Heat-resistant self-repairing polyurethane elastic system and preparation method thereof

Abstract

The invention discloses a heat-resistant self-repairing polyurethane elastic system and a preparation method thereof. The preparation method comprises the following steps: by taking 3, 3 '-diaminobenzidine (DAB) and 3, 3', 4, 4 '-benzophenone tetracarboxylic dianhydride (BDTA) as raw materials, reacting in a first solvent to obtain a DTA solution; then adding a diisocyanate compound, and reacting to obtain a DTA-NCO solution; and adding a second solvent, a polyol compound and a catalyst, carrying out prepolymerization reaction, and carrying out heat treatment to obtain the heat-resistant high-strength self-repairing polyurethane system. Compared with an existing similar self-repairing polyurethane elastomer system, the product has excellent mechanical properties, outstanding heat resistance and high self-repairing behavior, the high-temperature usability and safety of the self-repairing polyurethane elastomer system are greatly improved, and application of the self-repairing polyurethane elastomer system in the aspect of advanced materials such as aerospace is facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of polyurethane systems, and particularly relates to a heat-resistant self-healing polyurethane elastomer system and a preparation method thereof. Background Art

[0002] Polyurethane elastomer materials are widely used in fields such as automobiles, aerospace, flexible electronics, and medical due to their excellent ductility, chemical resistance, and wear resistance. However, a large amount of waste polyurethane materials often cause serious environmental pollution and resource waste problems. Developing polyurethane materials with self-healing functions can effectively solve the above problems. In recent years, self-healing polyurethane elastomer systems based on non-covalent bond interactions have shown great application potential in fields such as coatings, foams, automobiles, biomedicine, and electronic devices. Although self-healing polyurethane elastomer systems based on non-covalent bond interactions can exhibit excellent mechanical properties and high self-healing efficiency under mild environments, with the complexity and variability of the material application environment, such self-healing polyurethane systems can no longer meet the performance development requirements due to poor heat resistance and generally low mechanical properties.

[0003] CN119798743A provides a self-healing polyurethane film containing disulfide bonds and DA bonds and a preparation method thereof, including the following steps: (1) adding an organic solvent into a three-necked flask, then dissolving a diol, a diisocyanate, a disulfide bond monomer, and a DA bond-forming monomer one in the organic solvent, and then adding a catalyst and mechanically stirring evenly; (2) introducing nitrogen into the three-necked flask to evacuate air, setting the reaction temperature, and reacting under mechanical stirring; (3) dropping a DA bond-forming monomer two into the solution obtained after the reaction in step (2) under a nitrogen environment. After the dropping of the DA bond-forming monomer two is completed, set the reaction temperature and react for a period of time; (4) pouring the solution obtained after the reaction in step (3) into a polytetrafluoroethylene mold, drying to obtain a self-healing polyurethane film, the tensile strength of the film is 31 MPa, and the repair rate is 83%. CN119798599A discloses a self-healing aqueous polyurethane and a preparation method and application thereof, which are prepared by reacting the following raw materials: polyisocyanate, macromolecular polyol, small molecule chain extender, carboxylic acid-type hydrophilic compound, amino-containing compound, neutralizing agent, water, catalyst; the provided aqueous polyurethane has a repair rate of about 95% after 40 °C for 8 h. CN119751935A discloses a preparation method and application of a degradable and fluorescent self-healing polyurethane film. Dissolve o-phenylenediamine and tryptophan in a solvent, add an acid solution and deionized water, dissolve to obtain a mixed solution, transfer the mixed solution to a Teflon-lined autoclave for reaction to obtain carbon quantum dots; (2) use isocyanate, polyol and a dispersion solvent as raw materials, add an organotin catalyst, and then add a chain extender to react to obtain a polyurethane solution; (3) add carbon quantum dots to the polyurethane solution, stir and cast the solution onto a polytetrafluoroethylene substrate for self-leveling and drying to obtain a degradable and fluorescent self-healing polyurethane film, and its self-healing efficiency is low. CN119431720A discloses a polyurethane with multi-dynamic bond synergistic self-healing and a preparation method thereof. The raw material composition includes polyglycol, diisocyanate, pyridine-based chain extender, catechol, and trivalent iron ion salt, and the self-healing efficiency of its product is about 90%.

[0004] Therefore, it is of greater social value and economic benefit to develop a self-healing polyurethane elastomer system with high strength, heat resistance and strong applicability. Summary of the Invention

[0005] Aiming at the problems of poor heat resistance and low mechanical properties in the existing non-covalent bond self-healing polyurethane elastomer system, the present invention uses 3,3'-diaminobenzidine (DAB) and 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BDTA) as raw materials, combines diisocyanate compounds and polyol compounds, and improves the heat resistance and self-healing performance of the system through the use of solvents, especially showing excellent mechanical strength and self-healing performance (~100%), which is unexpected to those skilled in the art.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows.

[0007] A heat-resistant self-healing polyurethane elastic system and a preparation method thereof, comprising the following steps: using DAB and BDTA as raw materials, reacting in a first solvent to obtain a DTA solution; then adding a diisocyanate compound and reacting to obtain a DTA-NCO solution; then adding a second solvent, a polyol compound and a catalyst, carrying out a prepolymerization reaction and then heat treatment to obtain a heat-resistant self-healing polyurethane elastic system; the molar ratio of DAB, BDTA, the diisocyanate compound, the polyol compound, the catalyst, the first solvent, and the second solvent is 2:(0.8 - 1.2):(15 - 20):(1.25 - 3.25):(0.01 - 0.05):(100 - 160):(100 - 150).

[0008] In the present invention, when reacting in the first solvent, the reaction temperature is 80 - 100 °C and the time is 0.5 - 2 hours (h) to obtain an oligomer (DTA) solution, and the reaction temperature is 90 - 110 °C and the time is 0.5 - 2 h to obtain a DTA-NCO solution; in the second solvent, when carrying out the prepolymerization reaction, the reaction temperature is 70 - 90 °C and the time is 0.5 - 2 h; the heat treatment process is 40 - 60 °C / 10 - 15 h + 80 - 100 °C / 4 - 6 h.

[0009] Preferably, the molar ratio of DAB, BDTA, the diisocyanate compound, the polyol compound, the catalyst, the first solvent, and the second solvent is 2:1:16:(1.25 - 3.25):(0.01 - 0.05):(100 - 160):(100 - 150). The low-temperature glass transition temperature of the above heat-resistant self-healing polyurethane elastic system of the present invention is less than -35 °C, and the high-temperature glass transition temperature is greater than 205 °C. Preferably, the material prepared by the present invention has obvious glass transition temperatures at both ultra-low temperature (-52 °C) and ultra-high temperature (226 °C), a high thermal decomposition temperature, and at the same time exhibits excellent mechanical strength and self-healing performance (~100%).

[0010] In the present invention, the first solvent and the second solvent are independently selected from one or more of N,N-dimethylformamide, acetone, and ethanol; the catalyst includes one or more of organotin and organolead.

[0011] The present invention discloses a polyurethane elastomer material, the preparation raw materials of which include the above heat-resistant self-healing polyurethane elastic system.

[0012] The present invention discloses the application of the above heat-resistant self-healing polyurethane elastic system in the preparation of polyurethane materials.

[0013] The present invention discloses the application of the above heat-resistant self-healing polyurethane elastic system in the preparation of self-healing materials.

[0014] The present invention discloses the application of the above heat-resistant self-healing polyurethane elastic system in the preparation of aerospace materials.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: on the premise that the urethane elastomer of the present invention has both high strength and high self-healing performance, it not only has an ultra-low temperature T g (-52 °C), but also has an ultra-high temperature T g (~226 °C) and a high initial thermal decomposition temperature (~314 °C), and has the performance of being used in both low-temperature and ultra-high-temperature environments. Description of the Drawings

[0016] Figure 1 It is the FTIR spectra of DTA-NCO, PTMEG, HDI and the sample of Example 1.

[0017] Figure 2 It is the UV-vis absorption diagram of the sample of Example 1.

[0018] Figure 3 It is the photos of the scratched sample of Example 1 before and after heat treatment at 180 °C for 2 h and the scratched samples of Comparative Example 1-1 before and after heat treatment at 180 °C and 140 °C for 2 h respectively, where (a) is the photo of the sample of Example 1, and (b) and (c) are the photos of the samples of Comparative Example 1.

[0019] Figure 4 It is the photos of the scratched sample of the control example before and after heat treatment at 180 °C for 2 h.

[0020] Figure 5 It is the photos of the scratched sample of Example 2 before and after heat treatment at 160 °C for 2 h.

[0021] Figure 6 It is the photos of the scratched sample of Example 3 before and after heat treatment at 140 °C for 2 h.

[0022] Figure 7 It is the photos of the scratched sample of Example 4 before and after heat treatment at 160 °C for 2 h.

[0023] Figure 8 It is the photos of the scratched sample of Example 5 before and after heat treatment at 160 °C for 2 h. Detailed Embodiments

[0024] In the present invention, DAB and BDTA are respectively dissolved in a first solvent, and then the BDTA solution is dropped into the DAB solution, and reacted at 90 °C for 0.5 - 2 hours (h) to obtain a DTA solution; subsequently, a diisocyanate compound is dropped into the DTA solution, and reacted at 100 °C for 0.5 - 1 h to obtain a DTA-NCO solution; then a second solvent, a polyol compound and a catalyst are added, and reacted at 80 °C for 0.5 - 2 h under nitrogen protection, and then the solution is cast into a mold, and heat-treated at 50 °C / 12 h + 80 - 100 °C / 4 - 6 h to obtain a heat-resistant self-healing polyurethane elastomer system film. Wherein the molar ratio of DAB:BDTA:diisocyanate compound:polyol compound:catalyst:first solvent:second solvent is 2:1:16:(1.25 - 3.25):(0.01 - 0.05):(100 - 160):(100 - 150).

[0025] In the present invention, the polyol includes one or more of polyether polyol and polyester polyol; the diisocyanate compound includes one or more of isophorone diisocyanate (IPDI), toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate (HDI), lysine diisocyanate; the solvent is one or a mixture of N,N-dimethylformamide (DMF), acetone, and ethanol; the catalyst is one or more of organotin (such as dibutyltin dilaurate, stannous octoate, etc.) and organolead (such as tetraethyllead and triethyllead).

[0026] In the present invention, the heat-resistant self-healing polyurethane elastomer system has obvious glass transition temperatures of both ultra-low temperature (-52 °C) and ultra-high temperature (226 °C), a high thermal decomposition temperature, and at the same time exhibits excellent mechanical strength and self-healing performance (~100%).

[0027] The following illustrates the technical progress of the present invention through specific experiments. The raw materials used are all existing products, and the specific preparation operations and performance tests are all conventional techniques; unless otherwise specified, the molecular weight index is the average molecular weight.

[0028] Example 1 Dissolve 3,3'-diaminobenzidine DAB (2 mmol) and 3,3',4,4'-benzophenone tetracarboxylic dianhydride BDTA (1 mmol) in DMF (the first solvent, 60 mmol each) solvent respectively, then drop the BDTA solution into the DAB solution, and react at 90 °C for 1.5 h to obtain a DTA solution; subsequently, drop hexamethylene diisocyanate HDI (16 mmol) into the DTA solution, and react at 100 °C for 0.5 h to obtain a DTA-NCO solution; then add DMF (the second solvent, 130 mmol), polytetrahydrofuran PTMEG-2000 with a molecular weight of 2000 (1.25 mmol) and dibutyltin dilaurate DBTDL (0.04 mmol) at room temperature, and react at 80 °C for 2 h under nitrogen protection, and then pour the solution into a mold (conventional method), and heat-treat at 50 °C / 12 h + 80 °C / 6 h to obtain a polyurethane elastomer (PUE-DTA) film; where the molar ratio of DAB:BDTA:diisocyanate compound:polyol compound:first solvent:second solvent is 2:1:16:1.25:120:130.

[0029] Comparative Example 1-1 Mix HDI (16 mmol), DMF (130 mmol), polytetrahydrofuran PTMEG-2000 (1.25 mmol) and DBTDL (0.04 mmol), react at 80 °C for 2 h under nitrogen protection, and then pour the solution into a mold, and heat-treat at 50 °C / 12 h + 80 °C / 6 h to obtain a polyurethane film.

[0030] Comparative Example 1-2 Dissolve DAB (2 mmol) in DMF (the first solvent, 60 mmol) solvent, then add hexamethylene diisocyanate HDI (16 mmol), and react at 100 °C for 0.5 h; then add DMF (the second solvent, 130 mmol), polytetrahydrofuran PTMEG-2000 with a molecular weight of 2000 (1.25 mmol) and dibutyltin dilaurate DBTDL (0.04 mmol) at room temperature, and react at 80 °C for 2 h under nitrogen protection, and then pour the solution into a mold (conventional method), and heat-treat at 50 °C / 12 h + 80 °C / 6 h to obtain a polymer film; where the molar ratio of DAB:diisocyanate compound:polyol compound:first solvent:second solvent is 2:16:1.25:60:130.

[0031] Comparative Example 1-3 Dissolve BDTA (1 mmol) in DMF (the first solvent, 60 mmol), then add hexamethylene diisocyanate HDI (16 mmol), and react at 100 °C for 0.5 h; then add DMF (the second solvent, 130 mmol), polytetramethylene ether glycol PTMEG-2000 with a molecular weight of 2000 (1.25 mmol), and dibutyltin dilaurate DBTDL (0.04 mmol) at room temperature, react at 80 °C for 2 h under nitrogen protection, and then pour the solution into a mold (conventional method), and obtain a polyurethane elastomer film through heat treatment at 50 °C / 12 h + 80 °C / 6 h; the molar ratio of BDTA:diisocyanate compound:polyol compound:first solvent:second solvent is 1:16:1.25:60:130.

[0032] Infrared (FTIR) spectral data of BDTA: 3100 - 3700 cm -1 : N-H stretching vibration in -NH2; 1500 cm -1 : C=C stretching vibration in the benzene ring; 1650 cm -1 and 1720 cm -1 : C=O stretching vibration in imide (-CONCO-); 1384 cm -1 : C-N stretching vibration.

[0033] Figure 1 are the FTIR spectra of DTA-NCO, PTMEG, HDI and the sample of Example 1; Figure 2 is the UV-vis absorption diagram of the sample of Example 1. When DTA reacts with HDI, there is no obvious -NH2 characteristic peak in its product DTA-NCO, and a weak -NH characteristic absorption peak appears at 3326 cm -1 and a -NCO characteristic peak appears at 2260 cm -1 , and an absorption peak of C=O in urea (-NHCONH-) appears at 1620 cm -1 . The above phenomena indicate that -NH2 in DTA reacts with -NCO in HDI, and -NCO-functionalized DTA is successful. When DTA-NCO reacts with PTMEG, there is no -NCO characteristic absorption peak in the product PUE-DTA at 2260 cm -1 , and no -OH characteristic peak appears at 3459 cm -1 , and the C=O stretching vibration peak at 1780 - 1600 cm -1 is enhanced, indicating that -NCO reacts with -OH to form -NHCOO- groups. The UV-vis absorption diagram of the sample of Example 1 shows that its maximum absorption wavelength is 523 nm, indicating that there is a π→π* electronic transition in the sample of Example 1, which is mainly due to the benzene ring structure in the sample.

[0034] Table 1 presents the mechanical properties, thermal performance parameters, and scratch self-healing efficiency after heat treatment at 180°C for 2 h of the samples in Example 1 and Comparative Example. Figure 3 The photos before and after heat treatment at 180°C for 2 h of the scratched sample in Example 1 and the scratched sample in Comparative Example 1-1 at 180°C and 140°C for 2 h are shown. The tensile strength of the sample in Example 1 is 34 MPa, and the elongation at break is 213%. Compared with the Comparative Example, the sample in Example 1 has a significantly higher tensile strength, which is 183% higher than that of the sample in Comparative Example 1-1. The system in Example 1 has three glass transition temperatures (T g ), which are -54°C, 149°C, and 226°C, respectively. The sample in Example 1 not only has a low-temperature T g , but also obviously has two more high-temperature T g than Comparative Example 1-1, which means that the system of the present invention has both low-temperature and high-temperature usability. In particular, Comparative Example 1-1 has only one low-temperature T g , resulting in poor self-healing ability and difficulty in high-temperature industrial applications. The thermal decomposition temperature (T d5 ) and the temperature of the maximum thermal decomposition rate (T dmax ) of the sample in Example 1 when the weight loss is 5 wt% are 308°C and 414°C, respectively, which are 33°C and 40°C higher than those in Comparative Example 1-1, respectively. The surface scratches of the sample in Example 1 can be completely healed after heat treatment at 180°C for 2 h ( Figure 3 (a)), and its self-healing efficiency is 100%. After heat treatment at 180°C for 2 h of the sample in Comparative Example 1-1, the sample melts ( Figure 3 (b)). Even if the sample is heat-treated at 140°C for 2 h ( Figure 3 (c)), the surface scratches still cannot heal well. It can be seen that the complete healing of the sample in Example 1 overcomes the technical prejudice in the prior art that it is difficult for heat-resistant polyurethane self-healing materials to achieve complete repair.

[0035] Table 1 Mechanical properties, thermal performance parameters, and scratch self-healing efficiency of the samples in Example 1 and Comparative Example

[0036] Control Example Dissolve 3,3'-diaminobenzidine DAB (2 mmol) and 3,3',4,4'-benzophenone tetracarboxylic dianhydride BDTA (1 mmol) in DMF (60 mmol) solvent respectively. Then, add the 3,3',4,4'-benzophenone tetracarboxylic dianhydride solution dropwise to the 3,3'-diaminobenzidine solution and react at 90 °C for 1.5 h to obtain an oligomer (DTA) solution. Then, add DMF (130 mmol) and HDI (59 mmol) dropwise and react at 100 °C for 1.5 h to obtain an -NCO functionalized DTA solution. Then, add DMF (260 mmol), polytetrahydrofuran PTMEG-2000 (8 mmol) and DBTDL (0.04 mmol) at room temperature and react at 80 °C for 2 h under nitrogen protection to obtain a prepolymer solution. Cast the solution into a conventional casting mold and heat-treat it at 50 °C / 12 h + 80 °C / 6 h to obtain a polyurethane elastomer film. Figure 4 Photographs of the scratched sample in the comparative example before and after heat treatment at 180 °C for 2 h. After heat treatment at 180 °C for 2 h, the surface scratch of the comparative example sample became narrower but was still visible. The self-healing efficiency of the sample was 48% and it could not be completely healed. The molar ratio of 3,3'-diaminobenzidine: 3,3',4,4'-benzophenone tetracarboxylic dianhydride: diisocyanate compound: polyol compound: catalyst was 2:1:59:8:0.04.

[0037] Example 2 Refer to Example 1, the difference is that 2.25 mmol of polytetrahydrofuran PTMEG-2000 with a molecular weight of 2000 is used, and the rest is the same, to obtain a film, that is, the molar ratio of DAB: BDTA: diisocyanate compound: polyol compound: first solvent: second solvent is 2:1:16:2.25:120:130.

[0038] Comparative Example 2 Refer to Comparative Example 1-1, the difference is that 2.25 mmol of polytetrahydrofuran PTMEG with a molecular weight of 2000 is used, and the rest is the same, to obtain a film.

[0039] Table 2 shows the mechanical properties, thermal performance parameters and scratch self-healing efficiency after heat treatment at 160 °C for 2 h of the samples in Example 2 and Comparative Example 2. Figure 5 Photographs of the scratched sample in Example 2 before and after heat treatment at 160 °C for 2 h. The tensile strength of the system in Example 2 was 31 MPa and the elongation at break was 276%. Compared with Comparative Example 2, Example 2 had a higher tensile strength, which was 78% higher. The system in Example 2 had three glass transition temperatures (T g ), which were -54 °C, 168 °C and 226 °C respectively. The system in Example 2 not only had a low T g , but also obviously had two more high-temperature Ts than Comparative Example 2g , which means that the system of the present invention has both low-temperature and high-temperature usability. In Example 2, the thermal decomposition temperature (T d5 ) and the maximum thermal decomposition rate temperature (T dmax ) at 5 wt% weight loss are 313 °C and 411 °C respectively, which are 37 °C and 35 °C higher than those of Comparative Example 2 respectively. The scratches on the surface of the sample in Example 2 can be completely healed after heat treatment at 160 °C for 2 h, and its self-healing efficiency is 100%.

[0040] Table 2 Mechanical properties, thermal performance parameters and scratch self-healing efficiency of the samples of Example 2 and Comparative Example 2

[0041] Example 3 Referring to Example 1, the difference is that 3.25 mmol of polytetrahydrofuran PTMEG-2000 with a molecular weight of 2000 is used, and the rest is the same, and a film is obtained. That is, the molar ratio of DAB:BDTA:diisocyanate compound:polyol compound:first solvent:second solvent is 2:1:16:3.25:120:130, and the calculated hydrogen bond content is 41%.

[0042] Comparative Example 3 Referring to Comparative Example 1-1, the difference is that 3.25 mmol of polytetrahydrofuran PTMEG-2000 with a molecular weight of 2000 is used, and the rest is the same, and a film is obtained.

[0043] Table 3 shows the mechanical properties, thermal performance parameters and scratch self-healing efficiency of the samples of Example 3 and Comparative Example 3 after heat treatment at 140 °C for 2 h. Figure 6 The photos of the scratched sample in Example 3 before and after heat treatment at 140 °C for 2 h are shown. The tensile strength of the system in Example 3 is 34 MPa, and the elongation at break is 307%. Compared with Comparative Example 3, Example 3 has a higher tensile strength, which is 35% higher. The system in Example 3 has three glass transition temperatures (T g ), which are -54 °C, 149 °C and 224 °C respectively. The system in Example 3 not only has a low-temperature T g , but also obviously has two more high-temperature T g than Comparative Example 3, which means that the system of the present invention has both low-temperature and high-temperature usability. In Example 3, the thermal decomposition temperature (T d5 ) and the maximum thermal decomposition rate temperature (T dmax ) at 5 wt% weight loss are 314 °C and 408 °C respectively, which are 41 °C and 31 °C higher than those of Comparative Example 3 respectively. The scratches on the surface of the sample in Example 3 can be completely healed after heat treatment at 140 °C for 2 h, and its self-healing efficiency is 100%.

[0044] Table 3 Mechanical properties, thermal properties and scratch self-healing efficiency of the samples in Example 3 and Comparative Example 3

[0045] Example 4 Dissolve DAB (2 mmol) and BDTA (1 mmol) in DMF (50 mmol each) solvent respectively, then drop the BDTA solution into the DAB solution, and react at 90 °C for 0.5 h to obtain a DTA solution; subsequently, drop IPDI (16 mmol) into the DTA solution and react at 100 °C for 0.5 h to obtain a DTA-NCO solution; then add DMF (100 mmol), polyether polyol JX230 with a number average molecular weight of 2800 (2.25 mmol), and DBTDL (0.01 mmol) at room temperature, and react at 80 °C for 0.5 h under nitrogen protection, and then pour the solution into a mold, and heat-treat at 50 °C / 12 h + 100 °C / 4 h to obtain a polyurethane film, and the hydrogen bond content is calculated to be 52%. Among them, the molar ratio of DAB:BDTA:diisocyanate compound:polyol compound:catalyst:first solvent:second solvent is 2:1:16:2.25:0.01:100:100.

[0046] Comparative Example 4 Add IPDI (16 mmol), DMF (100 mmol), polyether polyol JX230 with a number average molecular weight of 2800 (2.25 mmol), and DBTDL (0.01 mmol), heat up to 80 °C and react for 2 h under nitrogen protection, and then pour the solution into a mold, and heat-treat at 50 °C / 12 h + 80 °C / 6 h to obtain a polyurethane system film.

[0047] Table 4 shows the mechanical properties, thermal properties and scratch self-healing efficiency of the samples in Example 4 and Comparative Example 4 after heat treatment at 160 °C for 2 h. Figure 7 The photos of the scratched sample in Example 4 before and after heat treatment at 160 °C for 2 h are shown. The tensile strength of the system in Example 4 is 18 MPa, and the elongation at break is 356%. Compared with Comparative Example 4, Example 4 has a higher tensile strength, which is 157% higher. The system in Example 4 has three glass transition temperatures (T g ), which are -42 °C, 175 °C and 210 °C respectively. The system in Example 4 not only has a low T g , but also obviously has two more high-temperature Ts than Comparative Example 4 g , which means that the system of the present invention has both low-temperature and high-temperature usability. The thermal decomposition temperature (T d5 ) and the maximum thermal decomposition rate temperature (T dmax)(They are) 279 °C and 356 °C respectively, which are 47 °C and 64 °C higher than those of Comparative Example 4 respectively. The self-healing efficiency of the surface scratches of the sample in Example 4 was 100% after heat treatment at 160 °C for 2 h.

[0048] Table 4 Mechanical properties, thermal performance parameters and scratch self-healing efficiency of the samples of Example 4 and Comparative Example 4

[0049] Example 5 Dissolve DAB (2 mmol) and BDTA (1 mmol) in DMF (80 mmol each) respectively, then drop the BDTA solution into the DAB solution, and react at 90 °C for 2 h to obtain a DTA solution; then drop IPDI (12 mmol) and diphenylmethane diisocyanate (4 mmol) into the DTA solution, and react at 100 °C for 1 h to obtain a DTA-NCO solution. Then add DMF (100 mmol), acetone (50 mmol), polyether polyol with a number average molecular weight of 2800 (2.5 mmol), and DBTDL (0.05 mmol) at room temperature, and react at 80 °C for 2 h under nitrogen protection. Then pour the solution into a mold and heat-treat it at 50 °C / 12 h + 100 °C / 6 h to obtain a polyurethane film, where the molar ratio of DAB:BDTA:diisocyanate compound:polyol compound:catalyst:first solvent:second solvent is 2:1:16:2.5:0.05:160:150.

[0050] Comparative Example 5 Add IPDI (12 mmol), diphenylmethane diisocyanate (4 mmol), DMF (100 mmol), acetone (50 mmol), polyether polyol with a number average molecular weight of 2800 (2.5 mmol), and DBTDL (0.05 mmol), heat up to 80 °C under nitrogen protection and react for 2 h, then pour the solution into a mold and heat-treat it at 50 °C / 12 h + 100 °C / 6 h to obtain a polyurethane system film.

[0051] Table 5 gives the mechanical properties, thermal performance parameters of the samples of Example 5 and Comparative Example 5 and the scratch self-healing efficiency after heat treatment at 160 °C for 2 h. Figure 8 The photos of the scratched sample in Example 5 before and after heat treatment at 160 °C for 2 h. The tensile strength of the system in Example 5 was 21 MPa, and the elongation at break was 332%. Compared with Comparative Example 5, Example 5 had a higher tensile strength, which was 110% higher. The system in Example 5 had three glass transition temperatures (T g ), which were -37 °C, 179 °C and 220 °C respectively. The system in Example 5 not only had a low T g , but also obviously had two more high-temperature Ts than Comparative Example 5g , which means that the system of the present invention has both low-temperature and high-temperature usability. In Example 5, the thermal decomposition temperature (T d5 ), and the maximum thermal decomposition rate temperature (T dmax ), are 285°C and 361°C respectively, which are 49°C and 59°C higher than those of Comparative Example 5 respectively. The self-healing efficiency of the scratch on the surface of the sample in Example 5 is 100% after heat treatment at 160°C for 2 h.

[0052] Table 5 Mechanical properties, thermal properties parameters and scratch self-healing efficiency of the samples of Example 5 and Comparative Example 5

[0053] In the present invention, the sample performance tests are as follows: The 5wt% weight loss temperature (T d5 ), and the thermal decomposition temperature of the maximum thermal weight loss rate (T dmax ), are measured by a thermogravimetric analyzer (Discovery, TGA550, TA Instruments, USA) under a nitrogen atmosphere with a heating rate of 10°C / min.

[0054] The glass transition temperature T g is measured by a dynamic thermomechanical analyzer (DMA, Q850, TA Instruments, USA) using the film tensile mode, with a frequency of 1 Hz, a heating rate of 3°C / min, and a sample size of 30 mm × 5 mm × 1 mm.

[0055] The tensile properties are tested on dumbbell-shaped samples using an electronic universal mechanical testing machine (Z005-TH), with a sample size of 115 mm × 6 mm × 1 mm and a loading rate of 50 mm / min.

[0056] The self-healing efficiency is defined as the percentage of the healed scratch width to the initial scratch width after the scratch width on the sample surface heals for 2 h after natural placement at a certain environmental temperature (140 - 180°C). The scratch on the sample surface is made with a blade having a thickness of 0.28 mm, and the depth is controlled at 0.5 mm.

[0057] Among the polyurethane elastomers reported so far, the T g of most polyurethane elastomer systems is lower than 100°C, and the self-healing efficiency is also mostly lower than 100%. For example, in the prior art, a self-healing polyurethane elastomer containing the synergistic action of imine bonds and hydrogen bonds was constructed, with a tensile strength of 4 - 7.5 MPa, an elongation at break of 275 - 250%, a Tg of 25.4 - 38.8°C, and a T d5It is 287.7~316.9 °C. Due to the existence of dynamic imine bonds and hydrogen bonds, after the elastomer specimen is cut and heated at 80 °C for 24 h, the repair efficiency of its tensile strength can reach 42.6%. The existing technology constructs a self-healing polyurethane elastomer by introducing multiple hydrogen bonds and disulfide bonds. Its tensile strength is 17.9 MPa, and the elongation at break is 320%. T g It is 68.5 °C. The existing technology constructs a polyurethane elastomer with the synergistic action of disulfide bonds and hydrogen bonds. Its tensile strength is 5~21 MPa, T g It is 10.7~80.2 °C. The existing literature shows that although introducing dynamic reversible covalent bonds and other non-covalent bond interactions into the non-covalent bond constructed polyurethane self-healing system can improve the strength and heat resistance of polyurethane to a certain extent, it is difficult to meet the application requirements of self-healing polyurethane elastomers in high-temperature environments. Therefore, the preparation of high-strength self-healing polyurethane elastomers suitable for higher temperatures has great economic significance. At present, there are few reports on elastomers with high Tg (higher than 140 °C). On the premise of having both high strength and high self-healing performance, the urethane elastomer of the present invention not only has an ultra-low temperature T g (-52 °C), but also has an ultra-high temperature T g (~226 °C) and a high initial thermal decomposition temperature (~314 °C), and has the performance of being used in both low-temperature and ultra-high temperature environments.

Claims

1. A preparation method of a heat-resistant self-healing polyurethane elastic system, characterized in that, It includes the following steps: using DAB and BDTA as raw materials, reacting in a first solvent to obtain a DTA solution; then adding a diisocyanate compound and reacting to obtain a DTA-NCO solution; further adding a second solvent, a polyol compound and a catalyst, carrying out a prepolymerization reaction and then heat treatment to obtain a heat-resistant and high-strength self-healing polyurethane system; the molar ratio of DAB, BDTA, the diisocyanate compound, the polyol compound, the catalyst, the first solvent and the second solvent is 2:(0.8 - 1.2):(15 - 20):(1.25 - 3.25):(0.01 - 0.05):(100 - 160):(100 - 150).

2. The preparation method of the heat-resistant self-healing polyurethane elastic system according to claim 1, characterized in that, When reacting in the first solvent, the reaction temperature is 80 - 100 °C and the time is 0.5 - 2 h to obtain the DTA solution, and the reaction temperature is 90 - 110 °C and the time is 0.5 - 2 h to obtain the DTA-NCO solution; in the second solvent, when carrying out the prepolymerization reaction, the reaction temperature is 70 - 90 °C and the time is 0.5 - 2 h; the heat treatment process is 40 - 60 °C / 10 - 15 h + 80 - 100 °C / 4 - 6 h.

3. The preparation method of the heat-resistant self-healing polyurethane elastic system according to claim 1, characterized in that, The molar ratio of DAB, BDTA, the diisocyanate compound, the polyol compound, the catalyst, the first solvent and the second solvent is 2:1:16:(1.25 - 3.25):(0.01 - 0.05):(100 - 160):(100 - 150).

4. The preparation method of the heat-resistant self-healing polyurethane elastic system according to claim 1, wherein The first solvent and the second solvent are independently selected from one or more of N,N-dimethylformamide, acetone and ethanol; the catalyst includes one or more of organotin and organolead.

5. A heat-resistant self-healing polyurethane elastic system prepared by the preparation method of the heat-resistant self-healing polyurethane elastic system according to claim 1.

6. The heat-resistant self-healing polyurethane elastic system according to claim 5, characterized in that, The low-temperature glass transition temperature of the heat-resistant self-healing polyurethane elastic system is less than -35 °C, and the high-temperature glass transition temperature is greater than 205 °C.

7. A polyurethane elastomer material, the preparation raw materials of which include the heat-resistant self-healing polyurethane elastic system according to claim 5.

8. Application of the heat-resistant self-healing polyurethane elastic system according to claim 5 in the preparation of polyurethane materials.

9. Application of the heat-resistant self-healing polyurethane elastic system according to claim 5 in the preparation of self-healing materials.

10. Application of the heat-resistant self-healing polyurethane elastic system according to claim 5 in the preparation of aerospace materials.

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