Microcapsule type self-repairing epoxy resin material with high thermal stability and preparation method thereof

Abstract

The invention relates to a microcapsule type self-repairing epoxy resin material with high thermal stability and a preparation method thereof, and belongs to the technical field of high polymer materials. According to the invention, a double-component microcapsule with extremely high thermal stability, namely an epoxy resin microcapsule with a core liquid containing BADGE and an amine microcapsule with a core liquid containing PEI, are added into imidazole cured epoxy resin to form the self-repairing imidazole cured epoxy resin material, so that the resin material can be self-repaired at a service temperature (80-100 DEG C) after being damaged; according to the invention, the two microcapsules are extremely low in loss in the curing process of the imidazole curing epoxy resin, have excellent survival performance, basically have no loss at long-term service temperature, and can ensure the self-repairing function of the resin material; the particle sizes of the two microcapsules are 50-100 microns, so that the two microcapsules can be conveniently mixed and constructed with imidazole cured epoxy resin, and the two microcapsules are very good in thermal stability and are compatible with a curing process of the imidazole cured epoxy resin.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a microcapsule-type self-healing epoxy resin material with high thermal stability and its preparation method. Background Technology

[0002] Dry-type reactors, as key equipment in power systems, typically employ fiber-reinforced epoxy resin (FRP) composites for their insulation encapsulation to enhance mechanical strength and electrical insulation performance. However, in actual operation, the encapsulation material is subjected to long-term environmental factors such as mechanical vibration, thermal stress, and ultraviolet radiation, which can easily lead to microcracks or even macroscopic cracking. These cracks not only reduce the mechanical properties of the material but may also propagate, causing insulation failure and severely impacting the safe service life of the reactor. Therefore, improving the crack propagation resistance of epoxy resin composites and endowing them with self-repair capabilities has become a research hotspot in the field of power equipment materials in recent years.

[0003] Self-healing materials, as an emerging functional material, offer a new approach to solving this problem. Their core principle involves pre-introducing a repair agent carrier (such as microcapsules or microvessels) within the material. When the material is damaged, the repair agent is released and reacts with the matrix or another component, achieving automatic crack repair. In epoxy resin-based composites, microcapsule-based self-healing systems have attracted considerable attention due to their ease of preparation and high repair efficiency. Currently, a typical design involves dispersing two types of microcapsules within an epoxy resin matrix, encapsulating epoxy resin (such as bisphenol F diglycidyl ether, BFDGE) and an amine curing agent (such as polyetheramine JEFFAMINE T403), respectively. When the crack propagates to the microcapsule, the repair agent is released and reacts on the crack surface, forming a cross-linked network, thereby achieving self-healing functionality.

[0004] However, applying current self-healing technologies to the epoxy resin encapsulation layers of dry-type reactors faces the following key challenges. First, the high-temperature curing adaptability of the repair agent system is insufficient. Dry-type reactor encapsulation materials typically use imidazole curing agents for high-temperature curing (above 120°C). If the thermal stability of the repair agent system is insufficient, volatilization during curing can lead to a significant reduction in repair efficiency. Second, the stability of the repair agent system at the reactor's service temperature is insufficient. During reactor operation, due to electromagnetic losses and ambient temperature, the encapsulation layer is constantly exposed to a high-temperature environment of 80-100°C. Currently common repair agent systems are prone to oxidative degradation or diffusion loss at this temperature, leading to microcapsule failure and preventing long-term stable self-healing functionality. Furthermore, existing microencapsulation technologies have limitations. Traditional microcapsule preparation methods (such as in-situ polymerization and solvent evaporation) face problems of low encapsulation efficiency and high wall material permeability when encapsulating repair agents at high temperatures, making it difficult to meet the requirements of reactor encapsulation materials for long-term stable storage of the repair agent.

[0005] As can be seen from the above, there is still a lack of microencapsulated self-healing epoxy resin systems that can simultaneously satisfy high-temperature curing compatibility, long-term service stability, and efficient self-healing performance. Therefore, developing a microencapsulation technology based on a high thermal stability repair agent and combining it with an imidazole-cured epoxy resin matrix has become a key technological breakthrough for improving the reliability of dry reactor encapsulation materials. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a microcapsule-type self-healing epoxy resin material with high thermal stability and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a microcapsule-type self-healing epoxy resin material with high thermal stability, which is formed by mixing and curing epoxy resin monomers, imidazole curing agent, epoxy resin microcapsules and amine microcapsules. The epoxy resin microcapsules include a capsule wall and an epoxy resin core liquid, wherein the epoxy resin core liquid contains bisphenol A bisglycidyl ether (BADGE); the amine microcapsules include a capsule wall and an amine core liquid, wherein the amine core liquid contains tetraethylenepentamine (TEPA), polyethyleneimine (PEI) and isophorone diamine (IPDA). The molecular weight of the polyethyleneimine (PEI) is 1000~2000 Da; The total amount of epoxy resin microcapsules and amine microcapsules in the microcapsule-type self-healing epoxy resin material is 5% to 20% by mass.

[0008] This invention utilizes epoxy resin microcapsules with a core fluid containing BADGE and amine microcapsules with a core fluid containing PEI to prepare microcapsule-type self-healing epoxy resin materials. Both types of microcapsules exhibit extremely high thermal stability and show minimal loss during the curing process of imidazole-cured epoxy resin. In the curing process of the commercially available imidazole-cured epoxy resin used in this invention (curing first at 120°C for 4 hours, then at 140°C for 5 hours), only about 5-6 wt% is lost, demonstrating excellent survival performance. After damage to the imidazole-cured epoxy resin, the damage can be self-repaired at the service temperature of the imidazole-cured epoxy resin (approximately 80-100°C), realizing the self-healing function of the imidazole-cured epoxy resin. The core fluid of the amine microcapsules in this invention must simultaneously contain tetraethylenepentamine (TEPA), polyethyleneimine (PEI), and isophorone diamine (IPDA), with both TEPA and IPDA being indispensable. The role of IPDA and TEPA is to assist PEI microcapsules in forming polyurea capsule walls; they have different functions. During the formation and growth of amine microcapsules, polyamines with lower molecular weight and viscosity exhibit faster diffusion rates, making them more readily diffused from microdroplets across the interface to react with HMDI. IPDA and TEPA have lower molecular weights (IPDA 170 g / mol, TEPA 189 g / mol) and lower viscosity (IPDA approximately 15 mPa·s, TEPA approximately 30 mPa·s at room temperature) compared to PEI with a molecular weight of 1800. The synergistic effect of IPDA and TEPA allows for better microcapsule wall growth and results in microcapsules with lower impurity content. A lack of IPDA leads to thinner microcapsule walls, preventing the formation of dry, dispersed amine microcapsules; a lack of TEPA results in the formation of polyurea impurities, increasing the impurity content within the microcapsules.

[0009] Meanwhile, the molecular weight of polyethyleneimine (PEI) used in this invention also needs to meet a specific range; too high or too low a molecular weight will affect the self-healing performance of the microcapsule-type self-healing epoxy resin material.

[0010] Compared with epoxy resin microcapsules containing BFDGE in the core liquid and amine microcapsules containing JEFFAMINE T403 in the core liquid, the microcapsule-type self-healing epoxy resin material prepared by the present invention using epoxy resin microcapsules containing BFDGE in the core liquid and amine microcapsules containing PEI in the core liquid has higher thermal stability.

[0011] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the mass ratio of epoxy resin microcapsules to amine microcapsules in the microcapsule-type self-healing epoxy resin material is 1:2 to 2:1.

[0012] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the epoxy resin microcapsules have a particle size of 50~100μm; the amine microcapsules have a particle size of 50~100μm.

[0013] As a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the epoxy resin microcapsules have a particle size of 70~100μm; the amine microcapsules have a particle size of 70~100μm.

[0014] In a preferred embodiment of the microencapsulated self-healing epoxy resin material of the present invention, the total amount of epoxy resin microcapsules and amine microcapsules constitutes 10% to 20% of the mass percentage of the microencapsulated self-healing epoxy resin material. Within this content range, the repair efficiency of the microencapsulated self-healing epoxy resin material is higher.

[0015] In a preferred embodiment of the microencapsulated self-healing epoxy resin material of the present invention, the total amount of epoxy resin microcapsules and amine microcapsules constitutes 15% to 20% of the mass percentage of the microencapsulated self-healing epoxy resin material. Within this content range, the repair efficiency of the microencapsulated self-healing epoxy resin material is higher.

[0016] In a preferred embodiment of the microencapsulated self-healing epoxy resin material of the present invention, the total amount of epoxy resin microcapsules and amine microcapsules constitutes 15% by mass in the microencapsulated self-healing epoxy resin material. At this content, the microencapsulated self-healing epoxy resin material exhibits the highest repair efficiency.

[0017] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the epoxy resin monomer is a bisphenol A type epoxy resin, and the bisphenol A type epoxy resin is GELR-128.

[0018] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the imidazole curing agent is QS-812.

[0019] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the capsule walls of both the epoxy resin microcapsules and the amine microcapsules are composed of polyurea. The capsule walls of both the epoxy resin microcapsules (BADGE microcapsules) and the amine microcapsules (PEI microcapsules) are composed of polyurea, possessing a certain strength and providing good support for the microcapsules. Furthermore, after the curing process, the cured resin in the capsule walls and around the microcapsules inhibits the evaporation of the core liquid.

[0020] In a preferred embodiment of the microencapsulated self-healing epoxy resin material of the present invention, the epoxy resin core liquid further contains a diluent, wherein the diluent is n-butyl glycidyl ether (BGE); the mass ratio of tetraethylenepentamine (TEPA), polyethyleneimine (PEI), and isophorone diamine (IPDA) in the amine core liquid is 1~2:6~8:1~2. Preferably, the mass ratio of tetraethylenepentamine (TEPA), polyethyleneimine (PEI), and isophorone diamine (IPDA) in the amine core liquid is 2:7:1.

[0021] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the molecular weight of the polyethyleneimine (PEI) is 1800 Da.

[0022] In a preferred embodiment of the microcapsule-type self-healing epoxy resin material of the present invention, the mass ratio of the epoxy resin monomer to the imidazole curing agent is 100:13.5.

[0023] This invention employs electrostatic spray-interfacial polymerization microencapsulation technology to prepare epoxy resin microcapsules and amine microcapsules.

[0024] Secondly, the present invention provides a method for preparing the above-mentioned microcapsule-type self-healing epoxy resin material, which involves mixing epoxy resin monomer, imidazole curing agent, epoxy resin microcapsules and amine microcapsules, and then curing them to obtain the material.

[0025] As a preferred embodiment of the preparation method of the present invention, the curing procedure is as follows: first, cure at 50℃~70℃ for 1h~3h, then cure at 90℃~110℃ for 1h~3h, then cure at 110℃~130℃ for 3h~5h, and finally cure at 140℃~160℃ for 4h~6h.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention incorporates highly thermally stable two-component microcapsules into imidazole-cured epoxy resin: epoxy resin microcapsules with a core containing BADGE and amine microcapsules with a core containing PEI, forming a self-healing imidazole-cured epoxy resin material. This allows the resin material to self-repair at its service temperature (approximately 80-100°C) after damage, thus endowing the imidazole-cured epoxy resin with self-healing capabilities. The two types of microcapsules used in this invention exhibit minimal loss during the curing process of the imidazole-cured epoxy resin, demonstrating excellent survival performance. They show virtually no loss at the long-term service temperature (approximately 80-100°C), ensuring the self-healing function of the imidazole-cured epoxy resin. Both types of microcapsules have a particle size of 50-100 μm, facilitating mixing and application with the imidazole-cured epoxy resin. The two types of microcapsules exhibit excellent thermal stability and are compatible with the curing process of the imidazole-cured epoxy resin, essentially not affecting other properties of the resin. Attached Figure Description

[0027] Figure 1 To demonstrate the thermal stability of different repair agents in Test Example 1 of this invention at the molding temperature of imidazole-cured epoxy resin, a represents the BADGE and PEI repair agent system, and b represents the BFDGE and T403 repair agent system. Figure 2 The force-displacement curve of the TDCB pure imidazole cured epoxy resin material sample from Comparative Example 1 in Test Example 2 of this invention; Figure 3 The results of the repair efficiency of BADGE and PEI mixed in different stoichiometric ratios on pure imidazole-cured epoxy resin materials in Test Example 2 of this invention; Figure 4 The force-displacement curve of the TDCB microcapsule-type self-healing epoxy resin material sample in Example 1 of Test Example 2 of this invention; Figure 5 The crack fracture surfaces of the microcapsule-type self-healing epoxy resin material in Example 1 of Test Example 2 of the present invention and the crack fracture surfaces of the pure imidazole-cured epoxy resin material in Comparative Example 1 are shown, where a represents Example 1 and b represents Comparative Example 1. Figure 6 The images show SEM images of epoxy resin microcapsules and amine microcapsules in Example 1 of Test Example 3 of the present invention, where a and c represent epoxy resin microcapsules, b and d represent amine microcapsules, and c and d represent the shell-core structure of the microcapsules. Figure 7 The self-healing efficiency of the microcapsule-type self-healing epoxy resin material in Example 1 of Test Example 4 of the present invention changes with time after treatment at 100°C. Figure 8 The self-healing efficiency of the microcapsule-type self-healing epoxy resin material in Comparative Example 6 of Test Example 4 of this invention changes with time after treatment at 100°C. Detailed Implementation

[0028] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0029] Surfactant Arlacel P135 (trade name): purchased from Croda, UK; Epolam 5015 (product name): Purchased from French company Epolam Technologies; Hardener 5014 (product name): Purchased from Acson Technologies, France; GELR-128 (trade name): Hongchang Electronic Materials Co., Ltd.; QS-812 (Product Name): Beijing Jindaoqishi Materials Technology Co., Ltd.; Polyethyleneimine (PEI): molecular weights of 1800 Da, 600 Da, and 5000 Da, manufactured by Shanghai Maclean Biochemical Technology Co., Ltd. JEFFAMINE T403 (product name): Huntsman Corporation, USA.

[0030] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.

[0031] Example 1 An embodiment of the microencapsulated self-healing epoxy resin material of the present invention is formed by mixing and curing epoxy resin monomers, imidazole curing agent, epoxy resin microcapsules and amine microcapsules. The epoxy resin microcapsules include a capsule wall and an epoxy resin core liquid, wherein the epoxy resin core liquid contains bisphenol A bisglycidyl ether (BADGE). The amine microcapsules include a capsule wall and an amine core liquid, wherein the amine core liquid contains tetraethylenepentamine (TEPA), polyethyleneimine (PEI) and isophorone diamine (IPDA). The preparation method of microencapsulated self-healing epoxy resin material includes the following steps: (1) Mix 90 parts of bisphenol A diglycidyl ether (BADGE) with 10 parts of reactive diluent n-butyl glycidyl ether (BGE) to obtain an epoxy resin solution (A10B solution); mix 95 parts of the obtained A10B solution with 5 parts of 4,4-dicyclohexylmethane diisocyanate (HMDI) to obtain an epoxy resin core solution to be coated; load the obtained epoxy resin core solution into a syringe and inject at 4.0... The core liquid microdroplets 1 were extruded at a rate of mL / h and atomized under a static voltage of 22kV to obtain core liquid microdroplets 1. The obtained core liquid microdroplets 1 were received using reaction solution 1 (1.0g sodium dodecyl sulfonate and 12.0g diethylenetriamine dissolved in 100.0mL deionized water to obtain reaction solution 1) to obtain nascent microcapsules containing epoxy resin. The mixture of the obtained nascent microcapsules containing epoxy resin and reaction solution 1 was reacted at 90℃ for 10h. The microcapsules were collected, washed with water, filtered, and dried at room temperature to obtain epoxy resin microcapsules with a particle size of 70μm.

[0032] (2) 20 parts of tetraethylenepentamine (TEPA) were mixed with 70 parts of polyethyleneimine (PEI) with a molecular weight of 1800 Da and 10 parts of isophorone diamine (IPDA) to obtain an amine core liquid to be encapsulated; the obtained amine core liquid was loaded into a syringe and extruded at a rate of 10.0 mL / h, and atomized under a static voltage of 20 kV to form core liquid microdroplets 2. The obtained core liquid microdroplets 2 were received by reaction solution 2 (150 mL of decahydronaphthalene, 3 g of surfactant Arlacel P135, 0.15 g of accelerator triethylenediamine and 18 g of HMDI were mixed to obtain reaction solution 2) to obtain PEI-containing nascent microcapsules; the mixture of the obtained PEI-containing nascent microcapsules and reaction solution 2 was reacted at 90 °C for 3 h, the microcapsules were collected and washed with cyclohexane, filtered, and dried at room temperature to obtain amine microcapsules with a particle size of 70 μm.

[0033] (3) Epoxy resin Epolam 5015 and curing agent Hardener 5014 were mixed at a mass ratio of 100:34 and cured to prepare the outer frame of TDCB sample. The curing program was to cure at room temperature (25℃) for 24h. 1.0 g of epoxy resin microcapsules obtained in step (1) and 1.0 g of amine microcapsules obtained in step (2) were mixed to obtain a microcapsule mixture. The obtained microcapsule mixture was added to a mixture of 18.0 g epoxy resin monomer GELR-128 and imidazole curing agent QS-812 (mass ratio of GELR-128 to QS-812 is 100:13.5), mixed to obtain a liquid mixture, and added to the test chamber of the TDCB sample outer frame. The mixture was cured with a step temperature program of 60℃ for 2h, 100℃ for 2h, 120℃ for 4h, and 140℃ for 5h to obtain a microcapsule-type self-healing epoxy resin material.

[0034] Example 2-3 Two embodiments of the microcapsule-type self-healing epoxy resin material of the present invention are given. The difference between Embodiments 2-3 and Embodiment 1 is only the particle size of the microcapsules. Specifically, Example 2: Compared with Example 1, the epoxy resin microcapsules and amine microcapsules with a particle size of 70 μm in Example 1 were replaced with epoxy resin microcapsules and amine microcapsules with a particle size of 100 μm to prepare a microcapsule-type self-healing epoxy resin material. Example 3: Compared with Example 1, the epoxy resin microcapsules and amine microcapsules with a particle size of 70 μm in Example 1 were replaced with epoxy resin microcapsules and amine microcapsules with a particle size of 50 μm to prepare a microcapsule-type self-healing epoxy resin material.

[0035] Examples 4-6 The present invention provides three embodiments of the microcapsule-type self-healing epoxy resin material. Embodiments 4-6 differ from Embodiment 1 only in the mass concentration of the microcapsules in the adhesive mixture in step (3) (the mass ratio of the two types of microcapsules in the microcapsule mixture remains 1:1). Specifically, Example 4: Compared with Example 1, the mass concentration of microcapsules in the adhesive mixture in step (3) of Example 1 was replaced by 5 wt% instead of 10 wt%, and microcapsule-type self-healing epoxy resin material was prepared; Example 5: Compared with Example 1, the mass concentration of microcapsules in the adhesive mixture in step (3) of Example 1 was replaced by 15wt% instead of 10wt%, and a microcapsule-type self-healing epoxy resin material was prepared. Example 6: Compared with Example 1, the mass concentration of microcapsules in the adhesive mixture in step (3) of Example 1 was replaced by 20wt% instead of 10wt%, and microcapsule-type self-healing epoxy resin material was prepared.

[0036] Comparative Example 1 This invention provides a comparative example of a microcapsule-type self-healing epoxy resin material. The difference between this comparative example and Example 1 is that the epoxy resin material does not contain microcapsules and is formed by mixing and curing epoxy resin monomers and imidazole curing agents.

[0037] The preparation method of the epoxy resin material in this comparative example is as follows: epoxy resin Epolam 5015 and curing agent Hardener 5014 are mixed at a mass ratio of 100:34 and cured to prepare the outer frame of the TDCB sample. The curing program is to cure at room temperature (25℃) for 24 hours. 18.0g of epoxy resin monomer GELR-128 and imidazole curing agent QS-812 (mass ratio of GELR-128 to QS-812 is 100:13.5) are mixed to obtain a glue mixture, which is then added to the test chamber of the TDCB sample outer frame and cured with a step temperature program of 60℃ for 2 hours, 100℃ for 2 hours, 120℃ for 4 hours, and 140℃ for 5 hours to obtain the epoxy resin material.

[0038] Comparative Examples 2-3 The two comparative examples of the microcapsule-type self-healing epoxy resin materials of the present invention, the microcapsule-type self-healing epoxy resin materials of Comparative Examples 2-3, differ from those of Example 1 only in the molecular weight of the polyethyleneimine (PEI) used to prepare the amine microcapsules in step (2). Specifically, Comparative Example 2: Compared with Example 1, the molecular weight of polyethyleneimine (PEI) used to prepare amine microcapsules in step (2) of Example 1 was adjusted from 1800 to 600 to obtain amine microcapsules, and further microcapsule-type self-healing epoxy resin material was obtained. Comparative Example 3: Compared with Example 1, the molecular weight of polyethyleneimine (PEI) used to prepare amine microcapsules in step (2) of Example 1 was adjusted from 1800 to 5000 to obtain amine microcapsules, and further microcapsule-type self-healing epoxy resin material was obtained.

[0039] Comparative Example 4-5 The two comparative examples of the microcapsule-type self-healing epoxy resin material of the present invention, the microcapsule-type self-healing epoxy resin materials of Comparative Examples 4-5, differ from those of Example 1 only in the composition of the amine core liquid to be encapsulated in step (2) of preparing the amine microcapsules. Specifically, Comparative Example 4: Compared with Example 1, the amine core liquid to be encapsulated in step (2) of Example 1 (20 parts tetraethylenepentamine (TEPA) mixed with 70 parts polyethyleneimine (PEI) with a molecular weight of 1800 and 10 parts isophorone diamine (IPDA)) was adjusted to an amine core liquid to be encapsulated without IPDA (30 parts TEPA and 70 parts PEI with a molecular weight of 1800). Although TEPA diffuses faster than PEI, it is still slower, resulting in a slow growth rate of the capsule wall. In addition, since the functionality (5) of TEPA is higher than that of IPDA (2), the cross-linking density of the produced capsule wall is high, which makes it difficult for amine molecules to diffuse. This results in a thinner capsule wall and makes it impossible to form dry and dispersed amine microcapsules, thus failing to obtain microcapsule-type self-healing epoxy resin material. Comparative Example 5: Compared with Example 1, the amine core liquid to be encapsulated in step (2) of Example 1 (20 parts tetraethylenepentamine (TEPA) mixed with 70 parts polyethyleneimine (PEI) with a molecular weight of 1800 and 10 parts isophorone diamine (IPDA)) was adjusted to a TEPA-free amine core liquid to be encapsulated (30 parts IPDA mixed with 70 parts PEI with a molecular weight of 1800). Although IPDA can diffuse rapidly through the interface and react with HMDI, due to its low functionality (2), the crosslinking density of the resulting microcapsule wall is low, and the strength and sealing performance of the microcapsules are low, resulting in poor performance of the synthesized amine microcapsules; in addition, because IPDA can diffuse rapidly through the interface, it is easy to react with HMDI in the reaction solution, eventually forming polyurea impurities, which affects the quality of the amine microcapsules. Therefore, epoxy resin materials were not further prepared.

[0040] Comparative Example 6 This invention provides a comparative example of a microcapsule-type self-healing epoxy resin material. The only difference between this comparative example and Example 1 is the microcapsules. In this comparative example, the epoxy resin microcapsules (microcapsules containing BADGE) of Example 1 are replaced with microcapsules containing BFDGE. At the same time, the amine microcapsules (microcapsules containing PEI) of Example 1 are replaced with microcapsules containing T4O3. The microcapsules containing BFDGE and the microcapsules containing T4O3 are prepared according to the method described in CN120399199A.

[0041] Comparative Example 7 An embodiment of the microcapsule-type self-healing epoxy resin material of the present invention is shown. The only difference between this comparative example and Example 1 is the mass concentration of microcapsules in the adhesive mixture in step (3) (the mass ratio of the two types of microcapsules in the microcapsule mixture is still 1:1). Compared with Example 1, this comparative example replaces the mass concentration of microcapsules in the adhesive mixture in step (3) of Example 1, which was 10wt%, with 2.5wt%, and prepares the microcapsule-type self-healing epoxy resin material.

[0042] Test Example 1 In Comparative Example 1, a crack 8-10 mm long was pre-fabricated in the test chamber of the TDCB sample of pure imidazole-cured epoxy resin. Pure bisphenol A diglycidyl ether (BADGE), pure bisphenol F diglycidyl ether (BFDGE), pure polyethyleneimine (PEI) with a molecular weight of 1800, and pure polyether polyamine (JEFFAMINE T403) were used as repair agents, and were manually injected into the crack for repair. Thermogravimetric analysis (TGA) was used to study the thermal stability of different repair agents during the molding process of imidazole-cured epoxy resin. The TGA temperature program was set to 120℃ for 4 h and 140℃ for 5 h. The mass loss of the four repair agents during the heating process was analyzed, and curves showing the change in the mass fraction of the repair agent as a function of temperature were plotted.

[0043] Thermal stability of different repair agents at the molding temperature of imidazole-cured epoxy resin, such as Figure 1As shown, a represents the BADGE and PEI repair agent system, and b represents the BFDGE and T403 repair agent system. The results show that during the heating process at 120℃ for 4 hours and 140℃ for 5 hours, the repair agent BADGE only lost about 5.7 wt%, and PEI only lost about 6.0 wt%. In contrast, the epoxy repair agent bisphenol F diglycidyl ether (BFDGE) and the amine repair agent polyether polyamine JEFFAMINE T403, which are most commonly used in existing literature based on microencapsulated epoxy-amine chemistry self-healing systems, lost about 14 wt% of BFDGE and about 53 wt% of JEFFAMINE T403 under the same stepped heating program. Therefore, the epoxy-amine repair agent system composed of BADGE and PEI has significantly higher thermal stability, and the self-healing material prepared by microencapsulation of BFDGE will also have higher thermal stability.

[0044] Since BADGE and PEI are very stable at 60℃ and 100℃, and the full curing time of imidazole-cured epoxy resin is too long, the above TGA only characterizes the high-temperature stage of the curing process, namely 120℃ for 4h and 140℃ for 5h.

[0045] Test Example 2 1. A crack 8-10 mm long was pre-fabricated in the test groove of the TDCB samples made of microencapsulated self-healing epoxy resin material in Example 1 and pure imidazole-cured epoxy resin material in Comparative Example 1. Then, the samples were fixed using a universal testing machine, and the samples were pulled apart along the pre-fabricated crack at a loading rate of 1 mm / min (initial fracture). The samples were then cured in a constant temperature and humidity chamber at 80°C for 48 h, and then pulled apart again using the same loading rate using a universal testing machine (secondary fracture after repair). The force-displacement curves during the test were recorded, and the self-healing efficiency based on fracture toughness repair was calculated by taking the highest point of the curve.

[0046] The force-displacement curve of the TDCB sample of pure imidazole cured epoxy resin material in Comparative Example 1 is shown below. Figure 2 As shown in the figure, the results indicate that the pure imidazole-cured epoxy resin material in Comparative Example 1 exhibited absolutely no repair behavior.

[0047] After premixing BADGE and PEI at different stoichiometric ratios, the mixture was manually injected in sufficient quantity into the cracked surface of the imidazole-cured epoxy resin TDCB sample. The repair efficiency was then tested after 48 hours at the service temperature (80℃) of the resin. Repair efficiency (%) = (peak force of the force-displacement curve at the time of re-fracture after repair / peak force of the force-displacement curve at the time of initial fracture) * 100%.

[0048] The repair efficiency of BADGE and PEI mixed in different stoichiometric ratios on pure imidazole-cured epoxy resin materials is as follows: Figure 3As shown, the results indicate that a stoichiometric ratio of BADGE to PEI of 1:0.08~0.28 corresponds to a repair efficiency of over 145.29%, with a maximum of 179.93%. This demonstrates that the combined use of BADGE and PEI as repair agents can significantly improve the repair efficiency of imidazole-cured epoxy resin materials.

[0049] Example 1: The force-displacement curve of the microencapsulated self-healing epoxy resin material TDCB sample is shown below. Figure 4 As shown in the figure, the results indicate that the microcapsule-type self-healing epoxy resin material has excellent self-healing properties, with a self-healing efficiency of 84%.

[0050] 2. Observe the crack cross-section of the epoxy resin material. Example 1: Crack fracture surface of microencapsulated self-healing epoxy resin material after self-healing, and Comparative Example 1: Crack fracture surface of pure imidazole cured epoxy resin material, as shown in the figures. Figure 5 As shown, where a represents Example 1 and b represents Comparative Example 1, the results show that the cracked surface of pure imidazole-cured epoxy resin is very smooth, while the microcapsule-containing imidazole-cured epoxy resin has cured repair agent. These cured repair agents can bond the cracked surfaces together, thereby giving the imidazole-cured epoxy resin a self-healing function.

[0051] The repair efficiency of epoxy resin materials in other embodiments and comparative examples was also tested in this invention. The repair efficiency of epoxy resin materials in Examples 1-6 and Comparative Examples 1-3 and 6-7 is shown in Table 1. Table 1 The results of Examples 1-3 show that changing the microcapsule particle size in the microencapsulated self-healing epoxy resin material alters the amount of repair agent released by the microcapsules onto the crack surface at the same concentration, thus changing the self-healing performance. When the microcapsule particle size is approximately 70 μm, the self-healing efficiency is approximately 84%; when the microcapsule particle size increases to approximately 100 μm, the self-healing efficiency increases to approximately 92%; when the microcapsule particle size decreases to approximately 50 μm, the self-healing efficiency decreases to approximately 65%. However, overall, since both the repair agent and the matrix material belong to the epoxy class, this homogeneity still endows the self-healing material with a high self-healing ability.

[0052] The results of Examples 1 and 4-6 show that the mass concentration of microcapsules in microencapsulated self-healing epoxy resin materials affects their self-healing performance. As the mass concentration of microcapsules increases, the amount of repair agent released by the microcapsules into the crack surface increases, and the self-healing efficiency also increases accordingly. However, beyond a certain range, the repair efficiency decreases to some extent. When the microcapsule concentration is 5.0 wt%, the self-healing efficiency is approximately 57%; when the microcapsule concentration is 15.0 wt%, the self-healing efficiency increases to 95%; and when the microcapsule concentration is 20.0 wt%, the self-healing efficiency decreases to 93%. At a microcapsule concentration of 20.0 wt%, although the repair agent released by the microcapsules can completely fill the microcracks in the resin matrix, the microcapsules, acting as liquid defects, further reduce the mechanical properties of the self-healing material, such as tensile properties. Furthermore, the toughening effect of the microcapsules actually reduces the apparent self-healing performance of the self-healing material. This indicates that the amount of microcapsules added to microencapsulated self-healing epoxy resin materials should not be too high; 5.0-15.0 wt% is more suitable.

[0053] The results of Example 1 and Comparative Example 7 show that when the microcapsule concentration is too low, such as 2.5 wt%, the total amount of repair agent released from the microcapsules into the microcracks in the epoxy resin matrix also decreases, leading to a significant reduction in the self-healing efficiency of the material. This indicates that the amount of microcapsules added in microcapsule-type self-healing epoxy resin materials cannot be too low.

[0054] The results of Examples 1 and Comparative Examples 2-3 show that the molecular weight of the amine-based repair agent PEI needs to meet a specific range; it cannot be too low or too high. The molecular weight of PEI in Comparative Example 2 is too low, resulting in insufficient long-term thermal stability at service temperatures. This leads to rapid loss of the PEI even after microcapsule formation and addition to the resin matrix, ultimately reducing its self-healing performance. The molecular weight of PEI in Comparative Example 3 is too high. Although it meets the thermal stability requirements, its viscosity is extremely high. On the one hand, this prevents it from diffusing and mixing with another repair agent, BADGE, on the crack surface after release, reducing its repair performance. On the other hand, it prevents it from generating microdroplets through electrostatic spraying and subsequently forming microcapsules to achieve self-healing. A molecular weight of 1000-2000 for PEI is suitable.

[0055] Test Example 3 The structures of the two microcapsules in Example 1 were observed using scanning electron microscopy (SEM). SEM images of the epoxy resin microcapsules and amine microcapsules in Example 1 are shown below. Figure 6As shown, a and c represent epoxy resin microcapsules, b and d represent amine microcapsules, and c and d represent the shell-core structure of the microcapsules. The results show that the epoxy resin microcapsules containing BADGE are approximately 70 μm in size, and the shell-core structure has a thin and dense capsule wall with a thickness of approximately 2 μm. The amine microcapsules containing PEI are approximately 70 μm in size, and the shell-core structure has a rough outer wall and a thin and dense inner wall with a total capsule wall thickness of approximately 2 μm.

[0056] Test Example 4 The thermal stability of the microencapsulated self-healing epoxy resin materials was determined by placing them at the service temperature (100°C) of the epoxy resin for different durations before they broke, including 1 day, 2 days, 4 days, 8 days, 16 days, and 32 days. Then, the self-healing efficiency was quantitatively characterized according to the self-healing performance testing method in Test Example 2.

[0057] Example 1: The self-healing efficiency of microencapsulated self-healing epoxy resin material changes over time after treatment at 100℃. Figure 7 As shown, the results indicate that in the initial stage of heat treatment (1-2 days), the self-healing efficiency of the microencapsulated self-healing epoxy resin material of Example 1 decreased slightly, from 84% in the untreated state to 80%, a decrease of approximately 0.95%. However, with the extension of heat treatment time, the self-healing efficiency no longer decreased and remained at approximately 72%. This demonstrates that the microencapsulated self-healing epoxy resin material possesses excellent thermal stability and can serve for an extended period at the service temperature of the imidazole-cured epoxy resin.

[0058] The self-healing efficiency of the microencapsulated self-healing epoxy resin material in Comparative Example 6 changes over time after treatment at 100℃ as follows: Figure 8 As shown, the results indicate that the self-healing efficiency is as high as 100% without heat treatment. However, the self-healing efficiency decreases rapidly with the extension of heat treatment (100℃). After treatment at 100℃ for 8 days (192h), the self-healing efficiency drops to about 60%, a decrease of up to 40%.

[0059] As can be seen from the above, the thermal stability of the repair agent is crucial to the thermal stability of the self-healing performance of microencapsulated self-healing epoxy resin materials. The repair agent used in this invention, a microencapsulation combination of the highly thermally stable repair agents BADGE and PEI-1800, endows the self-healing material with superior thermal stability.

[0060] The present invention also tested the thermal stability of epoxy resin materials in other embodiments and comparative examples. The test results of the thermal stability of epoxy resin materials in Examples 1-6 and Comparative Examples 1-3 and 6-7 are shown in Table 2. Table 2 Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A microcapsule-type self-healing epoxy resin material with high thermal stability, characterized in that, It is formed by mixing and curing epoxy resin monomers, imidazole curing agent, epoxy resin microcapsules and amine microcapsules. The epoxy resin microcapsules include a capsule wall and an epoxy resin core liquid, and the epoxy resin core liquid contains bisphenol A diglycidyl ether. The amine microcapsules include a capsule wall and an amine core liquid, and the amine core liquid contains tetraethylenepentamine, polyethyleneimine and isophorone diamine. The molecular weight of the polyethyleneimine is 1000~2000 Da; The total amount of epoxy resin microcapsules and amine microcapsules in the microcapsule-type self-healing epoxy resin material is 5% to 20% by mass.

2. The microencapsulated self-healing epoxy resin material as described in claim 1, characterized in that, The mass ratio of epoxy resin microcapsules to amine microcapsules in the microcapsule-type self-healing epoxy resin material is 1:

1.

3. The microencapsulated self-healing epoxy resin material as described in claim 1, characterized in that, The epoxy resin microcapsules have a particle size of 50~100μm; And / or, the particle size of the amine microcapsules is 50~100μm.

4. The microencapsulated self-healing epoxy resin material as described in claim 1, characterized in that, The total amount of epoxy resin microcapsules and amine microcapsules in the microcapsule-type self-healing epoxy resin material is 10%~20% by mass.

5. The microencapsulated self-healing epoxy resin material as described in claim 1, characterized in that, The epoxy resin monomer is bisphenol A type epoxy resin; And / or, the imidazole curing agent is QS-812.

6. The microencapsulated self-healing epoxy resin material as described in claim 5, characterized in that, The bisphenol A type epoxy resin is GELR-128.

7. The microencapsulated self-healing epoxy resin material as described in claim 1, characterized in that, The capsule walls of the epoxy resin microcapsules and the amine microcapsules are both composed of polyurea. And / or, the mass ratio of the epoxy resin monomer to the imidazole curing agent is 100:13.

5.

8. The microencapsulated self-healing epoxy resin material as described in claim 1, characterized in that, The epoxy resin core liquid also contains a diluent, which is n-butyl glycidyl ether; And / or, the mass ratio of tetraethylenepentamine, polyethyleneimine and isophorone diamine in the amine core fluid is 1~2:6~8:1~2.

9. A method for preparing the microencapsulated self-healing epoxy resin material according to any one of claims 1 to 8, characterized in that, The epoxy resin monomer, imidazole curing agent, epoxy resin microcapsules and amine microcapsules are mixed and cured to obtain the final product.

10. The preparation method according to claim 9, characterized in that, The curing process is as follows: first, cure at 50℃~70℃ for 1h~3h, then cure at 90℃~110℃ for 1h~3h, then cure at 110℃~130℃ for 3h~5h, and finally cure at 140℃~160℃ for 4h~6h.

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