Microcapsule type self-repairing imidazole curing epoxy resin as well as preparation method and application thereof

Abstract

The invention relates to microcapsule type self-repairing imidazole curing epoxy resin as well as a preparation method and application thereof. A microcapsule type self-repairing imidazole curing epoxy resin glue solution is provided by adding a bi-component microcapsule, namely an epoxy resin microcapsule and an amine curing agent microcapsule, into a mixture of a basic component imidazole curing agent and an epoxy resin monomer. The glue solution can be prepared into self-repairing imidazole-cured epoxy resin through a curing procedure, epoxy resin microcapsules and amine curing agent microcapsules are less in loss in the curing procedure of the imidazole-cured epoxy resin, have excellent survival performance, and can be used for effectively self-repairing the imidazole-cured epoxy resin after the imidazole-cured epoxy resin is damaged, so that the service life of the imidazole-cured epoxy resin is prolonged, and the service life of the imidazole-cured epoxy resin is prolonged. The damage is completely and autonomously repaired, the self-repairing efficiency is high, and the excellent self-repairing performance is achieved. Meanwhile, the addition of the bi-component microcapsule can also endow the epoxy resin glue solution with good thermal stability.

Description

Technical Field

[0001] This application relates to the technical field of polymer materials, and particularly to a microcapsule-type self-healing imidazole-cured epoxy resin and its preparation method and application. Background Art

[0002] With the continuous progress of technology, various materials are increasingly widely used in modern industry. In particular, epoxy resin has become an important adhesive and coating in many fields (such as aerospace, automotive manufacturing, and electronic products) due to its excellent mechanical properties and chemical corrosion resistance. However, epoxy resin often faces damage problems in actual use, such as cracks and scratches, resulting in a decline in its performance and further affecting the service life and safety of products. Therefore, developing an epoxy resin material with self-healing function has become an important topic in materials science research.

[0003] In recent years, the research on self-healing materials has gradually emerged, and the self-healing method represented by microcapsule technology has attracted much attention. By encapsulating the repair agent in microcapsules, when the material is damaged, the microcapsules rupture and release the repair agent, thus achieving self-healing. This method can effectively extend the service life of materials and reduce maintenance costs. Summary of the Invention

[0004] Based on this, the purpose of this application includes providing a microcapsule-type self-healing imidazole-cured epoxy resin with excellent self-healing performance.

[0005] The technical solution of this application is as follows:

[0006] In the first aspect of the present invention, a microcapsule-type self-healing imidazole-cured epoxy resin adhesive is provided, and its raw materials include epoxy resin monomer, imidazole curing agent, and two-component microcapsules in a mass ratio of (0.5 - 2):(0.5 - 2):(17.5 - 20);

[0007] The two-component microcapsules are a mixture of epoxy resin microcapsules and amine curing agent microcapsules.

[0008] In one embodiment, in the two-component microcapsules, the mass ratio of epoxy resin microcapsules to amine curing agent microcapsules is (1 - 2):1.

[0009] In one embodiment, the epoxy resin microcapsules include a core liquid and a capsule wall;

[0010] The raw materials for preparing the core liquid of the epoxy resin microcapsules include bisphenol F diglycidyl ether and an active diluent; optionally, the active diluent is one or more of n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, tert-butyl glycidyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether;

[0011] The composition of the capsule wall of the epoxy resin microcapsule includes polyurea; the raw materials for preparing the polyurea include isocyanate compounds and aliphatic amine compounds; optionally, the isocyanate compound is one or more of 4,4-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; the aliphatic amine compound is one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0012] In one embodiment, the amine curing agent microcapsule includes a core liquid and a capsule wall;

[0013] The raw materials for preparing the core liquid of the amine curing agent microcapsule include amine compounds; optionally, the raw materials for preparing the core liquid of the amine curing agent microcapsule include tetraethylenepentamine and polyether polyamine; further optionally, in the amine curing agent microcapsule, the mass ratio of tetraethylenepentamine to polyether polyamine is 1:(3 - 6);

[0014] The composition of the capsule wall of the amine curing agent microcapsule includes polyurea; the raw materials for preparing the polyurea include one or more of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.

[0015] In one embodiment, the particle size of the epoxy resin microcapsule is 50μm - 200μm; and / or

[0016] The particle size of the amine curing agent microcapsule is 50μm - 200μm.

[0017] In one embodiment, the epoxy resin monomer is epoxy resin Epolam 5015; and / or

[0018] The imidazole curing agent is an anionic polymerization type epoxy resin curing agent; optionally, the imidazole curing agent is one or more of 1,3-diazacyclopentadiene, 2-methylimidazole, 2-ethylimidazole, or 1-benzyl-2-methylimidazole.

[0019] In the second aspect of the present invention, a microcapsule type self-healing imidazole-cured epoxy resin is provided, which is made of the microcapsule type self-healing imidazole-cured epoxy resin adhesive liquid as described above.

[0020] In the third aspect of the present invention, a preparation method of the microcapsule type self-healing imidazole-cured epoxy resin as described above is provided, including the following steps: mixing the epoxy resin monomer, imidazole curing agent, epoxy resin microcapsule, and amine curing agent microcapsule, and curing.

[0021] In one embodiment, the curing procedure includes: pre-curing at 50°C - 70°C for 1h - 3h, then post-curing at 90°C - 110°C for 1h - 3h, curing at 110°C - 130°C for 3h - 5h, and curing at 140°C - 160°C for 4 - 6h.

[0022] In the fourth aspect of the present invention, there is provided the microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid as described above, or the application of the microcapsule-type self-healing imidazole-cured epoxy resin as described above in the preparation of aerospace, automotive manufacturing or electronic products.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] In the present application, by adding a two-component microcapsule, namely an epoxy resin microcapsule and an amine curing agent microcapsule, to the mixture of the basic components of an imidazole curing agent and an epoxy resin monomer, a microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid is provided. This adhesive liquid can be made into a self-healing imidazole-cured epoxy resin through a curing procedure. The epoxy resin microcapsule and the amine curing agent microcapsule have less loss during the curing procedure of the imidazole-cured epoxy resin, have excellent survival performance, and can effectively self-heal the imidazole-cured epoxy resin after damage, enabling the damage to be completely self-repaired autonomously, with a high self-healing efficiency and excellent self-healing performance.

[0025] Meanwhile, the addition of the two-component microcapsule can also endow the epoxy resin adhesive liquid with good thermal stability.

[0026] In addition, for the preparation method of the microcapsule-type self-healing imidazole-cured epoxy resin provided in the present application, in addition to using epoxy / imidazole containing an epoxy resin microcapsule and an amine curing agent microcapsule, the curing procedure of the epoxy / imidazole is also optimized. The optimized procedure is as follows: First, pre-cure the epoxy / imidazole mixture containing microcapsules at 60°C for 2h to increase the viscosity of the mixture, thereby increasing the resistance during the movement of the microcapsules, avoiding the floating or sinking of the microcapsules caused by the density difference between the microcapsules and the epoxy / imidazole, and promoting the uniform distribution of the microcapsules in the epoxy / imidazole matrix, so as to achieve a higher self-healing efficiency; then continue to cure at 100°C for 2h, 120°C for 4h, and 150°C for 5h in sequence to achieve the complete curing of the epoxy / imidazole matrix. Through the above optimization, the uniform distribution of the microcapsules after the curing of the epoxy / imidazole matrix is promoted, which is beneficial to the improvement of the self-healing performance. Description of the Drawings

[0027] To more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 This is the scanning electron microscope (SEM) image of the epoxy resin microcapsules and amine curing agent microcapsules prepared in Example 1 of the present application. Among them: Figure (a) is the epoxy microcapsules; Figure (b) is the broken epoxy microcapsules; Figure (c) is the enlarged view of the wall of the epoxy microcapsules; Figure (d) is the amine microcapsules; Figure (e) is the broken amine microcapsules; Figure (f) is the enlarged view of the wall of the amine microcapsules.

[0029] Figure 2 This is the distribution diagram of microcapsules in the matrix after the epoxy / imidazole mixture containing microcapsules of the present application is cured according to the traditional curing procedure and the optimized curing procedure. Among them: Figures (a-c) are cured according to the traditional curing procedure; Figures (d-f) are cured according to the optimized curing procedure.

[0030] Figure 3 This is the optical microscope image of the epoxy resin microcapsules and amine curing agent microcapsules in the cured resin of the self-healing imidazole-cured epoxy resin containing 10.0 wt% of 100 μm microcapsules (the ratio of epoxy resin microcapsules to amine curing agent microcapsules is 1:1) in Example 1 of the present application. Among them: Figures (a-c) are the epoxy microcapsules; Figures (d-f) are the amine microcapsules.

[0031] Figure 4 This is the repair performance of the self-healing imidazole-cured epoxy containing 10.0 wt% microcapsules (the mass ratio of epoxy microcapsules to amine microcapsules is 1:1, and the particle size of the microcapsules is about 100 μm). Among them: Figure (a) is the force-displacement curve of the self-healing imidazole-cured epoxy resin using a tapered double cantilever beam (TDCB) specimen during the first fracture and the second fracture after repair. The repair condition is 48 h at room temperature (25 °C); Figure (b) is the trend diagram of the self-healing performance of the self-healing imidazole-cured epoxy resin with the change of the ratio of the two microcapsules. Specific Embodiments

[0032] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will provide a detailed description of the specific embodiments of the present application. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0034] Unless otherwise specified or there is a contradiction, the terms or phrases used herein have the following meanings:

[0035] As used herein, "one or more" refers to any one, any two, or any two or more of the listed items.

[0036] As used herein, the optional scope of "and / or", "or / and", "and / or" includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. (It should be noted that when at least two conjunctions selected from "and / or", "or / and", "and / or" are used to connect at least three items, it should be understood that in this application, this technical solution undoubtedly includes the technical solution connected by "logical AND", and also undoubtedly includes the technical solution connected by "logical OR". For example, "A and / or B" includes three parallel solutions: A, B, and A + B. Another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, D (that is, the technical solution connected by "logical OR"), and also includes any and all combinations of A, B, C, D, that is, it includes the combination of any two or any three of A, B, C, D, and also includes the combination of the four items A, B, C, D (that is, the technical solution connected by "logical AND").)

[0037] As used herein, "further", "even further", "especially", etc. are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0038] In this text, terms such as "first aspect", "second aspect", "third aspect", "fourth aspect", etc. are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. Additionally, terms such as "first", "second", "third", "fourth", etc. are for non-exhaustive listing and description purposes and should be understood not to constitute a closed limitation on quantity. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. In the description of this application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically defined.

[0039] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0040] This text specifically discloses only some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. Additionally, each individually disclosed point or single numerical value itself can be used as a lower or upper limit and combined with any other point or single numerical value or with other lower or upper limits to form a range not explicitly recited. The use of numerical ranges expressed by endpoints includes all numbers within that range and any range within that range. For example, the range from 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0041] In this application, for percentage contents involved, unless otherwise specified, for solid-liquid mixtures and solid-solid mixtures, they refer to mass percentages, and for liquid-liquid mixtures, they refer to volume percentages.

[0042] In this application, for percentage concentrations involved, unless otherwise specified, they all refer to the final concentration. The final concentration refers to the proportion of the added component in the system after adding this component.

[0043] The temperature parameters in this application, unless otherwise specified, allow both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within ranges such as ±5°C, ±2°C, ±1°C, ±0.5°C, ±0.4°C, ±0.3°C, ±0.2°C, ±0.1°C are allowed. Normal temperature or room temperature in this application refers to no temperature control operation, generally referring to 4°C to 35°C, preferably 20 ± 5°C.

[0044] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0045] In the first aspect of the present invention, there is provided a microcapsule-type self-healing imidazole-cured epoxy resin adhesive, and its raw materials include epoxy resin monomers, imidazole curing agents, and two-component microcapsules with a mass ratio of (0.5 - 2) : (0.5 - 2) : (17.5 - 20).

[0046] The two-component microcapsules are a mixture of epoxy resin microcapsules and amine curing agent microcapsules.

[0047] In some examples, in the two-component microcapsules, the mass ratio of epoxy resin microcapsules to amine curing agent microcapsules is (1 - 2) : 1. Further, in the two-component microcapsules, the mass ratio of epoxy resin microcapsules to amine curing agent microcapsules is (1 - 1.5) : 1. It can be understood that in the two-component microcapsules, the mass ratio of epoxy resin microcapsules to amine curing agent microcapsules includes but is not limited to 1 : 1, 1.2 : 1, 1.5 : 1.

[0048] In some examples, the epoxy resin microcapsules include a core liquid and a capsule wall.

[0049] In some examples, the raw materials for preparing the core liquid of the epoxy resin microcapsules include bisphenol F diglycidyl ether and an active diluent; the active diluent is one or more of n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, tert-butyl glycidyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether.

[0050] The composition of the capsule wall of the epoxy resin microcapsules includes polyurea; the raw materials for preparing the polyurea include isocyanate compounds and aliphatic amine compounds; optionally, the isocyanate compounds are one or more of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; the aliphatic amine compounds are one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0051] In some of these examples, the amine curing agent microcapsules include a core liquid and a capsule wall;

[0052] The raw materials for preparing the core liquid of the amine curing agent microcapsules include amine compounds; optionally, the raw materials for preparing the core liquid of the amine curing agent microcapsules include tetraethylenepentamine and polyether polyamine; the composition of the capsule wall of the amine curing agent microcapsules includes polyurea; the raw materials for preparing the polyurea include one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0053] In some of these examples, in the amine curing agent microcapsules, the mass ratio of tetraethylenepentamine to polyether polyamine is 1:(3 - 6). It can be understood that in the amine curing agent microcapsules, the mass ratio of tetraethylenepentamine to polyether polyamine includes but is not limited to 1:3, 1:4, 1:5, 1:6.

[0054] In the two-component repair agent of the present application, that is, the two-component microcapsules, the epoxy resin selects bisphenol F diglycidyl ether (BFDGE) with better thermal stability, and the amine curing agent selects tetraethylenepentamine (TEPA) and polyether polyamine (JEFFAMINE T403) with better thermal stability, which can reduce the loss of the core liquid in the two microcapsules during the curing process, so that during the curing process, the imidazole-cured epoxy resin substrate has better curing performance. After the curing is completed, the microcapsules still retain a considerable amount of core liquid, thereby ensuring that the imidazole-cured epoxy resin realizes the self-healing function.

[0055] At the same time, the capsule walls of the epoxy resin microcapsules and the amine curing agent microcapsules are both composed of polyurea, which has a certain strength and has a good supporting effect on the microcapsules. Moreover, after the curing process is completed, the capsule wall and the resin cured around the microcapsules have an inhibitory effect on the volatilization of the core liquid.

[0056] In some of these examples, the particle size of the epoxy resin microcapsules is 50μm - 200μm. It can be understood that the particle size of the epoxy resin microcapsules includes but is not limited to 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 11μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm.

[0057] In some of these examples, the particle size of the amine curing agent microcapsules is 50μm - 200μm. It can be understood that the particle size of the amine curing agent microcapsules includes but is not limited to 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 11μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm.

[0058] In some of these examples, the preparation method of the epoxy resin microcapsules and amine curing agent microcapsules is the electrostatic spraying-interfacial polymerization composite method. Specifically, in this application, the epoxy resin microcapsules and amine curing agent microcapsules are respectively prepared by the electrostatic spraying-interfacial polymerization composite method. The obtained two-component microcapsules are powders with particle sizes all in the range of 50 μm - 200 μm, which can be conveniently mixed and constructed with existing commercial imidazole-cured epoxy resins; and the thermal stability of this two-component microcapsule - epoxy resin microcapsule and amine curing agent microcapsule is good, and it can be compatible with the curing process of existing commercial imidazole-cured epoxy resins, and basically does not affect other properties of existing imidazole-cured epoxy resins.

[0059] In some of these examples, the epoxy resin monomer is epoxy resin Epolam 5015.

[0060] In some of these examples, the imidazole curing agent is an anionic polymerization type epoxy resin curing agent; optionally, the imidazole curing agent is one or more of 1,3-diazacyclopentadiene, 2-methylimidazole, 2-ethylimidazole or 1-benzyl-2-methylimidazole.

[0061] In the second aspect of the present invention, there is provided a microcapsule-type self-healing imidazole-cured epoxy resin, which is made from the microcapsule-type self-healing imidazole-cured epoxy resin liquid as described above.

[0062] Imidazole, as a common curing agent, is widely used in the curing system of epoxy resins due to its excellent curing performance and environmental friendliness. After a large number of studies by the technical personnel of this application, a novel self-healing epoxy resin is innovatively proposed, aiming to introduce microcapsules containing epoxy monomers and microcapsules containing amine curing agents into the epoxy resin to achieve the self-healing function of imidazole-cured epoxy resins. This innovation not only improves the performance of epoxy resins, but also provides new ideas for the research of self-healing materials. Through this method, the damaged epoxy resin can self-repair under certain conditions and restore its original mechanical properties and functions, thus showing higher reliability and durability in a variety of application scenarios.

[0063] In the third aspect of the present invention, there is provided a preparation method of the microcapsule-type self-healing imidazole-cured epoxy resin as described above, including the following steps: mixing the epoxy resin monomer, imidazole curing agent, epoxy resin microcapsules and amine curing agent microcapsules, and curing.

[0064] In some of these examples, the curing procedure includes: pre-curing at 50°C - 70°C for 1h - 3h, then post-curing at 90°C - 110°C for 1h - 3h, curing at 110°C - 130°C for 3h - 5h, and curing at 140°C - 160°C for 4h - 6h. Further, the curing procedure includes: pre-curing at 60°C for 2h, then curing at 100°C for 2h, curing at 120°C for 4h, and curing at 140°C for 5h. To avoid the floating or sinking of the microcapsules containing the repair agent due to the density difference from epoxy / imidazole, the present application innovatively adds a pre-curing process (pre-curing at 60°C for 2h) on the basis of the original curing procedure of epoxy / imidazole (curing at 100°C for 2h, curing at 120°C for 4h, and curing at 150°C for 5h) in sequence, so as to increase the viscosity of the epoxy / imidazole adhesive, increase the resistance during the floating / sinking of the microcapsules, and promote the uniform distribution of the microcapsules in the epoxy / imidazole matrix, in order to achieve a higher self-healing efficiency.

[0065] In the fourth aspect of the present invention, there is provided the microcapsule-type self-healing imidazole-cured epoxy resin adhesive as described above, or the application of the microcapsule-type self-healing imidazole-cured epoxy resin as described above in the preparation of aerospace, automotive manufacturing or electronic products. Without limitation, the application includes making the microcapsule-type self-healing imidazole-cured epoxy resin adhesive as described above, or the microcapsule-type self-healing imidazole-cured epoxy resin as described above into an adhesive or a coating.

[0066] The following is further described with specific examples. For the raw materials involved in the following specific examples, unless otherwise specified, they can all be obtained commercially; for the instruments used, unless otherwise specified, they can all be obtained commercially; for the processes involved, unless otherwise specified, they are all conventional selections of those skilled in the art.

[0067] Some of the raw materials used in the examples are as follows:

[0068] Epolam 5015 (trade name) was purchased from Axson Technologies of France;

[0069] Hardener 5014 (trade name) was purchased from Axson Technologies of France;

[0070] Arlacel P135 (trade name) was purchased from Croda International Plc of the UK.

[0071] HMDI, chemically named 4,4'-dicyclohexylmethane diisocyanate, was purchased from Wanhua Chemical Group Co., Ltd. of Yantai.

[0072] The following are specific examples.

[0073] Example 1

[0074] This embodiment is for the preparation of the optimized cured self-healing imidazole-cured epoxy resin provided by this application, which is specifically as follows:

[0075] (1) 90 parts of bisphenol F diglycidyl ether (BFDGE) and 10 parts of the active diluent n-butyl glycidyl ether (BGE) were mixed evenly to form F10B epoxy resin. 95 parts of this epoxy solution and 5 parts of 4,4'-dicyclohexylmethane diisocyanate (HMDI) were mixed evenly to form the core liquid to be encapsulated. After loading this core liquid into a syringe, it was extruded at a rate of 8.0 mL / h and atomized under a static voltage of 22 kV to form core liquid micro-droplets. A reaction solution containing 100.0 mL of deionized water, 1.0 g of sodium dodecyl sulfonate, and 12.0 g of diethylenetriamine was used to receive the above core liquid micro-droplets to form primary micro-capsules containing epoxy resin. After the preparation of the primary micro-capsules was completed, the mixture of the above primary micro-capsules and the reaction solution was reacted at 90 °C for 10 h to form the final micro-capsules containing epoxy resin. Finally, after washing with water, filtering, and drying at room temperature, finished micro-capsules with a particle size of about 100 μm, a polyurea capsule wall, and an epoxy resin monomer core material were obtained.

[0076] (2) 15 parts of tetraethylenepentamine (TEPA) and 85 parts of polyether polyamine (JEFFAMINE T403) were mixed evenly to form a 15TEPA85T403 mixed amine curing agent; a n-hexadecane solution and a decalin solution containing 2.0 wt% surfactant Arlacel P135 and 0.1 wt% catalyst diethylenetriamine were prepared. After loading 15TEPA85T403 into a syringe, it was extruded at a rate of 10.0 mL / h and atomized under a static voltage of 20 kV to form core liquid micro-droplets. A reaction solution containing 75 mL of n-hexadecane, 75 mL of decalin, 2.0 wt% surfactant Arlacel P135, 0.1 wt% catalyst diethylenetriamine, and 18 g of the shell-forming monomer HMDI was used to receive the above core liquid micro-droplets to form primary micro-capsules containing amine curing agent. After the preparation of the primary micro-capsules was completed, the mixture of the above primary micro-capsules and the reaction solution was reacted at 80 °C for 3 h to form the final micro-capsules containing amine curing agent. Finally, after washing with cyclohexane, filtering, and drying at room temperature, finished micro-capsules with a particle size of about 100 μm, a polyurea capsule wall, and an amine curing agent core material were obtained.

[0077] (3)Prepare the tapered double cantilever beam (TDCB) sample frame using epoxy resin Epolam 5015 and its curing agent Hardener 5014 at a mass ratio of 100:34. The curing procedure is to cure at room temperature (25°C) for 24 h. Take 1.0 g of epoxy resin microcapsules and 1.0 g of amine curing agent microcapsules, premix them evenly and then add them to a mixture of 18.0 g of epoxy resin monomer and imidazole curing agent (1-benzyl-2-methylimidazole) (the mass ratio of the two is 100:13.5), and mix them evenly. Add the epoxy resin glue containing microcapsules to the test groove of the TDCB sample frame and cure it with a stepwise heating program of 60°C for 2 h, 100°C for 2 h, 120°C for 4 h, and 140°C for 5 h to form a microcapsule-type self-healing imidazole-cured epoxy resin.

[0078] Example 2

[0079] This example is basically the same as Example 1, and the main difference is that the mass ratio of epoxy resin microcapsules to amine curing agent microcapsules is 1.2:1.

[0080] Example 3

[0081] This example is basically the same as Example 1, and the main difference is that the mass ratio of epoxy resin microcapsules to amine curing agent microcapsules is 1.5:1.

[0082] Comparative Example 1

[0083] This comparative example is for the preparation of pure imidazole-cured epoxy resin, which is specifically as follows:

[0084] Prepare the TDCB sample frame using epoxy resin Epolam 5015 and its curing agent Hardener 5014 at a mass ratio of 100:34. The curing procedure is to cure at room temperature (25°C) for 24 h. Add the premixed mixture of epoxy resin monomer and imidazole curing agent (1-benzyl-2-methylimidazole) (the mass ratio of the two is 100:13.5) to the test groove of the TDCB sample frame and cure it with a stepwise heating program of 60°C for 2 h, 100°C for 2 h, 120°C for 4 h, and 140°C for 5 h to form a test sample of pure imidazole-cured epoxy resin.

[0085] Comparative Example 2

[0086] This comparative example is for the preparation of self-healing imidazole-cured epoxy resin according to the traditional curing procedure, which is basically the same as Example 1, and the main difference is that the curing of epoxy / imidazole uses a stepwise heating program of 100°C for 2 h, 120°C for 4 h, and 140°C for 5 h.

[0087] The products of each example and each comparative example are tested as follows:

[0088] (1)Morphology analysis: The scanning electron microscope (SEM) was used to characterize the microscopic morphology. Figure 1 (a) shows the SEM image of the prepared epoxy microcapsules, and the size of the microcapsules is about 100 μm; Figure 1 (b) shows the shell-core structure of the epoxy microcapsules; Figure 1 (c) shows the wall structure of the epoxy microcapsules. The wall is thin and dense, with a thickness of about 2 μm; Figure 1 (d) shows the SEM image of the prepared amine microcapsules, and the size of the microcapsules is about 100 μm; Figure 1 (e) shows the shell-core structure of the amine microcapsules; Figure 1 (f) shows the wall structure of the amine microcapsules. The outer wall of the wall is rough, the inner wall is thin and dense, and the total thickness is about 2 μm.

[0089] Figure 2 (a-c) shows the distribution map of the microcapsules in the matrix after the epoxy / imidazole mixture containing microcapsules is cured according to the traditional curing procedure. When the mixture is directly heated to 100 °C during curing according to the traditional curing procedure, the viscosity of the mixture decreases sharply, resulting in the floating / sinking of the microcapsules due to the density difference between the microcapsules and the epoxy / imidazole adhesive solution. Among them, the epoxy microcapsules sink and concentrate at the bottom of the sample, while the amine microcapsules float and concentrate at the top of the sample. Eventually, the uneven distribution of the two types of microcapsules after the epoxy / imidazole curing is caused, thus affecting the self-healing performance. Figure 2 (d-f) shows the distribution map of the microcapsules in the matrix after the epoxy / imidazole mixture containing microcapsules is cured according to the optimized curing procedure. The mixture is first pre-cured at 60 °C for 2 h to increase the viscosity of the mixture, thereby increasing the resistance during the movement of the microcapsules, avoiding the floating or sinking of the microcapsules caused by the density difference between the microcapsules and the epoxy / imidazole, and promoting the uniform distribution of the microcapsules in the epoxy / imidazole matrix in order to achieve a higher self-healing efficiency.

[0090] (2) Thermal stability test: The optical microscope was used to characterize the microscopic morphology. Figure 3 (a-c) and (d-f) respectively show the thermal stability of the epoxy microcapsules and the amine microcapsules under this epoxy / imidazole curing procedure. The epoxy microcapsules show excellent thermal stability under the epoxy / imidazole curing procedure, and the epoxy repair agent in the microcapsules does not lose due to volatilization. The amine microcapsules show relatively high thermal stability under the epoxy / imidazole curing procedure. The black area at the top of the microcapsules is the void left after the core liquid part in the microcapsules volatilizes. Although a certain degree of volatilization of the amine repair agent in the amine microcapsules occurs, most of the amine repair agent still remains in the microcapsules.

[0091] (3)Mechanical property test: In the test groove of the TDCB specimen of the microcapsule-type self-healing imidazole-cured epoxy resin and the pure imidazole-cured epoxy resin, a crack with a length of 8-10 mm was prefabricated first. Then, after fixing the sample with a mechanical universal testing machine, the specimen was pulled apart along the prefabricated crack in the test groove of the TDCB specimen at a loading rate of 1 mm / min (primary fracture). After placing the specimen in a constant temperature and humidity chamber at 25 °C for 48 h of curing, the specimen was pulled apart again at the same loading rate using a mechanical universal testing machine (secondary fracture after repair). Record the force-displacement curve during the test process, and take the highest point of the curve to calculate the self-healing efficiency based on fracture toughness repair. Figure 4 Figure (a) shows the force-displacement curves of the self-healing imidazole-cured epoxy resin using the TDCB specimen during primary fracture and secondary fracture after repair. As can be seen from the figure, the microcapsule-type self-healing imidazole-cured epoxy resin has excellent self-healing performance, and its self-healing efficiency (the force peak value of the force-displacement curve during secondary fracture after repair divided by the force peak value of the force-displacement curve during primary fracture) is 104.75%. Figure 4 Figure (b) shows the variation trend of the self-healing efficiency of the microcapsule-type self-healing imidazole-cured epoxy resin with the mass ratio of epoxy microcapsules to amine microcapsules. As can be seen from the figure, when the mass ratio of the two types of microcapsules is 1:1, the average self-healing efficiency is as high as 102%. When the mass ratios of the two types of microcapsules are 1.2:1 and 1.5:1, the average self-healing efficiencies are 92% and 96% respectively. Thus, when the ratio of the two types of microcapsules changes, the self-healing imidazole-cured epoxy resin exhibits excellent self-healing performance.

[0092] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0093] The above-described embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can be made, and these all belong to the protection scope of the present application. In addition, it should be understood that after reading the above teachings of the present application, those skilled in the art can make various changes or modifications to the present application, and the equivalent forms obtained also fall within the protection scope of the present application. It should also be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided in the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the specification can be used to explain the content of the claims.

Claims

1. A microcapsule-type self-healing imidazole-cured epoxy resin adhesive solution, characterized in that, Its raw materials include an epoxy resin monomer, an imidazole curing agent, and a two-component microcapsule in a mass ratio of (0.5 - 2):(0.5 - 2):(17.5 - 20). The two-component microcapsule is a mixture of an epoxy resin microcapsule and an amine curing agent microcapsule.

2. The microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid according to claim 1, characterized in that, In the two-component microcapsule, the mass ratio of the epoxy resin microcapsule to the amine curing agent microcapsule is (1 - 2):

1.

3. The microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid according to claim 1, characterized in that, The epoxy resin microcapsule includes a core liquid and a capsule wall. The raw materials for preparing the core liquid of the epoxy resin microcapsule include bisphenol F diglycidyl ether and an active diluent; optionally, the active diluent is one or more of n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, tert-butyl glycidyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether. The composition of the capsule wall of the epoxy resin microcapsule includes polyurea; the raw materials for preparing the polyurea include isocyanate compounds and aliphatic amine compounds; optionally, the isocyanate compounds are one or more of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; the aliphatic amine compounds are one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

4. The microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid according to claim 1, characterized in that The amine curing agent microcapsule includes a core liquid and a capsule wall. The raw materials for preparing the core liquid of the amine curing agent microcapsule include amine compounds; optionally, the raw materials for preparing the core liquid of the amine curing agent microcapsule include tetraethylenepentamine and polyether polyamine; further optionally, the mass ratio of tetraethylenepentamine to polyether polyamine is 1:(3 - 6). The composition of the capsule wall of the amine curing agent microcapsule includes polyurea; the raw materials for preparing the polyurea include one or more of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.

5. The microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid according to any one of claims 1-4, characterized in that, The particle size of the epoxy resin microcapsule is 50μm - 200μm; and / or The particle size of the amine curing agent microcapsule is 50μm - 200μm.

6. The microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid according to any one of claims 1 to 4, characterized in that, The epoxy resin monomer is epoxy resin Epolam 5015; and / or The imidazole curing agent is an anionic polymerization type epoxy resin curing agent; optionally, the imidazole curing agent is one or more of 1,3-diazacyclopentadiene, 2-methylimidazole, 2-ethylimidazole, or 1-benzyl-2-methylimidazole.

7. A microcapsule-type self-healing imidazole-cured epoxy resin, characterized in that, It is made from the microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid described in any one of claims 1 - 6.

8. A preparation method of the microcapsule-type self-healing imidazole-cured epoxy resin as described in claim 7, characterized in that, It includes the following steps: mixing the epoxy resin monomer, imidazole curing agent, epoxy resin microcapsule, and amine curing agent microcapsule, and curing.

9. The preparation method of the microcapsule-type self-healing imidazole-cured epoxy resin according to claim 8, wherein, The curing procedure includes: pre-curing at 50℃ - 70℃ for 1h - 3h first, then post-curing at 90℃ - 110℃ for 1h - 3h, curing at 110℃ - 130℃ for 3h - 5h, and curing at 140℃ - 160℃ for 4h - 6h.

10. The application of the microcapsule-type self-healing imidazole-cured epoxy resin adhesive liquid described in any one of claims 1 - 6, or the microcapsule-type self-healing imidazole-cured epoxy resin described in claim 7 in the preparation of aerospace, automotive manufacturing, or electronic products.

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