Method for rapidly curing epoxy resin

Abstract

The invention relates to the field of resin-based carbon nanotube reinforced composite materials, in particular to a method for rapidly curing epoxy resin. Mixing epoxy resin, a curing agent and the solvent solution containing the carbon nanotubes, and curing to obtain a cured epoxy resin; the carbon nanotubes are dispersed into a resin matrix or a curing agent in a step-by-step graded dispersion manner, and finally, dispersion bodies which are randomly and uniformly distributed are formed in a resin system, so that a stable dispersion system is formed. The tensile strength, the bending strength, the interface shear strength and other mechanical properties of the resin and the fiber reinforced composite material thereof are effectively improved, meanwhile, the temperature resistance of the resin material can be improved, and through further research and development, the material is expected to be popularized and applied in the fields of aerospace, electronics and electric appliances and other fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of resin-based carbon nanotube reinforced composite materials, in particular to a method for rapid curing of epoxy resin. BACKGROUND

[0002] Epoxy resin has excellent mechanical properties, such as high elastic modulus and breaking strength, low creep and less environmental degradation, and is widely used as an adhesive, a coating, a structural material and a composite matrix, especially in the aerospace and electronics industries. However, epoxy resin itself is brittle, which makes it prone to micro-cracks in use, limiting its further application. In recent years, there have been extensive studies on toughening epoxy resin and various methods for toughening epoxy resin have emerged, such as thermoplastic resin toughening, inorganic nanoparticle toughening, interpenetrating polymer network toughening and flexible segment curing agent toughening. Due to the small size effect and surface effect of nanoparticles, physical and chemical interactions occur between the nanoparticles and the polymer segments after the addition of the nanoparticles, and the two are mixed at the molecular level, and the comprehensive performance of the system is improved. Carbon nanotubes are excellent nanoparticles for toughening epoxy resin due to their excellent mechanical properties.

[0003] For epoxy resin, curing agent is an essential and important component. It usually needs to be crosslinked with a curing agent to form a three-dimensional network structure of macromolecules before use, and the structure and quality of the curing agent directly affect the application effect of the epoxy resin. Traditional resins and systems usually have slow curing speed, resulting in low production efficiency, which greatly limits the mass production and application. Rapid curing is usually carried out at high temperature to improve the production and processing rate, but the high curing temperature leads to the re-aggregation of carbon nanotubes during the resin curing process, which reduces the comprehensive performance of the resin and limits the application of carbon nanotubes in the rapid curing resin system. SUMMARY

[0004] The present application provides a method for rapid curing of epoxy resin, which overcomes the aggregation of carbon nanotubes during the resin curing process, improves the comprehensive performance of the cured resin, and improves the production efficiency of the resin system in industrial applications.

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method for rapid curing of resin which is easy to prepare, widely applicable and simple to operate.

[0006] A method for rapid curing of epoxy resin, comprising epoxy resin, imidazole and primary amine curing agent and carbon nanotubes, the carbon nanotubes are randomly and uniformly distributed in the resin system, and the resin system can be cured within 40 minutes.

[0007] According to one aspect of the present application, a method for rapid curing of epoxy resin is provided, comprising the following steps:

[0008] mixing the epoxy resin, the curing agent, and the solvent solution containing carbon nanotubes, and curing to obtain an epoxy resin cured product;

[0009] The curing agent is selected from at least one of an imidazole curing agent and a primary amine curing agent.

[0010] The imidazole curing agent is selected from at least one of 2-ethyl-4-methylimidazole (2E4MI), 1-benzyl-2-methylimidazole (1B2MZ), and N-(3-aminopropyl)-imidazole (API).

[0011] The primary amine curing agent is selected from at least one of ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA).

[0012] The ratio of the imidazole curing agent to the primary amine curing agent in the curing agent is 4:1 to 1:1.

[0013] The compounding can further exert the synergistic effect of the curing agent, achieving rapid curing while ensuring the performance of the cured product. If necessary, an appropriate amount of an accelerator can be added to further improve the curing speed.

[0014] The mass ratio of the epoxy resin, the curing agent, and the carbon nanotubes in the solvent solution containing carbon nanotubes is 100:4 to 10:0.05 to 0.1.

[0015] The epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin.

[0016] The diameter of the carbon nanotubes is 10 to 20 nm.

[0017] The length of the carbon nanotubes is 5 to 20 μm.

[0018] The solvent is selected from at least one of benzyl alcohol and propylene glycol monomethyl ether.

[0019] In the solvent solution containing carbon nanotubes, the concentration of the carbon nanotubes is 0.5 to 2 wt%.

[0020] The curing temperature is 70 to 130°C.

[0021] The curing time is 20 to 40 min.

[0022] The curing includes multi-stage curing at different temperatures, and the curing schedule can be determined according to the DSC test results.

[0023] Optionally, the method further comprises the following steps:

[0024] dispersing the solvent solution containing carbon nanotubes in the epoxy resin, adding a curing agent, curing to obtain an epoxy resin cured product;

[0025] The dispersion is stepwise dispersion.

[0026] The stepwise dispersion comprises manual grinding-mechanical stirring-homogeneous dispersion-ultrasonic treatment.

[0027] The content of the carbon nanotubes is determined according to the requirement of improving the performance of the resin system, the carbon nanotubes are dispersed into the resin in a stepwise manner, the dispersion speed is faster and the dispersion effect is more stable, and the specific operation method is as follows: the dispersion of the carbon nanotubes in the resin is promoted by using the method of manual grinding-mechanical stirring (stirring at 300 rpm for 20 min)-homogeneous dispersion (homogeneous treatment at 11000 rpm for 20 min)-ultrasonic treatment (ultrasonic treatment at 200 W for 30 min), if the viscosity of the resin is too high, the resin can be heated appropriately to reduce the viscosity so as to improve the dispersion effect, and the temperature of the resin should be controlled below 60℃ during the dispersion process to prevent the carbon nanotubes from re-agglomerating due to the too high temperature of the resin.

[0028] When the epoxy resin comprises a plurality of different epoxy resins, the solvent solution containing carbon nanotubes is first dispersed in the epoxy resin with lower viscosity, and then the remaining epoxy resins are added, if the viscosity of the plurality of different epoxy resins is high, the solvent solution containing carbon nanotubes is first dispersed in the curing agent, and then mixed with the epoxy resin.

[0029] Defoaming is performed before curing. Different defoaming methods can be selected according to different application scenarios, such as adding a defoaming agent, vacuum defoaming, and standing defoaming, if there is no defoaming requirement, the curing and molding can be directly performed.

[0030] The advantages of the present application are:

[0031] The epoxy resin, the curing agent, and the solvent solution containing carbon nanotubes are mixed, and then cured to obtain an epoxy resin cured product; the carbon nanotubes are dispersed into the resin matrix or the curing agent in a stepwise manner, and finally form a random and uniform dispersion in the resin system, forming a stable dispersion system, this method not only improves the curing rate of the resin system, but also effectively improves the mechanical properties such as tensile strength, bending strength, and interfacial shear strength of the resin itself and the fiber reinforced composite material, and can improve the temperature resistance of the resin material, and through further research and development, it is expected to be popularized and applied in the fields of aerospace, electronics, and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A flow chart for preparing the carbon nanotube reinforced epoxy resin system. DETAILED DESCRIPTION

[0033] The application will be described in detail below with reference to examples, but the application is not limited to these examples.

[0034] Example 1

[0035] This example takes the modification of TDE-85 / E51 compound resin with carbon nanotube dispersion liquid as an example, and 2-ethyl-4-methylimidazole (2E4MI) is used for curing.

[0036] (1) Determination of epoxy resin curing agent: select appropriate epoxy resin according to product performance requirements and processing methods, and this example selects TDE-85 and E51 resin and compounding according to the ratio of 7:3.

[0037] (2) Selection of curing agent: limited by the curing time requirement, 2-ethyl-4-methylimidazole (2E4MI) is selected as the curing agent.

[0038] (3) Modification of resin system with carbon nanotubes:

[0039] This place adopts the method of multi-stage dispersion, the specific method is as follows:

[0040] a) According to the modification requirements, take an appropriate amount of carbon nanotube dispersion liquid, transfer the carbon nanotube dispersion liquid and 70 parts of TDE-85 resin to the grinding mortar for grinding treatment, use the shear force generated during grinding to preliminarily mix the carbon nanotube dispersion liquid with the TDE-85 resin, the grinding time can be reasonably adjusted according to the content of the carbon nanotube dispersion liquid and the weight of the resin, generally in 15-40 minutes.

[0041] b) Mechanical stirring (stirring at 300 rpm for 20 minutes) is performed on the above mixture to promote further dispersion of the carbon nanotubes. The stirred mixture has no non-uniform state visible to the naked eye. If the resin viscosity is too large, it can be appropriately heated to promote the dispersion of the carbon nanotubes.

[0042] c) Homogenize the dispersion liquid obtained in b) at a speed of 11000 rpm for 20 minutes to eliminate the uneven dispersion in step b).

[0043] d) Ultrasonic treatment is performed on the dispersion liquid described in c) at a power of 300W for 40 minutes to form a monodisperse solution of carbon nanotubes in TDE-85 resin.

[0044] e) Add 30 parts of E51 resin and 4 parts of 2-ethyl-4-methylimidazole (2E4MI) curing agent to the dispersed solution, and further mechanically stir to form the final mixture.

[0045] (4) Transfer the resin to a vacuum drying oven to remove the bubbles formed during mechanical stirring.

[0046] (5) After vacuum defoaming, the resin is cured, and the curing system is 90°C for 20 minutes and 120°C for 10 minutes to obtain the final resin casting cured product.

[0047] The tensile strength of the carbon nanotube modified epoxy resin casting prepared in the present embodiment is increased by 8.8% compared with that before modification, and the dispersibility of the carbon nanotubes in the resin after mechanical stirring and ultrasonic dispersion is good. The tensile strength of the blank sample and the resin casting modified by the carbon nanotubes is shown in Table 1.

[0048] Table 1 Comparison of tensile strength of TDE-85 / E51-imidazole resin casting before and after modification

[0049]

[0050] Example 2

[0051] In the present embodiment, carbon nanotube dispersion liquid is used to modify and reinforce TDE-85 / E51 compounded resin, 2-ethyl-4-methylimidazole (2E4MI) is used for curing, and T700 carbon fiber is used as reinforcing body to prepare carbon fiber reinforced resin matrix composite material.

[0052] (1) Determination of epoxy resin curing agent: select appropriate epoxy resin according to product performance requirements and processing methods, TDE-85 and E51 resin are selected in the present embodiment and compounded according to the ratio of 7:3.

[0053] (2) Selection of curing agent: limited by the curing time requirement, 2-ethyl-4-methylimidazole (2E4MI) is selected as the curing agent.

[0054] (3) Modification of resin system by carbon nanotubes:

[0055] Here, a multi-stage dispersion method is used, and the specific method is as follows:

[0056] a) According to the modification requirements, an appropriate amount of carbon nanotube dispersion liquid is weighed, and the carbon nanotube dispersion liquid and 70 parts of TDE-85 resin are transferred to a grinding mortar for grinding treatment. The shear force generated during grinding is used to preliminarily mix the carbon nanotube dispersion liquid and the TDE-85 resin. The grinding time can be reasonably adjusted according to the content of the carbon nanotube dispersion liquid and the weight of the resin, and generally it is appropriate to be 15-40 minutes.

[0057] b) The mixture is subjected to mechanical stirring (stirring at a speed of 300 rpm for 20 minutes) to promote further dispersion of the carbon nanotubes. The stirred mixture has no non-uniform state visible to the naked eye. If the resin viscosity is too large, it can be appropriately heated to promote the dispersion of the carbon nanotubes.

[0058] c) homogenize the dispersion obtained in b) at 11000 rpm for 20 minutes to eliminate the non-uniform dispersion in step b).

[0059] d) ultrasonic treatment of the dispersion in c) at 300 W for 40 minutes to form a monodisperse solution of carbon nanotubes in TDE-85 resin.

[0060] e) adding 30 parts of E51 resin and 4 parts of 2-ethyl-4-methylimidazole (2E4MI) curing agent to the dispersed solution and further mechanically stirring to form a final mixture.

[0061] (4) transferring the resin to a vacuum drying oven to remove the air bubbles formed during the mechanical stirring process.

[0062] (5) applying a certain amount of resin between the layers of T700 carbon fiber unidirectional woven cloth to prepare a carbon fiber reinforced resin matrix composite laminate by a wet molding process, the curing process being 90°C for 20 minutes and 120°C for 10 minutes, and cutting the sample according to GB / T 2567-2008 and testing the bending performance.

[0063] The test results of the composite material prepared in this embodiment are shown in Table 2, and the bending strength of the composite material after adding carbon nanotubes is increased by 10.69% compared with before modification.

[0064] Table 2 Comparison of bending strength of TDE-85 / E51-Imidazole carbon fiber composite materials before and after modification

[0065]

[0066]

[0067] Example 3

[0068] In this embodiment, carbon nanotube dispersion is used to modify the E51 resin, and modified dicyandiamide is used as a curing agent.

[0069] (1) Determination of epoxy resin curing agent: select the appropriate epoxy resin according to the product performance requirements and processing methods, and E51 resin is selected in this embodiment.

[0070] (2) Selection of curing agent: limited by the curing time requirement, modified dicyandiamide is selected as the curing agent.

[0071] (3) modification of the resin system by carbon nanotubes:

[0072] Here, a multi-stage dispersion method is used, and the specific method is as follows:

[0073] a) according to the modified requirements, the appropriate amount of carbon nanotube dispersion liquid is weighed, the appropriate amount of carbon nanotube dispersion liquid and 100 parts of E51 resin are transferred to a grinding bowl for grinding treatment, and the shear force generated during grinding is used to preliminarily mix the carbon nanotube dispersion liquid with the E51 resin. The grinding time can be reasonably adjusted according to the content of the carbon nanotube dispersion liquid and the weight of the resin, and generally it is appropriate to be 15-40 minutes.

[0074] b) The mixture is subjected to mechanical stirring (stirring treatment at a speed of 300 rpm for 20 minutes) to promote further dispersion of the carbon nanotubes, and the stirred mixture has no non-uniform state visible to the naked eye.

[0075] c) The dispersion liquid obtained in b) is subjected to homogenization treatment at a speed of 11000 rpm for 20 minutes to further eliminate the uneven dispersion in the step b).

[0076] d) The dispersion liquid in c) is subjected to ultrasonic treatment at a power of 300 W for 40 minutes to form a monodisperse solution of carbon nanotubes in E51 resin.

[0077] e) 20 parts of modified dicyandiamide curing agent are added to the dispersed solution, and further mechanical stirring is performed to form a final mixture.

[0078] (4) The resin is transferred to a vacuum drying oven for vacuum treatment to remove the bubbles formed during mechanical stirring.

[0079] (5) The resin obtained in step (4) is cured, and the curing system is 100°C for 20 minutes, 140°C for 20 minutes, and then the mechanical properties are tested.

[0080] The mechanical property test results of the embodiment are shown in Table 3. Compared with the unmodified epoxy resin cast body, the tensile strength of the cast body after adding carbon nanotubes is increased by 23.69%.

[0081] Table 3 Comparison of tensile strength of E51-modified dicyandiamide resin cast body before and after modification

[0082]

[0083] The steps and advantages of the present application are set forth and shown in the summary of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the knowledge described in the above examples and the specification illustrates the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for rapid curing of epoxy resin, characterized in that, comprising the steps of: mixing an epoxy resin, a curing agent, and a solvent solution containing carbon nanotubes, and curing to obtain an epoxy resin cured product; the curing agent is selected from at least one of imidazole curing agent and primary amine curing agent; the imidazole curing agent is selected from at least one of 2-ethyl-4-methylimidazole (2E4MI), 1-benzyl-2-methylimidazole (1B2MZ), and N-(3-aminopropyl)-imidazole (API); the primary amine curing agent is selected from at least one of ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA). 2.The method for rapid curing of epoxy resin according to claim 1, characterized in that, the ratio of imidazole curing agent to primary amine curing agent in the curing agent is 4:1 to 1:1; the mass ratio of the epoxy resin, the curing agent, and the carbon nanotubes in the solvent solution containing carbon nanotubes is 100:4 to 10:0.05 to 0.

1. 3.The method for rapid curing of epoxy resin according to claim 1, characterized in that, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin. 4.The method for rapid curing of epoxy resin according to claim 1, characterized in that, the diameter of the carbon nanotubes is 10 to 20 nm; the length of the carbon nanotubes is 5 to 20 μm. 5.The method for rapid curing of epoxy resin according to claim 1, characterized in that, the solvent is selected from at least one of benzyl alcohol and propylene glycol monomethyl ether. 6.The method for rapid curing of epoxy resin according to claim 1, characterized in that, the concentration of the carbon nanotubes in the solvent solution containing carbon nanotubes is 0.5 to 2 wt%. 7.The method for rapid curing of epoxy resin according to claim 1, characterized in that, the curing temperature is 70 to 130 ℃; the curing time is 20 to 40 min; the curing comprises multi-stage curing at different temperatures. 8.The method for rapid curing of epoxy resin according to claim 1, characterized in that, comprising the steps of: dispersing the solvent solution containing carbon nanotubes in the epoxy resin, adding the curing agent, and curing to obtain an epoxy resin cured product; the dispersing is stepwise dispersing; the stepwise dispersing comprises hand grinding-mechanical stirring-homogeneous dispersing-ultrasonic treatment. 9.The method for rapid curing of epoxy resin according to claim 8, characterized in that, when multiple different epoxy resins are included in the epoxy resin, the solvent solution containing carbon nanotubes is first dispersed in the epoxy resin with lower viscosity, and then the remaining epoxy resins are added; if the viscosities of the multiple different epoxy resins are all high, the solvent solution containing carbon nanotubes is first dispersed in the curing agent, and then mixed with the epoxy resin. 10.The method for rapid curing of epoxy resin according to claim 1, characterized in that, defoaming is performed before the curing.

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