Novel epoxy resin as well as preparation method and application thereof

Abstract

The invention discloses novel epoxy resin, a preparation method thereof and application of the novel epoxy resin in preparation of a composite material. The epoxy resin is prepared from dihydrazide, vanillin, an epoxy monomer and an accelerant through a one-pot method. The acylhydrazone bond in the system endows the material with excellent dynamic properties, so that the material can be reprocessed and recycled under specific conditions. Meanwhile, the prepared epoxy resin (AZH-EP) has excellent thermal stability and mechanical properties. The composite material (AZH-EP / CF) prepared by combining the composite material with carbon fibers not only has excellent mechanical properties, but also can be degraded, recycled and repaired, so that the service life of the material is effectively prolonged, and the recycling rate of the material is effectively increased. In the invention, the preparation of the material does not need the participation of a solvent, and is green, environment-friendly and sustainable. Meanwhile, the material is prepared by a one-pot method, so that the energy consumption is low and the operation is simple. The epoxy composite material has important significance in promoting the practical application of the epoxy composite material in the fields of automobile lightweight, wind driven generator blades, aerospace and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resin materials, and relates to a novel epoxy resin and a preparation method and application thereof, and in particular to a preparation method of a high-performance, degradable, recyclable and self-repairable epoxy resin and a composite material thereof. Background Art

[0002] Epoxy resin is widely used in many fields such as wind turbine blades, electronic equipment, aerospace, floor paint, etc. due to its excellent chemical stability, good mechanical properties, high heat resistance and water resistance, and easy processing and adjustment performance. However, at present, most synthetic polymers are mainly focused on the realization of high performance and durability at the beginning of design, ignoring the consideration of repair, degradation and recycling, which makes it difficult to recycle such materials. This problem is increasingly prominent in practical applications. CN112608452 A synthesizes a modified polyamine curing agent with a borate bridging group, and uses the introduction of amine curing agents and accelerators to construct borate crosslinking points containing N→B coordination bonds to prepare an epoxy resin based on borate metathesis reaction, and prepares a high-performance, recyclable and easy-to-repair epoxy resin. However, there is the participation of solvents in its synthesis, and at the same time, the thermal properties of the prepared material are general, and the Tg can only reach 120°C at most. CN116333265 A synthesizes a curing agent containing a Schiff base structure using aromatic oxalaldehyde and p-aminophenol as raw materials, and the curing agent reacts with DGEBA to prepare an epoxy resin / glass fiber wind turbine blade composite material, but a large amount of solvent is required in the preparation process. This method also requires the use of a large amount of solvent in the preparation process, which is not conducive to environmental protection and will increase production costs.

[0003] Among various polymer composites, carbon fiber reinforced polymer composites (CFRCs) play a vital role in automotive lightweighting, wind turbine blades and aerospace applications. Epoxy resin-based CFRCs have excellent durability, high tensile strength and high Young's modulus. However, due to the permanent 3D cross-linking of thermosetting binders, CFRCs are difficult to depolymerize and recycle. This not only causes serious environmental pollution problems, but also results in a huge waste of thermosetting resins and expensive carbon fibers. In order to meet the growing demand for a sustainable polymer economy, new recyclable polymers must be developed to achieve the recycling of carbon fibers and thermosetting resins to maximize their value.

[0004] Based on this, a method for preparing an epoxy resin and its composite material that is environmentally friendly, high-performance, biodegradable, recyclable and self-repairable is urgently needed in the art. Summary of the invention

[0005] In view of the above deficiencies, the present invention proposes a preparation method of a high-performance, degradable, recyclable and self-healing epoxy resin and its composite material, which is prepared by a one-pot method using dihydrazide, vanillin, epoxy monomer and accelerator. The acylhydrazone bonds in the system endow the material with excellent dynamics, enabling the material to be reprocessed and recycled under specific conditions. At the same time, the prepared epoxy resin has excellent thermal stability and mechanical properties. The composite material (AZH-EP / CF) prepared by combining it with carbon fiber not only has excellent mechanical properties, but also can be degraded, recycled and repaired, effectively improving the service life and recycling rate of the material. In the present invention, the preparation of the material does not require the participation of solvents, which is green, environmentally friendly and sustainable. At the same time, the one-pot method for preparing this material has low energy consumption and simple operation. The present invention is achieved by the following technical means:

[0006] The present invention first discloses a preparation method of a novel epoxy resin, comprising the following steps:

[0007] React isophthalyl dimethoxyacetyl hydrazide with aldehyde at 70 °C for 2 h, then raise the temperature to 90 - 120 °C, add bisphenol A epoxy resin monomer and mix evenly to obtain a first mixture;

[0008] Add an accelerator to the first mixture and mix evenly to obtain a second mixture;

[0009] Place the second mixture in a mold, evacuate at 90 - 120 °C for 5 min, and cure by stepwise temperature rise to obtain a novel epoxy resin, named AZH-EP.

[0010] Further, the isophthalyl dimethoxyacetyl hydrazide, aldehyde, and bisphenol A epoxy resin are added in a molar ratio of 1:1:(1.5 - 2.5).

[0011] Further, the aldehyde is selected from one or more of: vanillin, m-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, o-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-3-ethoxybenzaldehyde.

[0012] Further, the bisphenol A epoxy resin monomer is selected from one or more of: bisphenol A diglycidyl ether BGEBA, epoxy E51, epoxy E44, epoxy E35, epoxy E20, NPES-601, NPES-901, NPES-902, NPES-903.

[0013] Further, the accelerator is selected from one or more of: 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-ethylimidazole; the mass of the accelerator is 0.5% - 2% of the total mass of the first mixture.

[0014] Furthermore, the stepwise temperature rise curing includes: curing at 90 - 120°C for 1 - 2 h; then raising the temperature to 160°C and curing for 1 - 2 h.

[0015] The present invention also discloses a novel epoxy resin (AZH-EP) prepared by any of the above preparation methods.

[0016] The present invention also discloses an application of the above novel epoxy resin in the preparation of a composite material (AZH-EP / CF), wherein:

[0017] The epoxy composite material (AZH-EP / CF) is prepared by the following method:

[0018] Fix the carbon fiber on a Teflon mold, and place the mold horizontally in an oven at 90°C - 120°C for standby;

[0019] According to the ratio of the above novel epoxy resin preparation, react isophthalyl dihydrazide and aldehyde at 70°C for 2 h, raise the temperature to 90°C - 120°C, add bisphenol A epoxy resin monomer and mix evenly to obtain a first mixture; add a promoter to the first mixture and mix evenly to obtain a second mixture; pour it into the Teflon mold, evacuate for 5 min at 90°C - 120°C, and hot press at 1 MPa for 1 - 2 h to obtain a prepreg. Before use, all samples are stored in a desiccator. The epoxy composite material (AZH-EP / CF) is obtained by hot pressing a certain number of layers of CFRP prepreg at 90 - 120°C and 1 MPa for 1 - 2 h, and then thermally curing at 160°C in an oven for 1 - 2 h according to actual needs.

[0020] Furthermore, the composite method includes: hand lay-up molding, spray molding, resin infusion, compression molding, vacuum infusion molding, pultrusion molding, prepreg method, vacuum autoclave method.

[0021] Furthermore, the carbon fiber is selected from one or more of: T300 carbon fiber, T400 carbon fiber, T700 carbon fiber, T800 carbon fiber, T1000 carbon fiber, M35 carbon fiber, M40 carbon fiber, M46 carbon fiber, M50 carbon fiber, M55 carbon fiber, M60 carbon fiber.

[0022] The present invention also discloses an epoxy composite material (AZH-EP / CF) prepared according to the above application.

[0023] The present invention also discloses an application of the epoxy composite material (AZH-EP / CF) prepared according to the above in the preparation of lightweight automobiles, wind turbines, and the aerospace field.

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention generates hydrazone dynamic covalent bonds in the resin curing crosslinking network to obtain an epoxy resin with high performance, degradability, recyclability, and self-healing properties, and uses it to prepare epoxy composites. The present invention uses a one-pot method to prepare epoxy resin, which has universality, high generality, mild reaction conditions, simple preparation process, and does not require other catalysts during recycling or repair. Based on the dynamic reversibility of the hydrazone bond, the resin can achieve good recycling and repair performance under certain heating conditions. In addition, compared with polymers crosslinked by other dynamic bond systems, the epoxy resin prepared in the present invention has excellent mechanical properties and thermal stability. At the same time, when it is prepared into an epoxy composite material, the obtained material can achieve double recycling of the resin and carbon fiber, enabling the epoxy composite material to have certain self-healing properties. At the same time, short-term degradation is realized, which is of great significance for promoting the practical application of such epoxy composite materials in the fields of automotive lightweight, wind turbine blades, and aerospace. Description of the Drawings

[0026] Figure 1 Tensile property test results of the epoxy resins prepared in Examples 1-3;

[0027] Figure 2 Dynamic thermomechanical property test results of the epoxy resins prepared in Examples 1-3;

[0028] Figure 3 Interlaminar shear strength test results of the epoxy resin carbon fiber composite material in Application Example 1. Detailed Description of the Invention

[0029] Example 1

[0030] A preparation method of a novel epoxy resin (AZH-EP), comprising:

[0031] The epoxy resin prepared in this experiment adopts a stepwise curing method. React isophthalic dimethoxyacethydrazide (1 mmol) and vanillin (1 mmol) at 70 °C for 2 h, then raise the temperature to 90 °C, add bisphenol A epoxy resin monomer (2.5 mmol) and mix evenly to obtain a first mixture; add accelerator 2-ethyl-4-methylimidazole (1% of the mass of the first mixture) to the first mixture and mix evenly to obtain a second mixture; then place it in a mold, evacuate at 120 °C for 5 min, cure at 120 °C for 2 h, and then raise the temperature to 160 °C and cure for 1 h to obtain a high-performance, degradable, recyclable, and self-healing epoxy resin (AZH-EP).

[0032] Example 2

[0033] A preparation method of a novel epoxy resin (AZH-EP), comprising:

[0034] The epoxy resin prepared in this experiment adopts a stepwise curing method. React isophthalic dimethoxyacetyl hydrazide (1 mmol) and vanillin (1 mmol) at 70 °C for 2 h, then raise the temperature to 90 °C, add bisphenol A epoxy resin monomer (2 mmol) and mix evenly to obtain the first mixture; add accelerator - 2 - ethyl - 4 - methylimidazole (1% of the mass of the first mixture) to the first mixture and mix evenly to obtain the second mixture; then place it in a mold, evacuate at 120 °C for 5 min, cure at 120 °C for 2 h, and then raise the temperature to 160 °C and cure for 1 h to obtain a high - performance, degradable, recyclable and self - healing epoxy resin (AZH - EP).

[0035] Example 3

[0036] A preparation method of a novel epoxy resin (AZH - EP) includes:

[0037] The epoxy resin prepared in this experiment adopts a stepwise curing method. React isophthalic dimethoxyacetyl hydrazide (1 mmol) and vanillin (1 mmol) at 70 °C for 2 h, then raise the temperature to 90 °C, add bisphenol A epoxy resin monomer (1.5 mmol) and mix evenly to obtain the first mixture; add accelerator - 2 - ethyl - 4 - methylimidazole (1% of the mass of the first mixture) to the first mixture and mix evenly to obtain the second mixture; then place it in a mold, evacuate at 120 °C for 5 min, cure at 120 °C for 2 h, and then raise the temperature to 160 °C and cure for 1 h to obtain a high - performance, degradable, recyclable and self - healing epoxy resin (AZH - EP).

[0038] Example 4

[0039] A preparation method of a novel epoxy resin (AZH - EP) includes:

[0040] The epoxy resin prepared in this experiment adopts a stepwise curing method. React isophthalic dimethoxyacetyl hydrazide (1 mmol) and vanillin (1 mmol) at 70 °C for 2 h, then raise the temperature to 90 °C, add bisphenol A epoxy resin monomer (1.5 mmol) and mix evenly to obtain the first mixture; add accelerator - 2 - ethyl - 4 - methylimidazole (2% of the mass of the first mixture) to the first mixture and mix evenly to obtain the second mixture; then place it in a mold, evacuate at 120 °C for 5 min, cure at 120 °C for 2 h, and then raise the temperature to 160 °C and cure for 1 h to obtain a high - performance, degradable, recyclable and self - healing epoxy resin (AZH - EP).

[0041] Example 5

[0042] A preparation method of a novel epoxy resin (AZH - EP) includes:

[0043] The epoxy resin prepared in this experiment was cured in a stepwise manner. Isophthalic dimethoxyacetyl hydrazide (1 mmol) and vanillin (1 mmol) were reacted at 70 °C for 2 h. After heating to 120 °C, bisphenol A epoxy resin monomer (1.5 mmol) was added and mixed evenly to obtain the first mixture. A promoter, 2-ethyl-4-methylimidazole (1% of the mass of the first mixture), was added to the first mixture and mixed evenly to obtain the second mixture. Subsequently, it was placed in a mold, evacuated at 120 °C for 5 min, cured at 120 °C for 1 h, and then heated to 160 °C and cured for 1 h to obtain a high-performance, degradable, recyclable, and self-healing epoxy resin (AZH-EP).

[0044] Application Example 1

[0045] A preparation method of an epoxy composite material (AZH-EP / CF) includes:

[0046] A prepreg was prepared by pre-impregnation and hot pressing. Carbon fiber T700 was fixed on a Teflon mold, and the mold was placed horizontally in an oven at 120 °C. According to the ratio of Example 3, isophthalic dimethoxyacetyl hydrazide and vanillin were reacted at 70 °C for 2 h, then heated to 120 °C, and bisphenol A epoxy resin monomer was added and mixed evenly to obtain the first mixture. A promoter, 2-ethyl-4-methylimidazole (1% of the mass of the first mixture), was added to the first mixture and mixed evenly to obtain the second mixture. It was poured into the Teflon mold and evacuated in an oven at 120 °C for 5 min. Then, it was hot pressed at 120 °C under a pressure of 1 MPa for 1 h to obtain the prepreg. Before use, all samples were stored in a desiccator. The epoxy composite material (AZH-EP / CF) was obtained by hot pressing 20 layers of CFRP prepreg at 120 °C and a pressure of 1 MPa for 1 h, and then thermally cured at 160 °C in an oven for 2 h.

[0047] Application Example 2

[0048] A preparation method of an epoxy composite material (AZH-EP / CF) includes:

[0049] The prepreg is prepared by means of pre - impregnation and hot pressing. The carbon fiber T300 is fixed on a Teflon mold, and the mold is placed horizontally in an oven at 120 °C. According to the ratio of Example 3, isophthalyl dihydrazide and vanillin are reacted at 70 °C for 2 h, then the temperature is raised to 120 °C, and bisphenol A epoxy resin monomer is added and mixed evenly to obtain the first mixture; a promoter, 2 - ethyl - 4 - methylimidazole (1% of the mass of the first mixture), is added to the first mixture and mixed evenly to obtain the second mixture; the second mixture is poured into the Teflon mold, and after evacuating for 5 min in an oven at 120 °C. It is hot - pressed at 120 °C under a pressure of 1 MPa for 1 h to obtain the prepreg. Before use, all samples are stored in a desiccator. The epoxy composite material (AZH - EP / CF) is obtained by hot - pressing 20 layers of CFRP prepreg at 120 °C and a pressure of 1 MPa for 1 h, and then thermally curing at 160 °C in an oven for 2 h.

[0050] Test Example 1

[0051] Tensile property test

[0052] The tensile properties of the materials are tested using an Instron 5567 universal material testing machine. The high - performance, degradable, recyclable and self - healing epoxy resin dumbbell - shaped splines prepared in Examples 1, 2, and 3 are uniaxially stretched at a tensile rate of 50 mm / min at room temperature, and the stress - strain curves are recorded. Five samples are tested in parallel for each group.

[0053] The mechanical properties of the materials under different epoxy monomer ratios are characterized by tensile property testing ( Figure 1 ), and it can be seen that the best ratio is Example 3, with isophthalyl dihydrazide, vanillin, and bisphenol A epoxy resin monomer (molar ratio: 1:1:1.5). Under this ratio, the tensile strength and Young's modulus of the material are 94.07 ± 7.26 MPa and 2.60 ± 0.21 GPa, respectively.

[0054] Test Example 2

[0055] Dynamic thermomechanical property test

[0056] The loss factor (Tan(Delta)) of the high - performance, degradable, recyclable and self - healing epoxy resin splines prepared in Examples 1, 2, and 3 is measured in tensile mode using a TA Q800 dynamic mechanical thermal analyzer. The test dimensions of the rectangular samples are approximately 0.5 mm (T) × 3 mm (W) × 8 mm (L), the heating rate is 3 °C / min, the measurement range is from room temperature to 200 °C, the strain amplitude value is 0.1%, and the test frequency is 1 Hz.

[0057] The thermal properties of the materials under different epoxy monomer ratios are characterized by dynamic thermomechanical property testing ( Figure 2), it can be seen that the best ratio is Example 3, isophthalic dimethoxyacetyl hydrazide, vanillin, bisphenol A epoxy resin monomer (molar ratio: 1:1:1.5). Under this ratio, the Tg of the material can reach 141 °C.

[0058] Test Example 3

[0059] Interlaminar Shear Strength Test of Epoxy Resin Carbon Fiber Composite

[0060] Taking the epoxy resin carbon fiber composite prepared in Application Example 1 as a sample, the interlaminar shear strength of the composite was tested. Figure 3 is the interlaminar shear strength of the epoxy resin carbon fiber composite. It can be seen that the composite has very excellent interlaminar shear strength, reaching 60.82 MPa.

[0061] Test Example 4

[0062] Recycling Experiment of Epoxy Resin Carbon Fiber Composite

[0063] The epoxy resin carbon fiber composite prepared in Application Example 1 was heated in isophorone diamine at 120 °C for 4 h. Its degradation performance was observed. The experiment found that the composite could be completely degraded under this condition. The degraded resin could achieve closed-loop recycling of the resin by adding monomers. At the same time, the carbon fibers recycled by this method had properties similar to those of the original carbon fibers.

[0064] The description and drawings of the present invention are considered to be illustrative rather than restrictive. Based on the present invention, those skilled in the art can make some substitutions and deformations of some technical features without creative labor according to the disclosed technical content, and all are within the protection scope of the present invention.

Claims

1. A method for preparing a novel epoxy resin, comprising: Reacting isophthalic acid dimethoxy acetohydrazide and aldehyde at 70° C. for 2 hours, heating to 90-120° C., adding bisphenol A epoxy resin monomer and mixing evenly to obtain a first mixture; Adding an accelerator to the first mixture and mixing evenly to obtain a second mixture; The second mixture was placed in a mold, vacuumed at 90-120°C for 5 minutes, and cured by step-by-step temperature ramping to obtain a new epoxy resin named AZH-EP.

2. The preparation method according to claim 1, wherein: Isophthalic acid dimethoxy hydrazide, aldehyde and bisphenol A epoxy resin are added in a molar ratio of 1:1:(1.5-2.5).

3. The preparation method according to claim 1, wherein: The aldehyde is selected from: one or more of vanillin, m-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, o-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, and 4-hydroxy-3-ethoxybenzaldehyde.

4. The preparation method according to claim 1, wherein: The bisphenol A type epoxy resin monomer is selected from one or more of bisphenol A diglycidyl ether BGEBA, epoxy E51, epoxy E44, epoxy E35, epoxy E20, NPES-601, NPES-901, NPES-902, and NPES-903.

5. The preparation method according to claim 1, wherein: The accelerator is selected from: one or more of 2-ethyl-4-methylimidazole, 2-methylimidazole, and 2-ethylimidazole; The mass of the accelerator is 0.5%-2% of the total mass of the first mixture.

6. The preparation method according to claim 1, wherein: The step-by-step temperature-increasing curing comprises: curing at 90-120° C. for 1-2 hours; and then heating to 160° C. for curing for 1-2 hours.

7. A novel epoxy resin obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the novel epoxy resin according to claim 7 in preparing a composite material, wherein: The epoxy composite material is prepared by the following method: The new epoxy resin is compounded with carbon fiber to obtain an epoxy composite material named AZH-EP / CF.

9. An epoxy composite material prepared according to the application of claim 8.

10. Use of the epoxy composite material prepared according to claim 9 in the preparation of electronic equipment, lightweight automobiles, wind turbines and aerospace fields.

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