Polyurethane elastomer as well as preparation method and application thereof

Abstract

The invention relates to a polyurethane elastomer as well as a preparation method and application thereof. The polyurethane elastomer is prepared from the following raw materials: a hydroxyl-terminated polymer, diisocyanate, a first chain extender and a second chain extender, the first chain extender comprises a compound with a specific structure and eight hydrogen bonds; the second chain extender comprises any one or a combination of at least two of a polyol chain extender, a diamine chain extender or an alcohol amine chain extender. The polyurethane elastomer provided by the invention is high in hydrogen bond density and strong in interaction between macromolecular chains, and the reversible hydrogen bond interaction can effectively dissipate energy, so that the polyurethane elastomer has excellent mechanical strength, stretchability and self-repairing performance at the same time, and can adapt to application requirements in multiple fields.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a polyurethane elastomer and a preparation method and application thereof. Background Art

[0002] With the continuous development of modern science and technology, the global demand for polymer materials with excellent performance has increased year by year. As an emerging polymer material, polyurethane is widely used in many fields of national life because of its excellent properties such as wear resistance, corrosion resistance and high elasticity. Polyurethane (PU) is a general term for a class of polymer compounds containing carbamate (─NH─COO─) units in the main chain. It is a multi-block polymer formed by the gradual polymerization of polyols, chain extenders and polyisocyanates. Polyols constitute the soft segment, and chain extenders and polyisocyanates constitute the hard segment. The molecular structure and properties of polyurethane can be effectively controlled by adjusting the components and proportions in the soft and hard segments. Among them, the hard segment has a strong polarity and is easy to form an aggregate phase; the soft segment is an amorphous phase. The thermodynamic incompatibility of the hard segment and the soft segment can form a microphase separation structure. The microphase separation structure enables polyurethane to have a better energy dissipation mechanism than other polymer materials. However, polyurethane will inevitably be subjected to various loads during use, and it is very easy to produce microcrack damage in weak parts, which poses a serious threat to the safety and service life of the material. Inspired by the wound healing mechanism of organisms in nature, self-healing ability is introduced into polymers. The material is designed to have self-healing properties to repair microcrack damage, which can effectively extend the service life of the material, reduce maintenance costs and reduce resource waste.

[0003] At present, the self-healing polyurethane elastomers in the existing technology generally have problems with balancing self-healing properties and mechanical properties and have a yellowing appearance, which limits their application in electronic instruments, surface protection, automotive coatings, flexible wearable devices, and smart response materials.

[0004] CN106589287A discloses a self-healing polyurethane based on multiple hydrogen bond primitives and a preparation method thereof. A 2-urea-4[1H]-pyrimidinedione (UPy) system is used to construct a quadruple hydrogen bond, and a self-healing polyurethane is prepared. The material introduces cyclodextrin into the main chain to improve mechanical properties, and the synergistic reversible quadruple hydrogen bond and dynamic host-guest interaction give the material self-healing properties. The repair efficiency after repairing at 50°C for 6 hours is 78%. CN113831493A provides a self-healing polyurethane elastomer containing six-fold intermolecular hydrogen bonds and a preparation method thereof. A self-healing polyurethane elastomer is developed using 2,6-diaminopyridine or a derivative of 2,6-diaminopyridine as a chain extender. The elongation at break of the elastomer is high, but the mechanical strength is poor.

[0005] Therefore, there is an urgent need in the art to develop a polyurethane material having excellent mechanical strength, stretchability and self-healing effect. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a polyurethane elastomer and a preparation method and application thereof. By introducing a chain extender having an octet hydrogen bond unit and coordinating it with other components, the obtained polyurethane elastomer has high tensile strength, high elongation at break and self-repairing performance. The required conditions are mild, the operation is simple, the repair speed is fast and the repair effect is good.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a polyurethane elastomer, wherein the raw materials for preparing the polyurethane elastomer include the following components: a terminal hydroxyl polymer, a diisocyanate, a first chain extender and a second chain extender;

[0009] The first chain extender includes a compound having a structure as shown in Formula I:

[0010]

[0011] The second chain extender includes any one of a polyol chain extender, a diamine chain extender or an alcohol amine chain extender, or a combination of at least two of them.

[0012] The polyurethane elastomer provided by the present invention is prepared by compounding a chain extender with a specific structure with other components, wherein the chain extender having an octet hydrogen bond unit has a higher hydrogen bond density, provides a stronger interaction between polymer chains, and promotes the spontaneous formation of a nano-confined phase as a physical cross-linking point in the polyurethane, thereby giving the material excellent mechanical strength; a large number of reversible octet hydrogen bonds can effectively dissipate energy during the stress process of the polyurethane polymer, thereby giving the material super tensile strength and toughness; at the same time, the reversibility of the octet hydrogen bond gives the polyurethane self-healing performance, so that the prepared polyurethane elastomer has excellent mechanical strength, tensile strength and self-healing performance, and can meet the application needs of multiple fields.

[0013] Preferably, the molar ratio of the hydroxyl group in the terminal hydroxyl polymer to the isocyanate group in the diisocyanate is 1:(1-5), wherein the specific value in (1-5) can be, for example, 1.5, 2, 2.5, 3, 3.5, 4 or 4.5, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, and it is further preferably 1:(1.8-3).

[0014] Preferably, the molar ratio of the first chain extender to the second chain extender is 1:(1-10), wherein the specific value of (1-10) can be, for example, 2, 3, 4, 5, 6, 7, 8 or 9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, and is further preferably 1:(4-7).

[0015] As a preferred technical solution of the present invention, when the molar ratio of the first chain extender to the second chain extender is 1:(4-7), the obtained polyurethane elastomer has more excellent tensile properties and self-healing properties. When the proportion of the first chain extender is low, the hydrogen bond density in the polyurethane elastomer is low and the self-healing property is insufficient; when the proportion of the first chain extender is high, the mechanical strength of the obtained polyurethane elastomer is significantly reduced.

[0016] Preferably, the total molar amount of the first chain extender and the second chain extender is the difference between the molar amount of the diisocyanate and the molar amount of the terminal hydroxyl polymer.

[0017] Preferably, the hydroxyl-terminated polymer includes any one of polypropylene glycol, hydrogenated hydroxyl-terminated polybutadiene, hydroxyl-terminated polybutadiene acrylonitrile or polytetrahydrofuran, or a combination of at least two thereof.

[0018] Preferably, the weight average molecular weight of the hydroxyl-terminated polymer is 500-5000 g / mol, for example, 800 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 3000 g / mol or 4000 g / mol.

[0019] Preferably, the diisocyanate includes any one of isophorone diisocyanate, 2,6-toluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate or 1,3-diisophenyl cyanate, or a combination of at least two thereof.

[0020] Preferably, the second chain extender is a bifunctional chain extender.

[0021] Preferably, the polyol chain extender comprises diol.

[0022] Preferably, the diol includes any one of 1,4-butanediol, ethylene glycol, diethylene glycol or 1,4-cyclohexanediol, or a combination of at least two thereof.

[0023] Preferably, the diamine chain extender includes any one of diethyltoluenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane or 3,5-diamino-p-chlorobenzoic acid isobutyl ester or a combination of at least two thereof.

[0024] Preferably, the alcoholamine chain extender includes any one of ethanolamine, diethanolamine or N-methyldiethanolamine, or a combination of at least two thereof.

[0025] Preferably, the prepared raw material further comprises a catalyst.

[0026] Preferably, the catalyst comprises an organotin catalyst.

[0027] Preferably, the organotin catalyst includes any one of dibutyltin dilaurate, di-n-octyltin dilaurate or stannous octoate, or a combination of at least two thereof.

[0028] Preferably, based on 100 parts by total weight of the terminal hydroxyl polymer, the diisocyanate, the first chain extender and the second chain extender, the weight of the catalyst is 0.05-0.3 parts, for example, 0.08 parts, 0.1 parts, 0.15 parts, 0.2 parts or 0.25 parts, etc.;

[0029] Preferably, the preparation raw material also includes a solvent.

[0030] Preferably, the solvent includes any one of N,N-dimethylformamide, N,N-dimethylacetamide or tetrahydrofuran, or a combination of at least two thereof.

[0031] The amount of the solvent used in the present invention is selected by those skilled in the art based on experience and process requirements, so long as the raw materials can be dissolved.

[0032] In a second aspect, the present invention provides a method for preparing the polyurethane elastomer as described in the first aspect, the preparation method comprising the following steps:

[0033] (1) mixing a hydroxyl-terminated polymer, a diisocyanate, an optional catalyst and an optional solvent to react to obtain a prepolymer;

[0034] (2) The prepolymer obtained in step (1) is sequentially mixed with a first chain extender and a second chain extender to react, and a polyurethane elastomer is obtained after removing the solvent.

[0035] In the polyurethane elastomer preparation method provided in the present invention, the first chain extender and the second chain extender react with the prepolymer in sequence, which can avoid the adverse effects caused by the steric hindrance effect and accurately control the polymer properties; if the two are added at the same time or the order of addition is changed, the steric hindrance effect between the molecules of the first chain extender will seriously affect the final mechanical strength and self-healing properties of the polymer.

[0036] Preferably, in step (1), the reaction temperature is 40-100°C, for example, 50°C, 60°C, 70°C, 80°C or 90°C, as well as specific values ​​between the above-mentioned points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0037] Preferably, in step (1), the reaction time is 2-24 h, for example, 4 h, 6 h, 8 h, 10 h, 12 h, 16 h or 20 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0038] Preferably, in step (1), the reaction is carried out in the presence of a protective gas.

[0039] Preferably, the protective gas includes any one of nitrogen, argon or helium, or a combination of at least two of them.

[0040] Preferably, the reaction temperature with the first chain extender in step (2) is 40-100°C, for example, 50°C, 60°C, 70°C, 80°C or 90°C, as well as specific values ​​between the above-mentioned points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0041] Preferably, the reaction time with the first chain extender in step (2) is 2-24 h, for example, 4 h, 6 h, 8 h, 10 h, 12 h, 16 h or 20 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0042] Preferably, the reaction temperature with the second chain extender in step (2) is 40-100°C, for example, 50°C, 60°C, 70°C, 80°C or 90°C, as well as specific values ​​between the above-mentioned points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0043] Preferably, the reaction time with the second chain extender in step (2) is 2-24 h, for example, 4 h, 6 h, 8 h, 10 h, 12 h, 16 h or 20 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0044] Preferably, the preparation method comprises the following steps:

[0045] (1) mixing a hydroxyl-terminated polymer, a diisocyanate, a catalyst and a solvent, and reacting the mixture at 40-100° C. for 2-24 hours to obtain a prepolymer;

[0046] (2) The prepolymer obtained in step (1) is mixed with a first chain extender and reacted at 40-100° C. for 2-24 hours, and then a second chain extender is added and mixed at 40-100° C. for 2-24 hours, and the solvent is removed to obtain a polyurethane elastomer.

[0047] In a third aspect, the present invention provides an application of the polyurethane elastomer as described in the first aspect in electronic instruments, protective coatings, flexible wearable devices or smart response materials.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] The polyurethane elastomer provided by the present invention introduces an octet hydrogen bond unit into the polymer, thereby increasing the hydrogen bond density and enhancing the interaction between polymer chains, thereby obtaining a polyurethane elastomer with excellent mechanical properties, stretchable properties and self-repairing properties, wherein the tensile strength is ≥4.8MPa, the elongation at break is ≥1300%, and the self-repairing efficiency is ≥32%. DETAILED DESCRIPTION

[0050] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0051] In the following specific implementation of the present invention, the materials involved are as follows:

[0052] Hydrogenated hydroxy-terminated polybutadiene, Krasol, HLBH-P3000

[0053] Polypropylene glycol, MacLean, P815571;

[0054] Hydroxyl-terminated polybutadiene acrylonitrile, Tangyi, TL910;

[0055] Polytetrahydrofuran, MacLean, P816778.

[0056] Example 1

[0057] A polyurethane elastomer is prepared by the following method:

[0058] At 80° C., 25 mmol of hydrogenated hydroxy-terminated polybutadiene, 50 mmol of dicyclohexylmethane diisocyanate and dibutyltin dilaurate are added to 80 mL of N,N-dimethylformamide to make the mass concentration of dibutyltin dilaurate 0.1%, and the mixture is reacted for 4 hours under N2 atmosphere; 5 mmol of the first chain extender (compound of formula I structure) is added to the reaction and the reaction is continued for 4 hours at 80° C., and then 20 mmol of the second chain extender 1,4-butanediol is added and the reaction is continued for 4 hours at 80° C.; the solvent is removed to obtain the polyurethane elastomer.

[0059] Example 2

[0060] A polyurethane elastomer is prepared by the following method:

[0061] At 100° C., 25 mmol of terminal hydroxyl polybutadiene acrylonitrile, 45 mmol of 2,6-toluene diisocyanate and stannous octoate are added to 80 mL of N,N-dimethylacetamide to make the mass concentration of stannous octoate 0.1%, and react for 24 hours under N2; 4 mmol of the first chain extender (compound of formula I structure) is added to the reaction and the reaction is continued at 100° C. for 24 hours, and then 16 mmol of the second chain extender diethanolamine is added and the reaction is continued at 100° C. for 24 hours; the solvent is removed to obtain the polyurethane elastomer.

[0062] Example 3

[0063] A polyurethane elastomer is prepared by the following method:

[0064] At 80° C., 25 mmol of polytetrahydrofuran, 50 mmol of 1,3-diisobenzocyanate and dibutyltin dilaurate are added to 80 mL of N,N-dimethylformamide to make the mass concentration of dibutyltin dilaurate 0.1%, and react for 4 hours under N2; 5 mmol of the first chain extender (compound of formula I structure) is added to the reaction and the reaction is continued for 4 hours at 80° C., and then 20 mmol of the second chain extender 1,4-butanediol is added and the reaction is continued for 4 hours at 80° C.; the solvent is removed to obtain the polyurethane elastomer.

[0065] Example 4

[0066] A polyurethane elastomer is prepared by the following method:

[0067] At 80° C., 25 mmol of hydrogenated hydroxy-terminated polybutadiene, 50 mmol of dicyclohexylmethane diisocyanate and dibutyltin dilaurate are added to 80 mL of N,N-dimethylformamide to make the mass concentration of dibutyltin dilaurate 0.1%, and the mixture is reacted for 4 hours under N2 atmosphere; 3.125 mmol of the first chain extender (compound of formula I structure) is added to the reaction and the reaction is continued for 4 hours at 80° C., and then 21.875 mmol of the second chain extender 1,4-butanediol is added and the reaction is continued for 4 hours at 80° C.; the solvent is removed to obtain the polyurethane elastomer.

[0068] Example 5

[0069] A polyurethane elastomer is prepared by the following method:

[0070] At 80° C., 25 mmol of hydrogenated hydroxy-terminated polybutadiene, 50 mmol of dicyclohexylmethane diisocyanate and dibutyltin dilaurate are added to 80 mL of N,N-dimethylformamide to make the mass concentration of dibutyltin dilaurate 0.1%, and the mixture is reacted for 4 hours under N2 atmosphere; 8.33 mmol of the first chain extender (compound of formula I structure) is added to the reaction and the reaction is continued for 4 hours at 80° C., and then 16.67 mmol of the second chain extender 1,4-butanediol is added and the reaction is continued for 4 hours at 80° C.; the solvent is removed to obtain the polyurethane elastomer.

[0071] Example 6

[0072] A polyurethane elastomer is prepared by the following method:

[0073] At 40° C., 25 mmol of polypropylene glycol, 45 mmol of isophorone diisocyanate and di-n-octyltin dilaurate are added to 80 mL of tetrahydrofuran to make the mass concentration of dibutyltin dilaurate 0.1%, and the mixture is reacted for 2 hours under a N2 atmosphere; 2 mmol of a first chain extender (compound of formula I structure) is added to the reaction and the reaction is continued for 2 hours at 40° C., and then 18 mmol of a second chain extender, diethyltoluenediamine, is added and the reaction is continued for 2 hours at 40° C.; the solvent is removed to obtain the polyurethane elastomer.

[0074] Comparative Example 1

[0075] A polyurethane elastomer is prepared by the following method:

[0076] At 80° C., 25 mmol of hydrogenated hydroxy-terminated polybutadiene, 50 mmol of dicyclohexylmethane diisocyanate and dibutyltin dilaurate are added to 80 mL of N,N-dimethylformamide to make the mass concentration of dibutyltin dilaurate 0.1%, and the mixture is reacted for 4 hours under a N2 atmosphere; 25 mmol of a first chain extender (compound of formula I) is added to the reaction and the reaction is continued for 4 hours at 80° C.; the solvent is removed to obtain the polyurethane elastomer.

[0077] Comparative Example 2

[0078] A polyurethane elastomer is prepared by the following method:

[0079] At 80° C., 25 mmol of hydrogenated hydroxy-terminated polybutadiene, 50 mmol of dicyclohexylmethane diisocyanate and dibutyltin dilaurate are added to 80 mL of N,N-dimethylformamide to make the mass concentration of dibutyltin dilaurate 0.1%, and react for 4 hours under N2 atmosphere; 25 mmol of a second chain extender 1,4-butanediol is added and the reaction is continued at 80° C. for 4 hours; and the solvent is removed to obtain the polyurethane elastomer.

[0080] Performance Testing

[0081] The polyurethane elastomers described in Examples 1-6 and Comparative Examples 1-2 were tested as follows:

[0082] (1) Tensile strength and elongation at break: Tested in accordance with GB / T 1447-2005 Test method for tensile properties of fiber reinforced plastics.

[0083] (2) Self-repair efficiency: The polyurethane material was cut into two sections, and the sections were repaired at 100° C. for 36 hours after being reconnected. The tensile strength was tested according to GB / T 1447-2005 Test method for tensile properties of fiber reinforced plastics. The ratio of the tensile strength after repair to the original tensile strength was used to characterize the self-repair efficiency.

[0084] The test results are summarized in Table 1.

[0085] Table 1

[0086]

[0087] It can be seen from the test results that the polyurethane elastomer provided by the present invention is compounded with a chain extender having an octet hydrogen bond unit and other components to obtain a polyurethane elastomer with excellent mechanical properties, stretchable properties and self-healing properties, with a tensile strength of ≥4.8MPa, an elongation at break ≥1300%, and a self-healing efficiency ≥32%.

[0088] By comparing Example 1 with Examples 5 and 6, it can be seen that the present invention obtains a polyurethane elastomer with higher tensile strength by further limiting the ratio of the first chain extender to the second chain extender; when the ratio of the first chain extender is large, there are too many hydrogen bonds, resulting in a significant decrease in the tensile strength of the material, and it is easy to break during use; when the ratio of the second chain extender is too large, the mechanical strength and self-healing effect of the material are significantly deteriorated.

[0089] By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the present invention adopts a combination of the first chain extender and the second chain extender, so that the prepared polyurethane elastomer has excellent tensile strength, elongation at break and self-healing performance, which can meet the application requirements in multiple fields.

[0090] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyurethane elastomer, characterized in that: The raw materials for preparing the polyurethane elastomer include the following components: a terminal hydroxyl polymer, a diisocyanate, a first chain extender and a second chain extender; The first chain extender includes a compound having a structure as shown in Formula I: The second chain extender includes any one of a polyol chain extender, a diamine chain extender or an alcohol amine chain extender, or a combination of at least two of them.

2. The polyurethane elastomer according to claim 1, characterized in that The molar ratio of the hydroxyl group in the hydroxyl-terminated polymer to the isocyanate group in the diisocyanate is 1:(1-5), preferably 1:(1.8-3); Preferably, the molar ratio of the first chain extender to the second chain extender is 1:(1-10), more preferably 1:(4-7); Preferably, the total molar amount of the first chain extender and the second chain extender is the difference between the molar amount of the diisocyanate and the molar amount of the terminal hydroxyl polymer.

3. The polyurethane elastomer according to claim 1 or 2, characterized in that: The hydroxyl-terminated polymer includes any one of polypropylene glycol, hydrogenated hydroxyl-terminated polybutadiene, hydroxyl-terminated polybutadiene acrylonitrile or polytetrahydrofuran, or a combination of at least two thereof; Preferably, the weight average molecular weight of the hydroxyl-terminated polymer is 500-5000 g / mol; Preferably, the diisocyanate includes any one of isophorone diisocyanate, 2,6-toluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate or 1,3-diisophenyl cyanate, or a combination of at least two thereof.

4. The polyurethane elastomer according to any one of claims 1 to 3, characterized in that: The polyol chain extender includes diol; Preferably, the diol includes any one or a combination of at least two of 1,4-butanediol, ethylene glycol, diethylene glycol or 1,4-cyclohexanediol; Preferably, the diamine chain extender includes any one of diethyltoluenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane or 3,5-diamino-p-chlorobenzoic acid isobutyl ester or a combination of at least two thereof; Preferably, the alcoholamine chain extender includes any one of ethanolamine, diethanolamine or N-methyldiethanolamine, or a combination of at least two thereof.

5. The polyurethane elastomer according to any one of claims 1 to 4, characterized in that: The preparation raw materials also include a catalyst; Preferably, the catalyst comprises an organotin catalyst; Preferably, the organotin catalyst comprises any one of dibutyltin dilaurate, di-n-octyltin dilaurate or stannous octoate, or a combination of at least two thereof; Preferably, based on 100 parts by total weight of the terminal hydroxyl polymer, the diisocyanate, the first chain extender and the second chain extender, the weight of the catalyst is 0.05-0.3 parts.

6. The polyurethane elastomer according to any one of claims 1 to 5, characterized in that: The preparation raw materials also include a solvent; Preferably, the solvent includes any one of N,N-dimethylformamide, N,N-dimethylacetamide or tetrahydrofuran, or a combination of at least two thereof.

7. A method for preparing a polyurethane elastomer according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: (1) mixing a hydroxyl-terminated polymer, a diisocyanate, an optional catalyst and an optional solvent to react to obtain a prepolymer; (2) The prepolymer obtained in step (1) is sequentially mixed with a first chain extender and a second chain extender to react, and a polyurethane elastomer is obtained after removing the solvent.

8. The preparation method according to claim 7, characterized in that: In step (1), the reaction temperature is 40-100°C; Preferably, in step (1), the reaction time is 2-24h; Preferably, in step (1), the reaction is carried out in the presence of a protective gas; Preferably, the protective gas comprises any one of nitrogen, argon or helium, or a combination of at least two thereof; Preferably, the reaction temperature with the first chain extender in step (2) is 40-100°C; Preferably, the reaction time with the first chain extender in step (2) is 2-24h; Preferably, the reaction temperature with the second chain extender in step (2) is 40-100°C; Preferably, the reaction time with the second chain extender in step (2) is 2-24 hours.

9. The preparation method according to claim 7 or 8, characterized in that: The preparation method comprises the following steps: (1) mixing a hydroxyl-terminated polymer, a diisocyanate, a catalyst and a solvent, and reacting the mixture at 40-100° C. for 2-24 hours to obtain a prepolymer; (2) The prepolymer obtained in step (1) is mixed with a first chain extender and reacted at 40-100° C. for 2-24 hours, and then a second chain extender is added and mixed at 40-100° C. for 2-24 hours, and the solvent is removed to obtain a polyurethane elastomer.

10. Use of the polyurethane elastomer according to any one of claims 1 to 6 in electronic instruments, protective coatings, flexible wearable devices or smart response materials.

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