Crosslinked epoxy resin capable of being reprocessed under condition of being lower than glass-transition temperature as well as preparation method and application of crosslinked epoxy resin

Abstract

The invention provides cross-linked epoxy resin capable of being reprocessed under the condition of being lower than the glass transition temperature as well as a preparation method and application of the cross-linked epoxy resin, and belongs to the technical field of advanced new materials. According to the invention, imine bonds and VU dynamic covalent bonds are respectively introduced into the epoxy resin and the curing agent with specific structures, the epoxy resin glass polymer material with a cross-linked structure is prepared, the lowest relaxation temperature of the glass polymer material is obviously reduced, the relaxation time is obviously shortened, and the service life is prolonged. Reprocessing can be performed under conditions below the glass transition temperature. The method has good application prospects in the fields of material repairability improvement, material reprocessing, material recycling and the like.

Description

Technical Field

[0001] The present invention belongs to the field of advanced new material technologies, and particularly relates to a cross-linked epoxy resin that can be reprocessed under conditions below the glass transition temperature, and a preparation method and use thereof. Background Art

[0002] Epoxy resin is an important thermosetting resin and is widely used in industry and daily life. It has excellent dimensional stability, thermal stability, mechanical strength, creep resistance, electrical insulation and chemical resistance. However, due to the infusible characteristics of epoxy resin, it is difficult to be reprocessed, recycled and reshaped, resulting in the fact that aged, damaged and discarded epoxy resins can only be treated by incineration or landfill, causing environmental pollution and resource waste.

[0003] Vitrimer is a polymer with a reversible covalent cross-linked network, which can realize the reconstruction of the cross-linked network while maintaining the cross-linked structure, and has the dual advantages of thermosetting polymers and thermoplastic polymers. This material not only inherits the good mechanical properties and solvent resistance of traditional thermosetting resins such as epoxy resin, but also exhibits the fluidity and repeat processing performance similar to thermoplastic resins, providing an effective way for the recycling and reuse of cross-linked resins. Epoxy vitrimer combines thermoplasticity and thermosetting properties. It has properties similar to traditional thermosetting epoxy at low temperatures, and exhibits good thermoplasticity at high temperatures, and can be reshaped, welded and recycled multiple times. However, the repair temperature of traditional epoxy vitrimer is much higher than the glass transition temperature; and too high reprocessing temperature will cause chain segment degradation of the material to a certain extent, and harsh repair conditions will limit the application fields of the material. Patent application CN116333268A discloses an epoxy resin obtained by compounding a curing agent containing VU dynamic covalent bonds with E51 type epoxy resin, but its lowest relaxation temperature is 140°C, and the relaxation time at 140°C exceeds 1000 s, and it cannot be reprocessed under conditions below the glass transition temperature.

[0004] Therefore, how to select appropriate means to reduce the temperature barrier for material reprocessing or self-repair and repairability, so that it can be reprocessed under conditions below the glass transition temperature, is of great significance for expanding the material properties and application fields. Summary of the Invention

[0005] The purpose of the present invention is to provide a cross-linked epoxy resin that can be reprocessed under conditions below the glass transition temperature, and a preparation method and use thereof.

[0006] The present invention provides an epoxy resin-based glass polymer material, which is prepared from an epoxy resin containing imine dynamic bonds and a curing agent containing VU dynamic covalent bonds; the mass ratio of the epoxy resin containing imine dynamic bonds to the curing agent containing VU dynamic covalent bonds is 1:0.5 to 5; the imine dynamic bond is The VU dynamic covalent bond is

[0007] Further, the epoxy resin is selected from glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, alicyclic epoxide, aromatic epoxy resin, linear aliphatic epoxide, bisphenol A type epoxy resin, phenolic epoxy resin, polyol glycidyl ether type epoxy resin;

[0008] The mass ratio of the epoxy resin containing imine dynamic bonds to the curing agent containing VU dynamic covalent bonds is 1:1 to 1.2.

[0009] Further, the structure of the epoxy resin containing imine dynamic bonds is:

[0010]

[0011] Further, the epoxy resin containing imine dynamic bonds is prepared from vanillin, p-aminophenol, epichlorohydrin and a phase transfer catalyst; the mass ratio of vanillin, p-aminophenol, epichlorohydrin and the phase transfer catalyst is 1:0.2 to 1.5:10 to 20:0.01 to 0.15;

[0012] The mass ratio of vanillin, p-aminophenol, epichlorohydrin and the phase transfer catalyst is 1:0.5 to 0.9:14 to 17:0.06 to 0.1;

[0013] The phase transfer catalyst is tetrabutylammonium bromide;

[0014] The curing agent containing VU dynamic covalent bonds is prepared from a difunctional amine, tris(2-aminoethyl)amine and EGAA;

[0015] The molar ratio of the difunctional amine, tris(2-aminoethyl)amine and EGAA is 1 to 5:0.1 to 0.5:1;

[0016] The structure of EGAA is

[0017] Further, the molar ratio of the difunctional amine, tris(2-aminoethyl)amine and EGAA is 1 to 2:0.4 to 0.5:1;

[0018] The difunctional amine is selected from isophorone diamine, m-xylenediamine or bis(4-amino-3-methylcyclohexyl)methane;

[0019] The preparation method of the EGAA comprises the following steps: uniformly mixing ethylene glycol and tert-butyl acetoacetate and then heating for reaction to obtain the product; the molar ratio of ethylene glycol to tert-butyl acetoacetate is 1:1 to 5.

[0020] Further, the preparation method of the EGAA comprises the following steps: uniformly mixing ethylene glycol and tert-butyl acetoacetate and then heating for reaction to obtain the product; the molar ratio of ethylene glycol to tert-butyl acetoacetate is 1:1 to 5.

[0021] Preferably, the molar ratio of ethylene glycol to tert-butyl acetoacetate is 1:2.3;

[0022] And / or, the temperature of the heating reaction is 120 to 130 °C, and the reaction time is 1 to 5 h;

[0023] And / or, the product is purified by vacuum pumping after the reaction.

[0024] Further, the preparation method of the epoxy resin containing imine dynamic bonds comprises the following steps:

[0025] (1) Mix vanillin and p-aminophenol and react to obtain an intermediate containing imine dynamic bonds;

[0026] (2) Mix the intermediate, epichlorohydrin and a phase transfer catalyst and react for the first time, and then add alkali for the second reaction to obtain the epoxy resin containing imine dynamic bonds.

[0027] Further, the preparation method of the curing agent containing VU dynamic covalent bonds comprises the following steps:

[0028] (i) Mix a difunctional amine and tris(2-aminoethyl)amine;

[0029] (ii) Add EGAA to the mixture in step (i) and react to obtain the curing agent containing VU dynamic covalent bonds.

[0030] Further, in step (1), the solvent for the reaction is an inorganic solvent; the reaction temperature is 10 to 40 °C, and the time is 2 - 6 hours;

[0031] In step (2), the alkali is an organic base or an inorganic base; the temperature of the first reaction is 50 to 100 °C, and the time is 2 - 6 hours. The condition of the second reaction is to react at 50 to 100 °C for 0.5 - 2 hours first, and then react at 10 to 40 °C for 0.5 - 2 hours.

[0032] Further, in step (1), the solvent for the reaction is water; the reaction temperature is 20 to 30 °C, and the time is 4 hours;

[0033] In step (2), the base is sodium hydroxide; the temperature of the first reaction is 80 °C and the time is 4 hours. The conditions for the second reaction are to react at 80 °C for 1 hour first, and then react at 20 - 30 °C for 1 hour.

[0034] Further, in step (i), after the difunctional amine and tris(2-aminoethyl)amine are mixed, they are preheated at 70 - 90 °C for 1 - 5 minutes;

[0035] And / or, in step (ii), stirring is performed when EGAA is added;

[0036] And / or, after the reaction of adding EGAA in step (ii), the reactant is dried.

[0037] Further, after the difunctional amine and tris(2-aminoethyl)amine are mixed, they are preheated at 80 °C for 3 minutes.

[0038] The present invention also provides a method for preparing the above-mentioned epoxy resin-based glass polymer material, which includes the following steps: mixing the epoxy resin containing imine dynamic bonds and the curing agent containing VU dynamic covalent bonds, and then performing a curing reaction to obtain the product.

[0039] Further, the conditions for the curing reaction are to react at 1 - 10 MPa and 50 - 100 °C for 1 - 4 hours first, and then react at 1 - 10 MPa and 100 - 140 °C for 1 - 4 hours.

[0040] Further, the conditions for the curing reaction are to react at 5 MPa and 80 °C for 2 hours first, and then react at 5 MPa and 120 °C for 2 hours.

[0041] The present invention also provides the use of the above-mentioned epoxy resin-based glass polymer material in the preparation of self-healing materials for aerospace.

[0042] The present invention also provides the use of the above-mentioned epoxy resin-based glass polymer material in the field of reprocessing.

[0043] In the present invention, the difunctional amine refers to a small molecule that simultaneously has two amino (-NH2) functional groups.

[0044] Experimental results show that the present invention uses self-synthesized epoxy resin, and imine bonds and VU dynamic covalent bonds are respectively introduced into the structures of the epoxy resin and the curing agent to prepare an epoxy resin-based glass polymer material. The lowest relaxation temperature of this type of glass polymer material is significantly reduced, and the relaxation time is significantly shortened. It can be reprocessed at a temperature lower than the glass transition temperature and has good application prospects in the preparation of self-healing materials for aerospace.

[0045] Obviously, based on the above content of the present invention, according to the common general technical knowledge and conventional means in the art, without departing from the above basic technical idea of the present invention, various other forms of modifications, substitutions or changes can also be made.

[0046] The following is a further detailed description of the above content of the present invention through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. Brief Description of the Drawings

[0047] Figure 1 Schematic diagram for synthesizing EDT curing agent containing VU dynamic covalent bond (a), chemical shift characterization of EGAA (b), and infrared spectrum changes of EGAA and EDT (c).

[0048] Figure 2 DSC curves of DDEM at different heating rates (a) and fitting results of the starting temperature, peak temperature, and termination temperature of the peak curves at different heating rates (b).

[0049] Figure 3 Stress relaxation test curves of resin systems containing single dynamic exchange bonds (E51-100) (a) and resin systems containing double dynamic exchange bonds (b), and schematic diagrams of the structures of GE-VAN-AP and E51 (c).

[0050] Figure 4 DMA test results of the resin system containing double dynamic exchange bonds before and after being reprocessed twice.

[0051] Figure 5 Infrared spectrum changes of the original sample of the resin system containing double dynamic exchange bonds and after the first and second reprocessing.

[0052] Figure 6 Tensile strength curves of the original sample of the resin system containing double dynamic exchange bonds and after being reprocessed twice. Detailed Description of the Specific Embodiments

[0053] The raw materials and equipment used in the present invention are all known products, obtained by purchasing commercially available products.

[0054] The "room temperature" condition of the present invention is 25 ± 5°C.

[0055] Example 1. Preparation of an epoxy resin system containing double dynamic exchange bonds

[0056] 1. Preparation of an intermediate containing imine dynamic bonds

[0057] 6.08 g (40 mmol) of vanillin and 4.36 g (40 mmol) of p-aminophenol were mixed and added to a round-bottom flask, then 125 mL of water was added, and the mixture was stirred at room temperature for 4 h. After filtration, a yellow powder was collected, washed with water, and then placed in a dryer to dry, obtaining a pale yellow powder (9.32 g), which was named VAN-AP powder. The NMR data of VAN-AP are as follows: 1 H NMR (DMSO-d6, 400 MHz) δ: 9.69 (s, 1H, -OH), 9.44 (s, 1H, -OH), 8.43 (s, 1H, -CH=N-), 7.49 (d, 1H, Ar-H), 7.27 (dd, 1H, Ar-H), 7.10 - 7.13 (m, 2H, Ar-H), 6.86 (d, 1H, Ar-H), 6.75 - 6.79 (m, 2H, Ar-H), 3.84 (s, 3H, -OCH3).

[0058] 2. Preparation of epoxy resin containing imine dynamic bonds

[0059] 9.8 g (40 mmol) of VAN-AP powder was taken and mixed with 100 g (1081 mmol) of epichlorohydrin, added to a round-bottom flask, and then 0.5 g (1.7 mmol) of tetrabutylammonium bromide was added as a phase transfer catalyst. The round-bottom flask was placed in an 80 °C water bath and stirred for 4 h, then 12.5 g of a 50% NaOH aqueous solution by weight was added, and the reaction was continued for 1 h, followed by reacting at room temperature for 1 h. An excess of ethyl acetate was added, and the formed NaCl solid particles were removed by filtration. It was washed three times with deionized water, concentrated, transferred to a vacuum oven, and dehydrated overnight at 60 °C, finally obtaining an epoxy resin containing imine bonds, which was a pale yellow solid and was named GE-VAN-AP resin. The NMR data of GE-VAN-AP resin are as follows: 11H NMR (DMSO-d6, 400 MHz) δ: 8.52 (s, 1H, -CH=N-), 7.56 (d, 1H, Ar-H), 7.39 - 7.41 (dd, 1H, Ar-H), 7.26 - 7.24 (m, 2H, Ar-H), 7.08 - 7.10 (d, 1H, Ar-H), 6.99 - 7.01 (m, 2H, Ar-H), 4.37 - 4.40 (dd, 1H, Ar-H), 4.33 - 4.37 (dd, 1H, Ar-H), 3.87 - 3.92 (dd, 1H, -O-CH2-), 3.86 (s, 3H, -OCH3), 3.83 - 3.87 (dd, 1H, -O-CH2-), 3.34 - 3.39 (m, 2H, -CH-in oxirane), 2.85 - 2.86 (m, 2H, -CH2-in oxirane), 2.71 - 2.73 (m, 2H, -CH2-in oxirane).

[0060] 3. Preparation of ethylene glycol diacetoacetate

[0061] First, ethylene glycol and tert-butyl acetoacetate were mixed evenly in a molar ratio of 1:2.3 and heated to 125 °C for 1 hour. Then, using a circulating water vacuum pump, vacuum extraction was carried out at 0.03 MPa for 3 h to remove the tert-butanol produced by the reaction and promote the forward reaction. Subsequently, the system vacuum was reduced to 0.09 MPa and maintained for 1 h to remove the unreacted ethylene glycol and tert-butyl acetoacetate to ensure the purity of the product. Finally, a light orange product, namely ethylene glycol diacetoacetate (EGAA), was obtained.

[0062] 4. Preparation of curing agent containing VU dynamic covalent bonds

[0063] Weigh 12.93 g (0.0761 mol) of isophorone diamine and 3.17 g (0.0217 mol) of tris(2-aminoethyl)amine in a round-bottom flask. After mixing evenly, place it in an oil bath and heat to 80 °C for preheating for 3 minutes. Then, under the stirring of a magnetic stirrer, slowly add 10 g (0.04347 mol) of EGAA dropwise into the flask, and the total dropping time is 8 minutes. As time goes by, the transparent solution of the amine will gradually turn light yellow. After the dropping is completed, continue stirring for 5 minutes to ensure that the amine and EGAA react fully and are mixed evenly to obtain a mixture containing m-vinylamino ester groups. This curing agent is named EDT curing agent. Then pour the mixture into a petri dish with a diameter of 200 mm, transfer it to a vacuum oven, and keep the vacuum negative pressure at 0.1 MPa at 65 °C for 24 hours to remove the water generated by the reaction. After the water removal is completed, put the curing agent containing VU dynamic bonds into the refrigerator for freezing storage to prevent oxidation. After calculation, the primary amine content in the curing agent is 0.005311 mol / g.

[0064] 5. Preparation of Epoxy Resin System Containing Dual Dynamic Exchange Bonds

[0065] Take 10 g of GE-VAN-AP resin and 11.65 g of EDT curing agent, stir and mix evenly at 80 °C, then transfer to a vacuum oven to remove air bubbles. Then transfer the mixed sample to a flat vulcanizer, pour it into a steel plate mold, heat to 80 °C under a pressure of 5 MPa, keep it for two hours and then heat to 120 °C and keep it for two hours. Demold the sample at high temperature, and then anneal and cool it in a forced-air oven to obtain a flaky sample, which is named resin system containing dual dynamic exchange bonds (Dual dynamic exchange mechanism resin system), abbreviated as DDEM resin.

[0066] The following is the preparation method of the control example.

[0067] Control Example 1. Preparation of Epoxy Resin System Containing Single Dynamic Exchange Bond

[0068] Refer to the method of Example 1, the difference is only that the GE-VAN-AP resin in step 5 is replaced with commercial E51 type epoxy resin (epoxy value is 0.51), and a flaky sample is prepared together with EDT curing agent, which is named resin system containing single dynamic exchange bond, abbreviated as E51-100.

[0069] The following proves the beneficial effects of the present invention through experimental examples.

[0070] Experimental Example 1. Performance Test of Epoxy Resin Containing Dual Dynamic Exchange Bonds at Temperatures Below the Glass Transition Temperature

[0071] 1. Experimental methods

[0072] (1) Dynamic thermomechanical property test (DMA): A Q800 dynamic thermomechanical analyzer produced by TA Instruments, USA, was used. The tensile fixture was selected for testing. The test frequency was 1 Hz, the amplitude was 15 μm, the heating rate was 3 °C / min, and the test temperature range was 0 °C to 200 °C.

[0073] (2) Differential scanning calorimetry (DSC) test: For uncured samples, a differential scanning calorimeter (Mettler Toledo, Switzerland) was used to explore the curing temperature of the curing agent and the resin. The test atmosphere was N2, the test temperature range was 30 - 200 °C, and the heating rates were 5 K / min, 10 K / min, 15 K / min, and 20 K / min respectively. For cured samples, the test temperature range of 30 - 200 °C and the heating rate of 10 K / min were selected to characterize the curing situation and the glass transition temperature of the material.

[0074] (3) Mechanical property test: The tensile property was tested using an Instron universal testing machine according to the standard of GB / T1040 - 2006. The 5B type tensile spline was used for the test size, and the tensile speed was 1 mm / min.

[0075] (4) Remachining experiment: 20 g of the cured sample of Example 1 was put into a crushing mixer and continuously crushed for 10 seconds. The crushed particles were evenly placed into a hot pressing mold and hot pressed at 120 °C and 5 MPa for 30 min, and then the mold was opened after natural cooling. The remachined and hot - pressed repaired sample sheet was cut into the target spline using a cutter. The repair efficiency was calculated by the following formula:

[0076]

[0077] (5) Stress relaxation test: A stress relaxation experiment was tested using an Anton Paar rheometer. A constant shear strain of 1% and a normal force of 5 N were selected.

[0078] 2. Experimental results

[0079] The experimental results ( Figure 1 a - c) show that in this study, EGAA and EDT containing VU dynamic covalent bonds were successfully synthesized. The structure of the VU dynamic covalent bond is as shown in Figure 1 a, the chemical shift characterization of EGAA and the infrared spectrum changes of EGAA and EDT are shown in Figure 1 b and c respectively.

[0080] (1) Study on the curing process of the resin system containing dual dynamic exchange bonds

[0081] Figure 2a shows the DSC curves at different heating rates. It can be seen that at different heating rates, the positions and peak heights of the curves have changed significantly; as the heating rate increases, the DSC exothermic peak as a whole shifts to higher temperatures. Then, the starting temperature, peak temperature, and ending temperature of the peak curves at different heating rates are fitted, and the fitting results are shown in Figure 2 b. The extrapolated intercepts of the fitting linear lines for the three curing temperatures are the reaction temperatures during isothermal curing at a heating rate of 0. Table 1 is the statistical table of the cured temperatures after fitting. Among them, the starting temperature for the curing of the resin system containing double dynamic exchange bonds is approximately 43.08 °C, the peak temperature is 83.69 °C, and the ending temperature of the curing exotherm is 115.77 °C. Therefore, in order to ensure complete curing of the system, the final curing process is determined to be holding at a constant temperature of 80 °C for two hours and then holding at a constant temperature of 120 °C for two hours.

[0082] Table 1. Fitting Table of Curing Temperatures of Resin Containing Double Dynamic Exchange Bonds

[0083]

[0084] (2) Stress Relaxation Study of Resin Systems Containing Different Dynamic Exchange Bonds

[0085] Figure 3 These are the stress relaxation test curves of the resin system containing single dynamic exchange bonds (E51-100) and the resin system containing double dynamic exchange bonds. As Figure 3 shown in a, as the temperature increases, the relaxation curve gradually shifts to the left, and the relaxation time gradually decreases. For the E51-100 system, its relaxation rate gradually becomes faster as the temperature increases, and its relaxation time at 140 °C exceeds 1000 s; compared with E51-100, the relaxation rate of the resin containing double dynamic exchange bonds is significantly increased, and the relaxation time is significantly shortened. The relaxation times at temperatures from 120 °C to 140 °C are all less than 400 s ( Figure 3 b). E51 in the E51-100 system is a common commercial epoxy resin, which does not cure with the VU dynamic bond curing agent and cannot be tested for stress relaxation alone. GE-VAN-AP in the resin system containing double dynamic exchange bonds is a self-synthesized epoxy resin. The difference between the structure of GE-VAN-AP and E51 is that the middle of the GE-VAN-AP structure is an imine bond, while the middle of the E51 structure is a C-C bond ( Figure 3 c). Therefore, it can be proved that the introduction of the imine bond can achieve a faster stress relaxation rate and enable repair at 120 °C.

[0086] (3) Comparison of Various Properties before and after Resin Reprocessing

[0087] Figure 4 These show the DMA test results of the resin containing double dynamic exchange bonds before and after being reprocessed twice. AsFigure 4 As shown, the differences in storage modulus before and after the original sample (Origin), first recycling (Recycle 1), and second recycling (Recycle 2) are relatively small, all around 4000 MPa, indicating that the recycled materials can still maintain a certain degree of rigidity and form a whole. The peak temperature of Tanδ can represent the glass transition temperature of the material. The glass transition temperatures of the original sample, first recycled sample, and second recycled sample are 125.87 °C, 131.65 °C, and 128.63 °C respectively, with relatively small differences among them, all within the range of 125 - 135 °C. At the same time, it can be seen that as the number of recycling times increases, the Tanδ peak gradually decreases and the peak width gradually becomes wider, indicating that the internal friction of the system gradually decreases and the flexibility distribution of molecular chain segments becomes wider. Through the results of DMA testing, it can be found that the samples after multiple recycling can maintain the same storage modulus and glass transition temperature as the original sample, demonstrating the good recycling ability of the samples.

[0088] Figure 5 The infrared spectrum changes and DSC test changes of the original sample of the resin containing double dynamic exchange bonds, and the samples recycled for the first and second times are respectively shown in Figure 5 As shown, for the original sample, the characteristic peak of the generated imine bond (C-N) is at 1650 cm -1 There is no significant peak at 915 cm -1 and its surrounding areas, indicating that the unopened epoxy groups in the system have completely reacted. The significant aromatic ring characteristic peak is at 1500 cm -1 The characteristic peak of -OH generated by epoxy ring opening and the N-H band caused by unreacted -NH2 are above 3000 cm -1 The characteristic peak of the -CH2- chain segment is at 2850 cm -1 to 2900 cm -1 There is no significant difference in the above groups between the original sample and the samples obtained by the first and second recycling, indicating that there is no significant change in the groups before and after multiple recycling.

[0089] Figure 6 The tensile strength curves of the original sample of the resin containing double dynamic exchange bonds and the sample recycled twice are shown. As Figure 6As shown, all the splines exhibit brittle fracture during tensile testing without an obvious yield point. Table 2 summarizes the comparison of different mechanical properties during the tensile process of different splines. The tensile strength of the original sample is approximately 100 MPa, which is much higher than that of ordinary commercial epoxy resins (40 - 70 MPa). After hot pressing treatment, the cured epoxy resin particles can re - fuse into a uniform whole. After the first re - processing, the tensile strength drops to 91.77 MPa, which is 91.47% of the initial tensile strength. After the second re - processing, the tensile strength drops to 75.78 MPa, which is 75.54% of the initial tensile strength. With the increase in the number of re - processing times, both the tensile strength and the elongation at break show a significant downward trend, while the tensile modulus shows a gradually increasing trend. This is mainly because with multiple crushing - re - processing hot pressing processes, there are more defects in the epoxy resin structure. And due to maintaining a high temperature in the air, the thermo - oxidative aging process gradually accumulates, resulting in a gradual decrease in tensile strength and elongation. At the same time, the hot pressing treatment can also be regarded as a post - curing process, which may lead to an increase in cross - link density, thus the modulus shows an increasing trend. However, the resin can still reach 75.78 MPa after two re - processing cycles, still comparable to the tensile strength of ordinary commercial epoxy resins. This represents that under the action of the dual dynamic exchange mechanism, the material achieves good re - processing ability; and the enhancement effect of mechanical properties brought by imine bonds is very obvious; the effect of simultaneously improving the mechanical strength and dynamic exchange ability of the material is realized.

[0090] Table 2. Comparison of mechanical properties such as tensile strength of different splines

[0091]

[0092] As can be seen from the above experimental results, the lowest relaxation temperature of the resin system (E51 - 100) with single - dynamic exchange bonds in Comparative Example 1 is 140 °C, and the relaxation time at 140 °C exceeds 1000 s. Compared with E51 - 100, the lowest relaxation temperature of the resin with dual - dynamic exchange bonds incorporating imine bonds and VU dynamic covalent bonds in Example 1 of the present invention is 95 °C, and the relaxation time at temperatures from 95 °C to 120 °C is less than 10 s. That is to say, compared with the resin system with single - dynamic exchange bonds in Comparative Example 1, the lowest relaxation temperature of the resin system with dual - dynamic exchange bonds of the present invention is significantly reduced, and the relaxation time is significantly shortened.

[0093] The glass transition temperature of the resin system with dual - dynamic exchange bonds of the present invention is 125.87 °C. This resin system can be re - processed at temperatures below the glass transition temperature, and the re - processed samples still retain good mechanical properties.

[0094] In summary, the present invention provides a crosslinked epoxy resin that can be reprocessed under conditions below the glass transition temperature, as well as a preparation method and use thereof. In the epoxy resin and curing agent with specific structures of the present invention, imine bonds and VU dynamic covalent bonds are respectively introduced to prepare a crosslinked epoxy resin-based glass polymer material. The lowest relaxation temperature of this type of glass polymer material is significantly reduced, and the relaxation time is significantly shortened, enabling reprocessing under conditions below the glass transition temperature. It has good application prospects in the fields of improving material reparability, material reprocessing, and material recycling and reuse.

Claims

1. An epoxy resin-based glass polymer material, characterized in that, The invention is prepared from epoxy resin containing imine dynamic bonds and curing agent containing VU dynamic covalent bonds as raw materials; the mass ratio of the epoxy resin containing imine dynamic bonds and the curing agent containing VU dynamic covalent bonds is 1:0.5-5; the imine dynamic bonds are The VU dynamic covalent bond is 2. The epoxy resin-based glass polymer material according to claim 1, wherein The epoxy resin is selected from glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, alicyclic epoxides, aromatic epoxy resins, linear aliphatic epoxides, bisphenol A type epoxy resins, phenolic epoxy resins, and polyol glycidyl ether type epoxy resins; The mass ratio of the epoxy resin containing imine dynamic bonds to the curing agent containing VU dynamic covalent bonds is 1:1 to 1.

2.

3. The epoxy resin-based glass polymer material according to claim 1, wherein The structure of the epoxy resin containing imine dynamic bonds is: The curing agent containing VU dynamic covalent bonds is prepared from a difunctional amine, tris(2-aminoethyl)amine, and EGAA as raw materials; The molar ratio of the difunctional amine, tris(2-aminoethyl)amine, and EGAA is 1 to 5:0.1 to 0.5:1; The structure of the EGAA is 4. The epoxy resin-based glass polymer material according to claim 3, wherein, The molar ratio of the difunctional amine, tris(2-aminoethyl)amine, and EGAA is 1 to 2:0.4 to 0.5:1; The difunctional amine is selected from isophorone diamine, m-xylene diamine, or bis(4-amino-3-methylcyclohexyl)methane.

5. The epoxy resin-based glass polymer material according to claim 1, wherein The preparation method of the curing agent containing VU dynamic covalent bonds includes the following steps: (i) Mix the difunctional amine and tris(2-aminoethyl)amine; (ii) Add EGAA to the mixture in step (i) and react to obtain the curing agent containing VU dynamic covalent bonds.

6. The epoxy resin-based glass polymer material according to claim 5, wherein In step (i), after the difunctional amine and tris(2-aminoethyl)amine are mixed, they are preheated at 70 to 90 °C for 1 to 5 minutes; and / or, in step (ii), stirring is carried out when adding EGAA; and / or, in step (ii), after adding EGAA and reacting, the reactant is dried.

7. A method for preparing the epoxy resin-based glass polymer material according to any one of claims 1-6, characterized in that, The method includes the following steps: Mix the epoxy resin containing imine dynamic bonds and the curing agent containing VU dynamic covalent bonds, and then carry out a curing reaction to obtain the product.

8. The method according to claim 7, wherein The conditions of the curing reaction are to react at 1-10 MPa and 50 to 100 °C for 1-4 hours, and then react at 1-10 MPa and 100 to 140 °C for 1-4 hours.

9. Use of the epoxy resin-based glass polymer material according to any one of claims 1-6 in the preparation of a self-healing material for aerospace.

10. Use of the epoxy resin-based glass polymer material according to any one of claims 1-6 in the field of reprocessing.

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