Repairable thermoset material containing schiff base type dynamic covalent bond and preparation method and application thereof

Abstract

The application discloses a repairable thermosetting material containing a Schiff base type dynamic covalent bond and a preparation method thereof. The application introduces the Schiff base type dynamic covalent bond into the crosslinking network of a resin polymer, gives the material remoldability and reworkability, and has the advantages of both thermosetting materials and thermoplastic materials. Meanwhile, the application introduces 4,4'-diamino diphenyl ether or 4,4'-diamino diphenylamine containing a benzene ring, and the large conjugate structure of the imine bond adjacent to the benzene ring strengthens the weak imine bond, solves the problems of poor mechanical properties and heat resistance of the imine material, guarantees the stability of the dynamic performance of the material, and the method for preparing the repairable thermosetting material containing the Schiff base type dynamic covalent bond is carried out under relatively mild conditions.

Description

[0001] The technical field

[0002] The present application relates to the technical field of thermosetting materials, in particular to a repairable thermosetting material containing a Schiff base type dynamic covalent bond and a preparation method and application thereof. BACKGROUND

[0003] In high molecular polymer materials, thermosetting resin becomes the first choice of resin for structural composite material application due to its excellent mechanical properties, heat resistance, dimensional stability, etc., such as the manufacture of aerospace composite material parts which have high requirements for rigidity and durability. The traditional thermosetting resin is a monomer molecule which forms a three-dimensional network structure through chemical reaction under the action of heating, pressurization or curing agent. This is an irreversible crosslinking structure which cannot be repeatedly processed and formed during polymerization, and is difficult to recycle after being discarded, resulting in environmental pollution and resource waste, which has become a problem that cannot be ignored. Therefore, more and more people begin to study and design reusable thermosetting materials. However, the mechanical properties and heat resistance of the current reusable thermosetting materials need to be improved. One of the repairable thermosetting materials is a Schiff base type dynamic covalent bond, but the instability of the imine bond causes poor mechanical properties of the material, and the heat resistance also needs to be improved.

[0004] Therefore, it is urgent for the person skilled in the art to develop a reusable thermosetting material with good mechanical properties and heat resistance. SUMMARY

[0005] In order to solve the problems in the prior art, the present application introduces a Schiff base type dynamic covalent bond into the crosslinking network to obtain a material with a three-dimensional network structure; the amino group and the aldehyde group undergo Schiff base reaction to form an imine bond, and the imine bond undergoes reversible rearrangement reaction at a certain temperature, such as Figure 1As shown, the imine bond (a, b) is broken at the same time, and a new imine bond (a', b) is formed, giving the material remoldability and reworkability. Specifically, the material can exhibit classic thermosetting under certain conditions, but when the glass is heated to a ductile state, the dynamic covalent bond is activated, and the bond exchange reaction can occur, and the network topology can be repeatedly rearranged. The reversibility of the glass enables the fully cured material to be welded, shaped, remolded and recycled. At the same time, the present application introduces a benzene ring-containing 4,4'-diamino diphenyl ether or 4,4'-diamino diphenylamine, which is reacted with p-xylylene glycol together with diamines and triamines to cross-link into a body-shaped structure. When the cross-linking reaction proceeds to a certain extent, the system becomes a gel state that cannot flow. The large conjugated structure of the imine bond adjacent to the benzene ring enhances the weak imine bond, retains the toughness of the material, solves the problem of poor mechanical properties of imine materials, and ensures the stability of the dynamic performance of the material. The method for preparing the repairable thermosetting material containing the Schiff base type dynamic covalent bond can be carried out under relatively mild conditions.

[0006] One of the purposes of the present application is to provide a repairable thermosetting material containing a Schiff base type dynamic covalent bond.

[0007] A repairable thermosetting material containing a Schiff base type dynamic covalent bond, the repairable thermosetting material is prepared from raw materials comprising the following components:

[0008]

[0009] The diamine is any one of difunctional polyether amine, hexanediamine, N,N-bis(3-aminopropyl)methylamine;

[0010] The triamine is a trifunctional polyether amine or diethylenetriamine.

[0011] Since the number of covalent bonds in the cross-linked network remains unchanged, the original performance of the material does not change substantially, and the material containing the Schiff base type dynamic covalent bond prepared by the present application still has good elongation at break and toughness, which can effectively improve the service life of the material, and has certain strength. Although their total cross-linking density remains unchanged, the bond exchange rate increases with increasing temperature, because all chemical reactions run faster at higher temperatures. This results in a gradual decrease in viscosity with temperature, which is different from the relatively sudden decrease in viscosity associated with the melt transition of thermoplastic materials.

[0012] In a preferred embodiment of the present application, the components are as follows in parts by weight:

[0013]

[0014]

[0015] In a more preferred embodiment of the present application, the components are in parts by weight,

[0016]

[0017] In a preferred embodiment of the present application, the difunctional polyether amine is any one of D230, D400, D2000, and D4000, wherein the number average molecular weight of D230 is 230, the number average molecular weight of D400 is 400, the number average molecular weight of D2000 is 2000, and the number average molecular weight of D4000 is 4000. The trifunctional polyether amine is T403 or T5000, wherein the number average molecular weight of T403 is 440, and the number average molecular weight of T5000 is 5000. The skilled person can select the type and amount of the difunctional polyether amine and the trifunctional polyether amine as appropriate. Taking the difunctional polyether amine as D230, the trifunctional polyether amine as T403, and the 4,4'-diamino diphenyl ether (ODA for short) as an example, the chemical reaction equation of the three is as follows:

[0018]

[0019] As can be seen from the chemical equation, the introduction of ODA forms a large conjugate structure adjacent to the imine bond and the benzene ring in the original system, the stability of the compound is enhanced, and therefore the mechanical properties of the final material are enhanced.

[0020] In a preferred embodiment of the present application, the ratio of the total moles of the diamine and the 4,4'-diamino diphenyl ether to the moles of the triamine is 1:0.3-6, or the ratio of the total moles of the diamine and the 4,4'-diamino diphenyl ether to the moles of the triamine is 1:0.3-6. In another preferred embodiment of the present application, the molar ratio of the diamine to the 4,4'-diamino diphenyl ether is 1:0.5-2, or the molar ratio of the diamine to the 4,4'-diamino diphenyl ether is 1:0.5-2. The skilled person can select the ratio of the total moles of the diamine and the 4,4'-diamino diphenyl ether to the moles of the triamine, the molar ratio of the diamine to the 4,4'-diamino diphenyl ether, and the molar ratio of the diamine to the 4,4'-diamino diphenyl ether as appropriate.

[0021] In a preferred embodiment of the present application, the solvent is N,N-dimethylformamide or ethanol. The skilled person can select the appropriate solvent and amount as appropriate.

[0022] The second object of the present application is to provide a method for preparing the repairable thermoset material containing a Schiff base type dynamic covalent bond according to the first object of the present application.

[0023] The repairable thermoset material is prepared by the following steps:

[0024] 4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenylamine, p-xylene dicarboxaldehyde, diamine, triamine are dissolved in a solvent, heated, and a repairable thermoset material containing a Schiff base type dynamic covalent bond is obtained after reaction.

[0025] The application can specifically adopt the following technical solutions:

[0026] Taking 4,4'-diaminodiphenyl ether as an example, the repairable thermoset material is prepared by the following steps:

[0027] The p-xylene dicarboxaldehyde is added with a solvent and shaken, and after the solid is completely dissolved or a small amount of solid remains, the diamine is added dropwise into the p-xylene dicarboxaldehyde dissolved in the solvent and shaken uniformly. Then, the 4,4'-diaminodiphenyl ether is also added and shaken uniformly. The solid dissolution is observed, and if there is undissolved solid, an appropriate amount of solvent is added and shaken until the solid is completely dissolved. The triamine is also added dropwise and stirred to mix uniformly. The uniformly mixed solution is added dropwise into a silica gel mold, vacuum degassed, and then transferred to a flat plate heater until the sample becomes a gel. The gel sample is transferred to an oven for further reaction, and a polyimine resin containing a Schiff base type dynamic covalent bond is obtained.

[0028] It should be noted that the imine formed by the primary amine and aldehyde or ketone in the preparation method of the application belongs to condensation reaction, and water molecules are generated. In the reaction process, the generated water in the system is continuously removed, which can promote the reaction equilibrium to move in the direction of generating imine. Therefore, the Schiff base reaction between the amino group and the aldehyde group to form the imine bond can be slowly carried out at room temperature without external stimulation, which to some extent makes the reaction conditions more mild, so that the dynamic exchange can be stimulated to be realized without going through harsh conditions as in general self-healing materials, and the operation is simple and easy to repeat.

[0029] In a preferred embodiment of the application, the reaction temperature is 80-100 DEG C, and the reaction time is 4-10 h. The skilled person can select appropriate reaction temperature and reaction time as appropriate.

[0030] The third application purpose of the application is to provide an application of the repairable thermoset material containing a Schiff base type dynamic covalent bond in sports equipment, aviation, automobiles, wind energy and gas storage pressure vessels.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] 1.The present application can adjust the structure of the crosslinked network by introducing 4,4'-diamino diphenyl ether or 4,4'-diamino diphenylamine with benzene ring into the imine network to form a large conjugated structure of benzene ring and imine bond, thereby retaining the original toughness of the material on one hand, and the large conjugated structure has a reinforcing effect on the weak imine bond, improving the mechanical properties of the material while retaining the self-repairing advantage of the system, solving the problem of instability of the existing technology containing Schiff base type dynamic covalent bond repairable thermosetting material.

[0033] 2.The present application can prepare a degradable, environmentally friendly repairable thermosetting material containing Schiff base type dynamic covalent bond.

[0034] 3.The preparation process of the repairable thermosetting material containing Schiff base type dynamic covalent bond of the present application does not require the use of catalyst, the experimental conditions are mild, and the repair and reshaping of the material can be completed in a short time without special instruments, which is more convenient in practical application. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The dynamic covalent bond of the repairable thermosetting resin containing Schiff base type dynamic covalent bond obtained by the present application is shown in the figure.

[0036] Figure 2 The infrared spectrum of the repairable thermosetting resin containing Schiff base type dynamic covalent bond obtained by the present application is shown in the figure.

[0037] Figure 3 The repairable thermosetting resin containing Schiff base type dynamic covalent bond obtained by the present application is cut into segments.

[0038] Figure 4 The repairable thermosetting resin containing Schiff base type dynamic covalent bond obtained by the present application is shown in the figure.

[0039] Figure 5 The storage modulus (E') of the present application examples 1-3 and the comparative example 1 is shown in the figure.

[0040] Figure 6 The loss modulus (E'') of the present application examples 1-3 and the comparative example 1 is shown in the figure.

[0041] Figure 7 The loss factor (tan delta) of the present application examples 1-3 and the comparative example 1 is shown in the figure. DETAILED DESCRIPTION

[0042] The application will be described in detail below with reference to specific drawings and examples. It is necessary to point out that the following examples are only used to further illustrate the application and cannot be understood as limiting the protection scope of the application. Some non-essential improvements and adjustments of the application made by those skilled in the art according to the content of the application still fall within the protection scope of the application.

[0043] The raw materials used in the examples are all conventional commercially available raw materials. Terephthaldehyde (chemically pure, TCI); D230 (one of the trade names of difunctional polyether amine, number average molecular weight 230, analytically pure); D400 (one of the trade names of difunctional polyether amine, number average molecular weight 400, analytically pure); 4,4'-diamino diphenyl ether (ODA, molecular weight 200.24); T403 (one of the trade names of trifunctional polyether amine, number average molecular weight 440); N,N-dimethylformamide (DMF, chemically pure, MERYER).

[0044] Example 1

[0045] In a beaker, 100 parts by weight of terephthaldehyde was accurately weighed, 671.64 parts by weight of solvent N,N-dimethylformamide was added, shaken, and after the solid was completely dissolved or a small amount of solid remained, 11.19 parts by weight of D230 was accurately weighed and added dropwise to the beaker, shaken, 5.22 parts by weight of ODA was accurately weighed with weighing paper, added to the beaker, and shaken. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 197 parts by weight of T403, add dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix evenly. Add dropwise to a silica gel mold, vacuum degas for 10 min, then transfer to an 80°C flat plate heater until the sample gel, then transfer to a 100°C oven for further reaction for 4 h, to obtain a repairable thermosetting resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:6:1. Among them, the molar ratio of D230 and ODA is about 2:1.

[0046] Example 2

[0047] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 671.64 parts by weight of solvent N,N-dimethylformamide, shake, and when the solid is completely dissolved or a small amount of solid remains, accurately weigh 8.58 parts by weight of D230 and add it dropwise to the beaker, shake, accurately weigh 7.46 parts by weight of ODA with a weighing paper, add it to the beaker, and shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 197 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix uniformly. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to an 80°C flat plate heater until the sample gel is formed, and then transfer it to a 100°C oven for further reaction for 4 h, to obtain a repairable thermosetting resin containing a Schiff base type dynamic covalent bond. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:6:1. Among them, the molar ratio of D230 and ODA is about 1:1.

[0048] Example 3

[0049] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 671.64 parts by weight of solvent N,N-dimethylformamide, shake, and when the solid is completely dissolved or a small amount of solid remains, accurately weigh 8.58 parts by weight of D230 and add it dropwise to the beaker, shake, accurately weigh 7.46 parts by weight of ODA with a weighing paper, add it to the beaker, and shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 197 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix uniformly. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to an 80°C flat plate heater until the sample gel is formed, and then transfer it to a 100°C oven for further reaction for 4 h, to obtain a repairable thermosetting resin containing a Schiff base type dynamic covalent bond. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:6:1. Among them, the molar ratio of D230 and ODA is about 1:1.

[0050] Example 4

[0051] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, and wait until the solid is completely dissolved or a small amount of solid remains. Accurately weigh 45.75 parts by weight of D230 and add it dropwise to the beaker, shake, and accurately weigh 19.93 parts by weight of ODA on a weighing paper and add it to the beaker, shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 131.34 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix evenly. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to an 80°C flat plate heater until the sample gel is formed, and then transfer it to a 100°C oven for further reaction for 4 h, to obtain a repairable thermosetting resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:4:4. Among them, the molar ratio of D230 and ODA is about 2:1.

[0052] Example 5

[0053] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, and wait until the solid is completely dissolved or a small amount of solid remains. Accurately weigh 45.75 parts by weight of D230 and add it dropwise to the beaker, shake, and accurately weigh 19.93 parts by weight of ODA on a weighing paper and add it to the beaker, shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 131.34 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix evenly. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to an 80°C flat plate heater until the sample gel is formed, and then transfer it to a 100°C oven for further reaction for 4 h, to obtain a repairable thermosetting resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:4:4. Among them, the molar ratio of D230 and ODA is about 2:1.

[0054] Example 6

[0055] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, and wait until the solid is completely dissolved or a small amount of solid remains. Accurately weigh 22.46 parts by weight of D230 and add it dropwise to the beaker, shake well, and accurately weigh 39.78 parts by weight of ODA using a weighing paper, add it to the beaker, and shake well. Observe the dissolution of the solid, if there are undissolved solids, add an appropriate amount of DMF solvent, shake well, until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 131.34 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix well. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to a 80℃ flat plate heater until the sample gel is formed, then transfer it to a 100℃ oven for further reaction for 4h, to obtain a repairable thermoset resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, T403 is 10:4:4. Among them, the molar ratio of D230 and ODA is about 1:2.

[0056] Example 7

[0057] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, and wait until the solid is completely dissolved or a small amount of solid remains. Accurately weigh 22.46 parts by weight of D230 and add it dropwise to the beaker, shake well, and accurately weigh 39.78 parts by weight of ODA using a weighing paper, add it to the beaker, and shake well. Observe the dissolution of the solid, if there are undissolved solids, add an appropriate amount of DMF solvent, shake well, until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 131.34 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix well. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to a 80℃ flat plate heater until the sample gel is formed, then transfer it to a 100℃ oven for further reaction for 4h, to obtain a repairable thermoset resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, T403 is 10:4:4. Among them, the molar ratio of D230 and ODA is about 1:2.

[0058] Example 8

[0059] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 675.18 parts by weight of solvent N,N-dimethylformamide, shake, and wait until the solid is completely dissolved or a small amount of solid remains. Accurately weigh 60.07 parts by weight of D230 and add it dropwise to the beaker, shake, and accurately weigh 52.24 parts by weight of ODA using a weighing paper, add it to the beaker, and shake. Observe the dissolution of the solid, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 65.67 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix evenly. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to an 80°C flat plate heater until the sample gel is formed, then transfer it to a 100°C oven for further reaction for 4 h, to obtain a repairable thermoset resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:7:2. Among them, the molar ratio of D230 and ODA is about 1:1.

[0060] Example 9

[0061] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 675.18 parts by weight of solvent N,N-dimethylformamide, shake, and wait until the solid is completely dissolved or a small amount of solid remains. Accurately weigh 40.07 parts by weight of D230 and add it dropwise to the beaker, shake, and accurately weigh 69.63 parts by weight of ODA using a weighing paper, add it to the beaker, and shake. Observe the dissolution of the solid, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 65.67 parts by weight of T403, add it dropwise to the beaker, use a clean dropper, stir for 1-2 min, and mix evenly. Add it to the silica gel mold, vacuum degassing for 10 min, then transfer it to an 80°C flat plate heater until the sample gel is formed, then transfer it to a 100°C oven for further reaction for 4 h, to obtain a repairable thermoset resin containing Schiff base type dynamic covalent bonds. In this example, the molar ratio of terephthaldehyde, D230+ODA, and T403 is 10:7:2. Among them, the molar ratio of D230 and ODA is about 1:2.

[0062] Example 10

[0063] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, wait until the solid is completely dissolved or a small amount of solid is left, accurately weigh 60 parts by weight of D400, drop into the beaker, shake, accurately weigh 30 parts by weight of 4,4'-diaminodiphenylamine with weighing paper, add to the beaker, shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 31 parts by weight of diethylenetriamine, drop into the beaker, use a clean dropper, stir for 1-2 min, mix evenly. Add to the silica gel mold, vacuum degassing for 10 min, then transfer to a 60℃ flat plate heater until the sample gel, then transfer to a 100℃ oven for 4h to continue the reaction, to obtain a repairable thermosetting resin containing Schiff base type dynamic covalent bonds.

[0064] Example 11

[0065] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, wait until the solid is completely dissolved or a small amount of solid is left, accurately weigh 60 parts by weight of D400, drop into the beaker, shake, accurately weigh 30 parts by weight of 4,4'-diaminodiphenylamine with weighing paper, add to the beaker, shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 31 parts by weight of diethylenetriamine, drop into the beaker, use a clean dropper, stir for 1-2 min, mix evenly. Add to the silica gel mold, vacuum degassing for 10 min, then transfer to a 60℃ flat plate heater until the sample gel, then transfer to a 100℃ oven for 4h to continue the reaction, to obtain a repairable thermosetting resin containing Schiff base type dynamic covalent bonds.

[0066] Comparative Example 1

[0067] In a beaker, accurately weigh 100 parts by weight of terephthaldehyde, add 672.23 parts by weight of solvent N,N-dimethylformamide, shake, wait until the solid is completely dissolved or a small amount of solid is left, accurately weigh 60 parts by weight of D400, drop into the beaker, shake, accurately weigh 30 parts by weight of 4,4'-diaminodiphenylamine with weighing paper, add to the beaker, shake. Observe the solid dissolution, if there are undissolved solids, add an appropriate amount of DMF solvent, shake until the solid is completely dissolved, and record the amount of solvent added. Accurately weigh 31 parts by weight of diethylenetriamine, drop into the beaker, use a clean dropper, stir for 1-2 min, mix evenly. Add to the silica gel mold, vacuum degassing for 10 min, then transfer to a 60℃ flat plate heater until the sample gel, then transfer to a 100℃ oven for 4h to continue the reaction, to obtain a repairable thermosetting resin containing Schiff base type dynamic covalent bonds.

[0068] The polyimide resins containing Schiff base-type dynamic covalent bonds prepared in Example 2 and Comparative Example 1 were characterized by infrared spectroscopy. The characterization results are as follows: Figure 2 As shown. By Figure 2 It can be known that 1645cm -1 The peak at 1702 cm⁻¹ represents the newly formed C=N imine bond. -1 The peak at 3300–3500 cm⁻¹ should be the stretching absorption band of the C=O bond in terephthalaldehyde, appearing as a shoulder peak; -1 No characteristic peak of -NH2 was observed. Therefore, it can be concluded that the Schiff base-type dynamic covalent bonds prepared in Example 2 and Comparative Example 1 contain a large number of imine bonds, i.e., Schiff base-type dynamic covalent bonds.

[0069] The polyimide resin containing Schiff base-type dynamic covalent bonds prepared in Example 1 was cut into segments (e.g. Figure 3 As shown in the figure, a self-healing remodeling experiment was conducted at 5 MPa and 100℃. After 30 minutes, the sample showed... Figure 4 As shown. By Figure 4 It can be seen that the polyimide resin containing Schiff base-type dynamic covalent bonds, after being cut into segments, is reshaped into a whole. Therefore, the polyimide resin containing Schiff base-type dynamic covalent bonds prepared in this invention has a self-healing function.

[0070] The polyimide resins containing Schiff base-type dynamic covalent bonds prepared in Examples 1-9 and Comparative Example 1 were subjected to DMA testing in tensile mode. The test temperature range was from -30°C to 120°C, and the heating rate was 10 K·min. -1 The test frequency was 1Hz. The results of Examples 1-3 and Comparative Example 1 are as follows: Figures 5 to 7 As shown. Figure 5 The graph shows the storage modulus (E′) curves of the polyimide resins containing Schiff base-type dynamic covalent bonds prepared in Examples 1-3 and Comparative Example 1. E′ refers to the amount of energy stored due to elastic deformation (reversible deformation) when the material undergoes deformation. The storage modulus E′ is an important indicator for measuring the rigidity and elasticity of polymer materials. Figure 6 The graph shows the loss modulus (E″) curves of the polyimide resins containing Schiff base-type dynamic covalent bonds prepared in Examples 1-3 and Comparative Example 1. E″ refers to the amount of energy lost due to viscous deformation (irreversible deformation) when the material undergoes deformation. The loss modulus E″ is an important indicator for measuring the viscosity of polymer materials. Figure 7 The graphs show the loss factor curves of the polyimide resins containing Schiff base-type dynamic covalent bonds prepared in Examples 1-3 and Comparative Example 1, where tanδ = E″ / E′, and the temperature corresponding to the peak value on the loss factor tanδ curve is T. g .

[0071] according to Figures 5 to 7It can be seen that at lower temperature (glassy state), the molecular chain segment is in frozen state, and the thermal motion ability is low, only small unit can move, at this time, the relaxation time of chain segment movement is far greater than the experimental test time range, in macroscopically, it is shown that the material has small deformation when stressed, and the storage modulus is high. With the increase of temperature, the thermal motion ability of molecules is gradually enhanced, at this time, the chain segment has sufficient time to move, and the storage modulus rapidly decreases, but due to the restriction of three-dimensional network crosslinking point, it presents rubbery state. The transition zone in the middle is glass transition.

[0072] It can be seen from the comparison of examples 1-3 and comparative example 1 that the storage modulus of examples 1-3 is significantly higher than that of comparative example 1 after introducing 4,4'-diamino diphenyl ether into the system, which shows that the rigidity and elasticity of the material are enhanced. Since the other parameters of the test sample and the test parameters are all consistent, the strength and rigidity of the material are positively correlated, and the strength is also enhanced. It can be seen from the comparison of examples 1-3 and comparative example 1 that comparative example 1 only contains substituted imine, and the structure is unstable. After introducing 4,4'-diamino diphenyl ether into the system in the application, at least one aryl group is connected to the carbon atom or the nitrogen atom of the carbon-nitrogen double bond, forming a large conjugated structure, which is more stable, so the strength of the material is enhanced. Therefore, it can be seen that the polyimine resin containing Schiff base type dynamic covalent bond prepared by the application has better mechanical properties.

[0073] Table 1 is the glass transition temperature of the polyimine resin containing Schiff base type dynamic covalent bond prepared in examples 1-9 and comparative example 1, which is the temperature corresponding to the peak on the tanδ curve graph T g The increase of glass transition temperature indirectly represents that the temperature range that the material can be used is improved. It can be seen from table 1 that the glass transition temperature of the polyimine resin containing Schiff base type dynamic covalent bond prepared in examples 1-9 is improved, which represents that the temperature range that the polyimine resin containing Schiff base type dynamic covalent bond can be used is improved, that is, the heat resistance is improved.

[0074] Table 1 glass transition temperature of the polyimine resin containing Schiff base type dynamic covalent bond prepared in examples 1-9 and comparative example 1

[0075] Glass transition temperature / °C Example 1 36.58 Example 2 38.09 Example 3 38.83 Example 4 37.27 Example 5 37.49 Example 6 32.16 Example 7 35.02 Example 8 33.87 Example 9 34.43 Comparative Example 1 21.54

Claims

1. A reworkable thermoset material containing a Schiff base type dynamic covalent bond, characterized in that: The repairable thermoset material is prepared from raw materials comprising the following components: Each component is in parts by weight, The diamine is a di-functional polyether amine; the triamine is a tri-functional polyether amine.

2. The repairable thermoset material according to claim 1, wherein: The di-functional polyether amine is any one of D230, D400, D2000, D4000.

3. The repairable thermoset material according to claim 1, wherein: The tri-functional polyether amine is T403 or T5000.

4. The repairable thermoset material according to claim 1, wherein: The ratio of the total moles of the diamine and the 4,4'-diamino diphenyl ether to the moles of the triamine is 1:0.3-6; or The ratio of the total moles of the diamine and the 4,4'-diamino diphenyl ether to the moles of the triamine is 1:0.3-6.

5. The repairable thermoset material according to claim 1, wherein: The molar ratio of the diamine to the 4,4'-diamino diphenyl ether is 1:0.5-2, or The molar ratio of the diamine to the 4,4'-diamino diphenyl ether is 1:0.5-2.

6. The restorable thermoset material of claim 1, wherein: The solvent is N,N-dimethylformamide or ethanol.

7. A process for the preparation of a recoverable thermoset material containing a Schiff base type dynamic covalent bond according to one of claims 1 to 6, characterized in that The method comprises: dissolving 4,4'-diamino diphenyl ether or 4,4'-diamino diphenylamine, terephthaldehyde, diamine, triamine in a solvent, heating, and obtaining a repairable thermoset material containing Schiff base type dynamic covalent bonds after reaction.

8. The method according to claim 7, wherein: The reaction temperature is 80-100 ℃; and / or The reaction time is 4-10 h.

9. Use of the repairable thermoset material containing Schiff base type dynamic covalent bonds according to any one of claims 1-6 or the repairable thermoset material containing Schiff base type dynamic covalent bonds obtained by the method according to any one of claims 7-8 in sports goods, aviation, automobiles, wind energy, and gas storage pressure vessels.

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