A high-strength, room-temperature self-healing lignin / polyurethane composite elastomer, its preparation method and application

Abstract

This invention belongs to the field of polyurethane elastomer technology and discloses a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer, its preparation method, and its applications. The preparation method includes the following steps: First, a long-chain diol, irregular isocyanate, hydrazine chain extender, and dioxime chain extender are progressively polymerized to obtain a polyurethane matrix with multiple dynamic bonds. Then, high-rigidity lignin and metal ions are introduced to prepare a lignin-reinforced polyurethane composite elastomer. The lignin / polyurethane composite elastomer prepared by this invention exhibits good compatibility, high strength, room-temperature self-healing, and repeatable heat processing characteristics, overcoming the problems of poor compatibility and the inability to simultaneously achieve high strength and low-temperature self-healing in general lignin-based polyurethane elastomers.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane elastomer technology, and specifically relates to a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer, its preparation method, and its application. Background Technology

[0002] Polyurethane is a block polymer composed of alternating flexible and rigid segments, exhibiting a highly tunable microphase separation structure. Due to its excellent wear resistance, high elasticity, processability, and biocompatibility, it is widely used in the automotive, military, and biomedical industries.

[0003] However, due to the complex application environments of polyurethane elastomers, they inevitably endure various effects such as external impacts, static loads, and friction during use, making them highly susceptible to damage such as microcracks, which severely impacts their reliability and service life. With increasing demands for material durability, self-healing polyurethanes have attracted widespread attention. Typically, self-healing effects rely on dynamic interactions, including dynamic covalent bonds (such as disulfide bonds, borate ester bonds, and oxime ester bonds) and dynamic non-covalent bonds (such as hydrogen bonds, metal coordination bonds, and host-guest interactions). By introducing dynamic reversible bonds into the polyurethane network, these dynamic bonds can spontaneously dissociate and recombine when the material is damaged, thereby repairing mechanical or chemical damage.

[0004] Furthermore, the preparation of most polyurethane elastomers relies primarily on non-renewable petroleum-based raw materials, and the extensive use of petrochemical resources has led to severe resource depletion and environmental problems. Therefore, the development of polyurethane elastomers urgently needs to enter a new era of high efficiency, green practices, safety, and multifunctionality. Lignin is the most abundant and only naturally occurring aromatic polymer in nature. Due to its high rigidity, renewability, and high hydroxyl content, it holds promise for replacing some petroleum-based raw materials in the synthesis of bio-based polyurethane elastomers. In addition, lignin possesses excellent antibacterial properties, UV resistance, and photothermal conversion capabilities, which are beneficial for developing multifunctional applications of lignin-based composite elastomers. Although lignin has enormous application potential and has been extensively studied in recent years, its poor dispersibility and tendency to agglomerate in polymers often result in low compatibility with polyurethane matrices. Moreover, because lignin has a rigid, multifunctional structure, the prepared lignin-based polyurethanes are usually cross-linked, which severely reduces the dynamic properties of the elastomer and limits its multifunctional applications.

[0005] Patent CN113754851A discloses a method for preparing a self-healing lignin-based polyurethane elastomer containing disulfide bonds. Although the prepared elastomer can achieve a self-healing efficiency of over 90% at 60°C, its tensile strength does not exceed 20 MPa, indicating poor mechanical properties that are difficult to meet practical application requirements.

[0006] Patent CN116903820A discloses a method for preparing self-healing lignin-based polyurethane by increasing the hydroxyl content of lignin through hydroxylation modification and using the modified lignin with DA chain extender. Although the modification improves the reactivity and compatibility of lignin with the matrix, and the prepared elastomer has a tensile strength of 29 MPa and a self-healing efficiency of 100%, its self-healing temperature is as high as 130℃, which is difficult to achieve in daily applications.

[0007] Patent CN115677972A discloses a method for preparing self-healing lignin-based polyurethane by constructing dynamic phenolic hydroxyl ester bonds and metal coordination bonds between lignin and a matrix. Although the lignin-based double crosslinked network enables the elastomer to have a tensile strength exceeding 30 MPa and achieves a self-healing rate of over 95% after 10 minutes of infrared light irradiation, the actual repair temperature under infrared light irradiation exceeds 100°C.

[0008] Patent CN113817130A discloses a method for preparing lignin-based polyurethane using a low-boiling-point, low-toxicity solvent to extract lignin and then using a solvent-free method. Although the process is relatively environmentally friendly and the prepared polyurethane has a tensile strength exceeding 40 MPa, its self-healing ability has not been investigated.

[0009] In summary, the reported lignin-based polyurethanes still have the following problems: First, because lignin is prone to self-aggregation and has poor dispersion in the matrix, the prepared lignin-based polyurethanes have low compatibility and poor mechanical properties. Second, polyurethanes prepared using lignin are usually cross-linked structures, which makes them unable to achieve self-healing or their self-healing temperature too high (usually exceeding 100℃), and even difficult to recycle and reuse. Summary of the Invention

[0010] In order to overcome the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0011] Another object of the present invention is to provide a lignin / polyurethane composite elastomer prepared by the above preparation method.

[0012] Another object of the present invention is to provide an application of the above-mentioned lignin / polyurethane composite elastomer.

[0013] The objective of this invention is achieved through the following technical solution:

[0014] A method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer includes the following steps:

[0015] (1) Dehydrate the long-chain diol under vacuum at 90-120℃ for 0.5-4h, then cool it to 60-90℃, dissolve it in an organic solvent, add a catalyst and isocyanate, stir the reaction for 1-4h to obtain a polyurethane prepolymer, then lower the reaction temperature to 25-60℃, add hydrazide chain extender and dioxime chain extender, and continue the reaction for 2-8h to obtain a polyurethane solution.

[0016] (2) Dissolve lignin and metal ions in an organic solvent, add them to the polyurethane solution obtained in step (1), stir at 300-1000 rpm for 0.5-3 h at room temperature, pour into a mold and dry at 60-120℃ to remove the solvent, and obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0017] The long-chain diol mentioned in step (1) has a relative molecular mass of 1000-4000, specifically one or more of polyethylene glycol, polybutene glycol, polycaprolactone glycol, polytetrahydrofuran ether glycol, and polycarbonate glycol.

[0018] The organic solvent is one or both of N,N-dimethylformamide and dimethyl sulfoxide;

[0019] The catalyst is dibutyltin dilaurate;

[0020] The isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, and tetramethylphenyl diisocyanate;

[0021] The chain extender of the acylhydrazine is one or more of the following: carbohydrazine, oxalic acid dihydrazine, succinic acid dihydrazine, adipic acid dihydrazine, and isophthalic acid dihydrazine;

[0022] The dioxime chain extender is one or more of butanedione dioxime, p-benzoquinone dioxime, 2,4-pentanedione dioxime, and 1,2-cyclohexanedione dioxime.

[0023] The lignin mentioned in step (2) is one or more of alkali lignin, enzymatically hydrolyzed lignin, and organic solvent lignin;

[0024] The metal ion is one or more of copper ions, iron ions, and zinc ions, specifically provided by one or more of the following metal salts: copper chloride, copper oxide, ferric chloride, zinc chloride, zinc oxide, zinc acetate, and zinc methacrylate.

[0025] The molar ratio of the long-chain diol, isocyanate, hydrazide chain extender, and dioxime chain extender in step (1) is 1:2-4:0.1-2:0.1-2; the amount of catalyst used is 0.1% of the total mass of the long-chain diol, isocyanate, hydrazide chain extender, and dioxime chain extender.

[0026] The relative molecular mass of the lignin in step (2) is between 1800 and 2100, the polydispersity index is between 1 and 1.2, and the hydroxyl content is 4-5 mmol / g; the amount of lignin used is 1-20% of the mass of the long-chain diol in step (1).

[0027] The molar ratio of the metal ions in step (2) to the dioxime chain extender in step (1) is 1:1-3.

[0028] A lignin / polyurethane composite elastomer prepared by the above preparation method has a tensile strength higher than 20 MPa, and can even reach more than 40 MPa. The self-healing temperature is room temperature (≈35℃), and the self-healing efficiency is higher than 80%, and can even exceed 90%.

[0029] The above-mentioned lignin / polyurethane composite elastomers are used in flexible drives and solar thermal power generation.

[0030] The principle of this invention is:

[0031] This invention utilizes irregular isocyanates reacting with hydrazide and oxime chain extenders to form polyurethane hard segments. The hydrazide chain extenders provide abundant hydrogen bonding interactions, while the oxime chain extenders can undergo dynamic reversible reactions and provide abundant nitrogen-atom ligands for metal coordination bonds. The irregular isocyanates prevent excessive aggregation of hard segments, ensuring their dynamic properties. Lignin is introduced as a green and environmentally friendly toughening agent to improve the mechanical properties of the polyurethane. Crucially, Zn is introduced... 2+ Constructing abundant metal coordination bonds between lignin and oxime esters not only effectively improves the compatibility between lignin and polyurethane but also provides an excellent energy dissipation mechanism for the composite material. This further enhances the mechanical properties of the elastomer while maintaining its excellent dynamic properties. Furthermore, the constraint of multiple interactions allows the prepared elastomer to maintain network structure stability at room temperature, preventing spontaneous fusion due to contact or overlap between different regions of the elastomer. However, after decoupling with a trace amount of ethanol solvent, it can achieve highly efficient self-healing at room temperature. This rational combination strategy of a flexible matrix and rigid lignin enables the prepared lignin / polyurethane composite elastomer to possess both high strength and room-temperature self-healing characteristics.

[0032] The present invention has the following advantages and effects compared with the prior art:

[0033] (1) The present invention uses dynamic reversible hydrazide and oxime chain extenders, which not only provide excellent dynamic properties for elastomers, but also provide abundant ligands for metal coordination bonds.

[0034] (2) This invention introduces Zn 2+Abundant metal coordination bonds were constructed between lignin and oxime ester, effectively improving the compatibility of the two phases.

[0035] (3) The lignin / polyurethane composite elastomer prepared by the present invention has stable multiple interactions, which enables the elastomer to precisely switch between stable and excellent mechanical properties and high-efficiency self-healing at room temperature to meet the needs of practical applications.

[0036] (4) The lignin / polyurethane composite elastomer prepared by the present invention reduces the demand and dependence of polyurethane on petrochemical resources and realizes the high-value utilization of lignin. Attached Figure Description

[0037] Figure 1 This describes the preparation route for lignin / polyurethane composite elastomers.

[0038] Figure 2 The infrared spectra of Examples 1-4 and Comparative Example 1 are shown.

[0039] Figure 3 The images are SEM images of Example 2 and Comparative Example 2.

[0040] Figure 4 These are SEM images before and after self-healing in Example 2. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but should not be construed as limiting the present invention.

[0042] Tensile test conditions: The heat-dried elastomer was cut into standard dumbbell-shaped samples with a length of 50 mm, a width of 4 mm, a length of 17 mm, and a thickness of 1 mm. The tensile interval was 30 mm. The test was conducted using an electronic universal testing machine (* / Inspekt Table Blue5KN, Hegewald & Peschke, Germany). The test temperature was room temperature, and the tensile rate was 50 mm / min.

[0043] Self-healing test conditions: The sample was completely cut in half, the cut was then closed, 50 μL of ethanol solution was added, and the sample was placed at 35°C for 24 hours. The self-healing efficiency of the repaired sample was evaluated by tensile testing.

[0044] Structural characterization: Fourier transform infrared spectroscopy (Thermo-Fisher, USA) was used in attenuated total reflectance (ATR) mode, with a scanning range of 400-4000 cm⁻¹. -1 The number of scans was 32.

[0045] Microscopic morphology analysis: Characterization was performed using a field emission scanning electron microscope (SEM) (SU8220, Hitachi, Japan).

[0046] The synthetic route of the lignin-based polyurethane elastomer in the following examples is as follows: Figure 1 As shown.

[0047] Example 1

[0048] 1. Weigh 5 parts by mass of polytetrahydrofuran ether diol (Mn = 2000) and vacuum dry it at 110℃ for 2 hours to remove moisture; then cool it to 80℃, add 10 parts by mass of N,N-dimethylformamide, 1.7 parts by mass of isophorone diisocyanate, and 0.01 parts by mass of catalyst, and stir the reaction at 300 rpm for 3 hours to obtain a polyurethane prepolymer solution; then lower the temperature to 50℃, add 0.4 parts by mass of adipic acid dihydrazide and 0.3 parts by mass of dimethylglyoxime, and continue the reaction for 3 hours to obtain a polyurethane solution.

[0049] 2. Dissolve 0.125 parts by weight of alkali lignin and 0.2 parts by weight of zinc chloride in 5 parts by weight of N,N-dimethylformamide, add to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 h at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 h to remove the solvent, to obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0050] Example 2

[0051] 1. Same as Example 1.

[0052] 2. Dissolve 0.25 parts by weight of alkali lignin and 0.2 parts by weight of zinc chloride in 5 parts by weight of N,N-dimethylformamide, add to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 hour at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 hours to remove the solvent, to obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0053] Example 3

[0054] 1. Same as Example 1.

[0055] 2. Dissolve 0.375 parts by weight of alkali lignin and 0.2 parts by weight of zinc chloride in 5 parts by weight of N,N-dimethylformamide, add to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 hour at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 hours to remove the solvent, thereby obtaining a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0056] Example 4

[0057] 1. Same as Example 1.

[0058] 2. Dissolve 0.5 parts by weight of alkali lignin and 0.2 parts by weight of zinc chloride in 5 parts by weight of N,N-dimethylformamide, add to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 h at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 h to remove the solvent, to obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0059] Example 5

[0060] 1. Same as Example 1.

[0061] 2. Dissolve 0.25 parts by weight of alkali lignin and 0.1 parts by weight of zinc chloride in 5 parts by weight of N,N-dimethylformamide, add to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 hour at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 hours to remove the solvent, to obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0062] Example 6

[0063] 1. Same as Example 1.

[0064] 2. Dissolve 0.25 parts by weight of alkali lignin and 0.3 parts by weight of zinc chloride in 5 parts by weight of N,N-dimethylformamide, add to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 h at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 h to remove the solvent, to obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

[0065] Example 7

[0066] 1. Weigh 5 parts by mass of polytetrahydrofuran ether diol (Mn = 2000) and vacuum dry it at 110℃ for 2 hours to remove moisture; then cool it to 80℃, add 10 parts by mass of N,N-dimethylformamide, 1.7 parts by mass of isophorone diisocyanate, and 0.01 parts by mass of catalyst, and stir the reaction at 300 rpm for 3 hours to obtain a polyurethane prepolymer solution; then lower the temperature to 50℃, add 0.6 parts by mass of adipic acid dihydrazide and 0.15 parts by mass of dimethylglyoxime, and continue the reaction for 3 hours to obtain a polyurethane solution.

[0067] 2. Same as Example 2.

[0068] Example 8

[0069] 1. Weigh 5 parts by mass of polytetrahydrofuran ether diol (Mn = 2000) and vacuum dry it at 110℃ for 2 hours to remove moisture; then cool it to 80℃, add 10 parts by mass of N,N-dimethylformamide, 1.7 parts by mass of isophorone diisocyanate, and 0.01 parts by mass of catalyst, and stir the reaction at 300 rpm for 3 hours to obtain a polyurethane prepolymer solution; then lower the temperature to 50℃, add 0.2 parts by mass of adipic acid dihydrazide and 0.45 parts by mass of dimethylglyoxime, and continue the reaction for 3 hours to obtain a polyurethane solution.

[0070] 2. Same as Example 2.

[0071] Comparative Example 1

[0072] 1. Weigh 5 parts by mass of polytetrahydrofuran ether diol (Mn = 2000) and vacuum dry at 110℃ for 2 hours to remove moisture; then cool to 80℃, add 10 parts by mass of N,N-dimethylformamide, 1.7 parts by mass of isophorone diisocyanate, and 0.01 parts by mass of catalyst, and stir at 300 rpm for 3 hours to obtain a polyurethane prepolymer solution; then lower the temperature to 50℃, add 0.4 parts by mass of adipic acid dihydrazide and 0.3 parts by mass of dimethylglyoxime, and continue the reaction for 3 hours to obtain a polyurethane solution. Then pour the solution into a polytetrafluoroethylene mold and dry at 80℃ for 24 hours to remove the solvent, obtaining a composite elastomer.

[0073] Comparative Example 2

[0074] 1. Same as Example 1.

[0075] 2. Dissolve 0.25 parts by weight of alkali lignin in 5 parts by weight of N,N-dimethylformamide, add it to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 hour at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 hours to remove the solvent, thereby obtaining the composite elastomer.

[0076] Comparative Example 3

[0077] 1. Same as Example 1.

[0078] 2. Dissolve 0.2 parts by mass of zinc chloride in 5 parts by mass of N,N-dimethylformamide, add it to the polyurethane solution obtained in step 1, stir at 600 rpm for 1 hour at room temperature, then pour the solution into a polytetrafluoroethylene mold and dry at 80°C for 24 hours to remove the solvent, thus obtaining the composite elastomer.

[0079] Comparative Example 4

[0080] 1. Weigh 5 parts by mass of polytetrahydrofuran ether diol (Mn = 2000) and vacuum dry it at 110℃ for 2 hours to remove moisture; then cool it to 80℃, add 10 parts by mass of N,N-dimethylformamide, 1.7 parts by mass of isophorone diisocyanate, and 0.01 parts by mass of catalyst, and stir the reaction at 300 rpm for 3 hours to obtain a polyurethane prepolymer solution; then lower the temperature to 50℃, add 0.8 parts by mass of adipic acid dihydrazide, and continue the reaction for 3 hours to obtain a polyurethane solution.

[0081] 2. Same as in Example 2, the final composite elastomer is obtained.

[0082] Comparative Example 5

[0083] 1. Weigh 5 parts by mass of polytetrahydrofuran ether diol (Mn = 2000) and vacuum dry it at 110℃ for 2 hours to remove moisture; then cool it to 80℃, add 10 parts by mass of N,N-dimethylformamide, 1.7 parts by mass of isophorone diisocyanate, and 0.01 parts by mass of catalyst, and stir the mixture at 300 rpm for 3 hours to obtain a polyurethane prepolymer solution; then lower the temperature to 50℃, add 0.6 parts by mass of dimethylglyoxime, and continue the reaction for 3 hours to obtain a polyurethane solution.

[0084] 2. Same as in Example 2, the final composite elastomer is obtained.

[0085] The elastomers obtained in Examples 1-8 and Comparative Examples 1-5 were tested for various mechanical properties, including tensile strength, elongation at break, and self-healing rate. The results are shown in Table 1.

[0086] Table 1 Mechanical properties of Examples 1-8 and Comparative Examples 1-5

[0087]

[0088] As shown in Table 1, the composite elastomer prepared with lignin exhibits significantly improved mechanical properties compared to the elastomer without lignin, while maintaining excellent self-healing efficiency. The introduction of Zn... 2+ Lignin / polyurethane composite elastomers compared to those without Zn 2+ The mechanical properties of the elastomer were also effectively improved, indicating that the construction of metal coordination bonds improved the compatibility between lignin and polyurethane matrix, allowing lignin to fully exert its toughening effect, and also providing an excellent energy dissipation mechanism for the composite system.

[0089] Figure 2 Infrared spectra of the elastomers prepared in Comparative Example 1 and Examples 1-4. All samples were analyzed at 3300 cm⁻¹. -1 and 1650cm -1There are obvious absorption peaks at 985 cm⁻¹, corresponding to the stretching vibration absorption peaks of NH₃ and C=O, respectively. These two peaks are typical characteristic peaks of polyurethane structures. Meanwhile, at 985 cm⁻¹... -1 A vibrational absorption peak representing the NO bond appeared at 2270 cm⁻¹. Furthermore, a peak was observed at 2270 cm⁻¹. -1 No absorption peaks representing isocyanate were observed on either side, indicating that the isocyanate had been completely consumed, and the polyurethane elastomer was successfully synthesized.

[0090] Figure 3 The images show SEM images of Example 2 and Comparative Example 2. It can be seen that the lignin particles in Example 2 are uniformly distributed in the polyurethane matrix, and the particle sizes are relatively similar. In contrast, the lignin particles in Comparative Example 2 are severely agglomerated, and the particle sizes vary considerably. This indicates that Zn... 2+ The introduction of [the substance] enhances the compatibility and dispersibility of lignin with the polyurethane matrix.

[0091] Figure 4 The images show SEM images of the sample before and after self-healing in Example 2. It can be seen that after 24 hours of repair, the cuts on the sample disappeared, and the surface morphology returned to a smooth state, indicating that the sample had essentially completed self-healing.

[0092] The above embodiments are suitable implementations of the present invention. The implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer, characterized in that... Follow these steps: (1) Dehydrate the long-chain diol under vacuum at 90-120℃ for 0.5-4h, then cool it to 60-90℃, dissolve it in an organic solvent, add a catalyst and isocyanate, stir the reaction for 1-4h to obtain a polyurethane prepolymer, then lower the reaction temperature to 25-60℃, add hydrazide chain extender and dioxime chain extender, continue the reaction for 2-8h to obtain a polyurethane solution; The long-chain diols have a relative molecular mass of 1000-4000, and are specifically one or more of polyethylene glycol, polybutene glycol, polycaprolactone glycol, polytetrahydrofuran ether glycol, and polycarbonate glycol. The isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, and tetramethylphenyl diisocyanate; The chain extender of the acylhydrazine is one or more of the following: carbohydrazine, oxalic acid dihydrazine, succinic acid dihydrazine, adipic acid dihydrazine, and isophthalic acid dihydrazine; The dioxime chain extender is one or more selected from butanedione dioxime, p-benzoquinone dioxime, 2,4-pentanedione dioxime, and 1,2-cyclohexanedione dioxime; (2) Dissolve lignin and metal ions in an organic solvent, add them to the polyurethane solution obtained in step (1), stir at 300-1000 rpm for 0.5-3 h at room temperature, pour into a mold and dry at 60-120℃ to remove the solvent, and obtain a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer.

2. The method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer according to claim 1, characterized in that: The organic solvent in step (1) is one or both of N,N-dimethylformamide and dimethyl sulfoxide; the catalyst is dibutyltin dilaurate.

3. The method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer according to claim 1, characterized in that: The lignin mentioned in step (2) is one or more of alkali lignin, enzymatically hydrolyzed lignin, and organic solvent lignin; The metal ion is one or more of copper ions, iron ions, and zinc ions, specifically provided by one or more of the following metal salts: copper chloride, copper oxide, ferric chloride, zinc chloride, zinc oxide, zinc acetate, and zinc methacrylate.

4. The method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer according to claim 1, characterized in that: The molar ratio of the long-chain diol, isocyanate, hydrazide chain extender, and dioxime chain extender in step (1) is 1:2-4:0.1-2:0.1-2; the amount of catalyst used is 0.1% of the total mass of the long-chain diol, isocyanate, hydrazide chain extender, and dioxime chain extender.

5. The method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer according to claim 1, characterized in that: The relative molecular mass of the lignin in step (2) is between 1800 and 2100, the polydispersity index is between 1 and 1.2, and the hydroxyl content is 4-5 mmol / g; the amount of lignin used is 1-20% of the mass of the long-chain diol in step (1).

6. The method for preparing a high-strength, room-temperature self-healing lignin / polyurethane composite elastomer according to claim 1, characterized in that: The molar ratio of the metal ions in step (2) to the dioxime chain extender in step (1) is 1:1-3.

7. A lignin / polyurethane composite elastomer prepared by the preparation method according to any one of claims 1-6, characterized in that: The tensile strength of the lignin / polyurethane composite elastomers is all higher than 20 MPa, the self-healing temperature is all room temperature, and the self-healing efficiency is all higher than 80%.

8. The lignin / polyurethane composite elastomer according to claim 7, characterized in that: The tensile strength of the lignin / polyurethane composite elastomer reaches over 40 MPa, and the self-healing efficiency reaches over 90%.

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