an organic small molecule amine compound containing one active -NH2, including methylamine, ethylamine, propylamine, aniline, naphthylamine, benzylamine; The bis-secondary amine compound includes at least one of an organic small molecule amine compound containing two different active N-H bonds, including N,N'-dimethylethylenediamine, N,N'-dimethylhexanediamine, N,N'-dimethyl-p-phenylenediamine, piperazine, dimethylpiperazine; The tertiary amine catalyst includes at least one of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, triethylamine, dimethyl aniline, triethanolamine; The preparation method of the repeatable shaped epoxy resin-based composite material includes the following steps: (1) uniformly mix the epoxy resin monomers and the chain extender, heat and pre-polymerize for 5 min-5 h, and fully react to obtain a prepolymer; (2) after the temperature of the prepolymer is reduced, uniformly mix the prepolymer and the tertiary amine catalyst, and then add a curing agent to obtain a mixed resin system; (3) the mixed resin system obtained in step (2) is used together with reinforcing fibers to prepare a prepreg; (4) the prepreg is laid in a mold and is heat-pressed and cured in two stages to obtain the repeatable shaped epoxy resin-based composite material, wherein the first stage is curing at 60-140 DEG C for 1-4 h, and the second stage is curing at 140-240 DEG C for 2-10 h.

2. The reworkable epoxy-based composite material of claim 1, wherein At least one of the following conditions is met: ① The molar ratio of the epoxy resin monomers to the chain extender is (5:1)-(100:1); ② The molar ratio of the epoxy resin monomers to the tertiary amine catalyst is (5:1)-(50:1); ③ The molar ratio of the epoxy resin monomers to the anhydride curing agent is (0.75:1)-(1.5:1).

3. The reworkable epoxy-based composite material of claim 1, wherein The anhydride curing agent includes at least one of methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, phthalic anhydride, pyromellitic dianhydride, hexahydrophthalic dianhydride, maleic anhydride, glutaric anhydride, and nadic anhydride.

4. The reworkable epoxy-based composite material of claim 1, wherein, The epoxy resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenolic epoxy resin, and polyether epoxy resin.

5. The reworkable epoxy-based composite material of claim 1, wherein The reinforcing fibers include at least one of carbon fibers, glass fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers; the epoxy resin monomers include resin monomers containing double epoxy groups; the tertiary amine catalyst includes small molecule amine compounds containing tertiary amine structures; and the anhydride curing agent includes small molecule curing agents containing organic anhydride groups.

6. A method of re-shaping a re-shapable epoxy resin based composite material, characterized in that, The method includes the following steps: The repeatable shaped epoxy resin based composite material in any one of claims 1-5 is placed on a target mold, after being kept at 200-220 DEG C for 30 min, the temperature is maintained to pressurize and reshape the repeatable shaped epoxy resin based composite material, to obtain a second shaped composite material plate.

7. The method of claim 6, wherein the method of re-shaping a re-shapeable epoxy-based composite material is characterized by, In the step of pressurizing, the pressure is 0.1-2 MPa, and the pressurizing time is 0.5-4 h.

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