High-strength low-temperature-resistant polyurethane material and preparation method thereof

Abstract

The invention provides a high-strength low-temperature-resistant polyurethane material and a preparation method thereof, and belongs to the technical field of polyurethane materials. According to the invention, polyether polyol and diisocyanate are taken as base materials, a hydrazide chain extender is introduced as a first chain extender, multiple hydrogen bonds contained in the first chain extender can form a physical cross-linked network, methacrylic acid modified cyclodextrin is introduced as a second chain extender, and a double-bond polymerization reaction is carried out under the action of an initiator to form a chemical cross-linked network. According to the invention, non-covalent bond multiple hydrogen bonds and covalent cross-linking are combined, and a physical cross-linked network formed by the non-covalent bond multiple hydrogen bonds is dissociated in the deformation process to fully dissipate energy, so that the material keeps excellent tensile property. Covalent cross-linking is mainly concentrated around cyclodextrin molecules, the cross-linking density of the material is improved by improving the double bond modification quantity, the movement of polymer chain segments is not excessively limited, the tensile strength of the polymer is improved, the elongation at break can be kept, the toughness is improved, and meanwhile, good low-temperature resistance is shown.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane materials, and particularly relates to a high-strength and low-temperature resistant polyurethane material and a preparation method thereof. Background Art

[0002] Polyurethane is an excellent organic polymer material with good elasticity, oil resistance and wear resistance, and is widely used in the fields of aerospace, construction, transportation, household appliances and textiles.

[0003] At present, the tensile strength of commonly used polyurethane materials is within 28 - 42 MPa, and there is still room for improvement. Usually, when the tensile strength of polyurethane materials is increased, the elongation at break will be significantly reduced, resulting in a low matching degree between the strength and toughness of the materials, which will limit their application to a certain extent. Therefore, one of the key scientific problems in the field of polyurethane materials is how to ensure the elongation at break while increasing the tensile strength, so as to improve the toughness of the materials. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a high-strength and low-temperature resistant polyurethane material and a preparation method thereof. The present invention can ensure the elongation at break as much as possible while improving the tensile strength of polyurethane, making it have high toughness, and the obtained polyurethane material has the advantages of high strength and low temperature resistance.

[0005] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a high-strength and low-temperature resistant polyurethane material, comprising the following steps:

[0007] Mix polyether diol, diisocyanate, organic solvent and catalyst, and carry out a prepolymerization reaction to obtain a polyurethane prepolymer;

[0008] Dilute the polyurethane prepolymer with an organic solvent, mix the diluted polyurethane prepolymer with a first chain extender, and carry out a first chain extension reaction to obtain a first chain extension product; the first chain extender is a hydrazide-based chain extender;

[0009] Mix the first chain extension product with a second chain extender and a radical initiator, and carry out a second chain extension reaction to obtain a second chain extension product; the second chain extender is methyl methacrylate-modified cyclodextrin;

[0010] Carry out thermal curing on the second chain extension product to obtain a high-strength and low-temperature resistant polyurethane material.

[0011] Preferably, the polyether diol includes polyethylene glycol and / or polytetrahydrofuran diol, and the number average molecular weight of the polyether diol is 1000 - 2000;

[0012] The diisocyanate includes one or more of hexamethylene diisocyanate, p-phenylene diisocyanate and isophorone diisocyanate;

[0013] The catalyst includes organotin catalysts.

[0014] Preferably, the molar ratio of the polyether diol to the diisocyanate is 1:1 to 3;

[0015] The temperature of the prepolymerization reaction is 50 to 80 °C, and the time is 1 to 4 h.

[0016] Preferably, the first chain extender includes succinic dihydrazide and / or adipic dihydrazide;

[0017] The molar ratio of the first chain extender to the polyether polyol is 0.9 to 1:1.

[0018] Preferably, the temperature of the first chain extension reaction is 30 to 60 °C, and the time is 1 to 4 h.

[0019] Preferably, the methacrylic acid-modified cyclodextrin is obtained by an addition reaction of isocyanatoethyl methacrylate and cyclodextrin; the molar ratio of isocyanatoethyl methacrylate to cyclodextrin is 1 to 7:1.

[0020] Preferably, the molar ratio of the second chain extender to the polyether polyol is 0 to 0.1:1, and the value of the second chain extender is not 0.

[0021] Preferably, the radical initiator includes benzoyl peroxide and / or azobisisobutyronitrile;

[0022] The temperature of the second chain extension reaction is 40 to 60 °C, and the time is 1 to 3 h.

[0023] Preferably, the temperature of the thermal curing is 40 to 100 °C, and the time is 24 to 72 h.

[0024] The present invention provides a high-strength and low-temperature resistant polyurethane material prepared by the above preparation method.

[0025] The present invention provides a method for preparing a high-strength low-temperature resistant polyurethane material, which includes the following steps: mixing polyether diol, diisocyanate, organic solvent and catalyst, and carrying out a prepolymerization reaction to obtain a polyurethane prepolymer; diluting the polyurethane prepolymer with an organic solvent, mixing the diluted polyurethane prepolymer with a first chain extender, and carrying out a first chain extension reaction to obtain a first chain extension product; the first chain extender is a hydrazide-based chain extender; mixing the first chain extension product with a second chain extender and a free radical initiator, and carrying out a second chain extension reaction to obtain a second chain extension product; the second chain extender is methyl methacrylate-modified cyclodextrin; carrying out thermal curing on the second chain extension product to obtain a high-strength low-temperature resistant polyurethane material. The polyurethane material prepared by the present invention uses polyether polyol and diisocyanate as the base materials, introduces a hydrazide-based chain extender as the first chain extender, and the multiple hydrogen bonds between the hydrazide-based chain extenders can form a physical crosslinking network. At the same time, methyl methacrylate-modified cyclodextrin is introduced as the second chain extender, and under the action of the free radical initiator, the double bonds on the second chain extender can undergo a polymerization reaction to form a chemical crosslinking network. The present invention combines non-covalent multiple hydrogen bonds and covalent crosslinking. The physical crosslinking network composed of non-covalent multiple hydrogen bonds dissociates during the deformation process to fully dissipate energy, enabling the material to maintain excellent tensile properties. The covalent crosslinking is mainly concentrated around the cyclodextrin molecules, and by increasing the modification amount of its double bonds to increase the crosslinking density of the material, it will not overly restrict the movement of polymer segments. While improving the tensile strength of the polymer, it can maintain its elongation at break, improve toughness, and enable the polymer to obtain good mechanical properties. At the same time, the polyurethane prepared by the present invention can maintain an elongation at break of more than 400% at -50°C, the tensile strength can reach 60 MPa, and it can exhibit good low-temperature resistance.

[0026] Furthermore, the present invention can adjust the proportion of multiple hydrogen bonds and covalent crosslinking components by controlling the proportion of different chain extenders, or adjust the degree of covalent crosslinking by adjusting the modification amount of methyl methacrylate on cyclodextrin, thereby further regulating the mechanical properties of the high-strength low-temperature resistant polyurethane material to meet the usage requirements of different scenarios.

[0027] In addition, the method for preparing the high-strength low-temperature resistant polyurethane material provided by the present invention is simple in operation, low in cost, and easy to realize industrial mass production. Description of the Drawings

[0028] Figure 1 Infrared spectrum of methyl methacrylate-modified cyclodextrin obtained in Example 1;

[0029] Figure 2 Stress-strain curve obtained in Example 1;

[0030] Figure 3 Stress-strain curves of Examples 2-3 at the same tensile rate at -50°C. Detailed implementation mode

[0031] The present invention provides a preparation method of a high-strength low-temperature-resistant polyurethane material, comprising the following steps:

[0032] Mix polyether diol, diisocyanate, organic solvent and catalyst, and carry out a prepolymerization reaction to obtain a polyurethane prepolymer;

[0033] Dilute the polyurethane prepolymer with an organic solvent, mix the diluted polyurethane prepolymer with a first chain extender, and carry out a first chain extension reaction to obtain a first chain extension product; the first chain extender is a hydrazide-based chain extender;

[0034] Mix the first chain extension product with a second chain extender and a free radical initiator, and carry out a second chain extension reaction to obtain a second chain extension product; the second chain extender is a methyl methacrylate-modified cyclodextrin;

[0035] Carry out thermal curing on the second chain extension product to obtain a high-strength low-temperature-resistant polyurethane material.

[0036] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0037] In the present invention, polyether diol, diisocyanate, organic solvent and catalyst are mixed, and a prepolymerization reaction is carried out to obtain a polyurethane prepolymer. In the present invention, the polyether diol includes polyethylene glycol and / or polytetrahydrofuran diol, more preferably polytetrahydrofuran diol; in the present invention, the number average molecular weight of the polyether diol is preferably 1000-2000, and as a specific implementation mode of the present invention, the number average molecular weight of the polyether diol is 1000, 1500 or 2000.

[0038] In the present invention, the diisocyanate preferably includes one or more of hexamethylene diisocyanate, p-phenylene diisocyanate and isophorone diisocyanate, more preferably isophorone diisocyanate.

[0039] In the present invention, the catalyst preferably includes organotin catalysts, further preferably one or more of butyltin oxide, dibutyltin dibutyrate, dibutyltin dilaurate, dimethyltin dibutyrate, dioctyltin dibutyrate and dibutyltin diacetate, more preferably dibutyltin dilaurate. In the present invention, the molar ratio of the polyether diol to the diisocyanate is preferably 1:1-3, specifically 1:1, 1:2 or 1:3.

[0040] In the present invention, the molar ratio of the polyether diol to the catalyst is preferably 1:0.01-0.04, more preferably 1:0.02-0.03.

[0041] In the present invention, the organic solvent preferably includes N,N-dimethylformamide and / or N,N-dimethylacetamide, more preferably N,N-dimethylformamide. In the present invention, the volume ratio of the polyether diol to the organic solvent is preferably 1:0 to 1, and the amount of the organic solvent is not 0.

[0042] The present invention has no special requirements for the mixing method, and the mixing methods well-known to those skilled in the art can be used, such as stirring and mixing.

[0043] In the present invention, the temperature of the prepolymerization reaction is preferably 50 to 80 °C, specifically it can be 50 °C, 60 °C, 70 °C or 80 °C; the time of the prepolymerization reaction is preferably 1 to 4 h, specifically it can be 1 h, 2 h, 3 h or 4 h.

[0044] After the prepolymerization reaction, the present invention preferably does not perform post-treatment on the obtained polyurethane prepolymer and directly proceeds to the next reaction.

[0045] After obtaining the polyurethane prepolymer, the present invention dilutes the polyurethane prepolymer with an organic solvent, mixes the diluted polyurethane prepolymer with a first chain extender, and performs a first chain extension reaction to obtain a first chain extension product. In the present invention, the organic solvent preferably includes N,N-dimethylformamide and / or N,N-dimethylacetamide, more preferably N,N-dimethylformamide. In the present invention, the volume ratio of the polyurethane prepolymer to the organic solvent is preferably 1:1 to 3.

[0046] In the present invention, the first chain extender is a hydrazide-based chain extender. In the present invention, the first chain extender includes succinic dihydrazide and / or adipic dihydrazide, more preferably adipic dihydrazide. In the present invention, the molar ratio of the first chain extender to the polyether polyol is preferably 0.9 to 1:1, more preferably 0.9 to 0.95:1. The present invention has no special requirements for the mixing method, and the mixing methods well-known to those skilled in the art can be used, such as stirring and mixing.

[0047] In the present invention, the temperature of the first chain extension reaction is preferably 30 to 60 °C, specifically it can be 30 °C, 40 °C, 50 °C or 60 °C; the time of the first chain extension reaction is preferably 1 to 4 h, specifically it can be 1 h, 2 h, 3 h or 4 h. The present invention introduces a hydrazide-based chain extender as the first chain extender, and multiple hydrogen bonds between the hydrazide-based chain extenders can form a physical crosslinking network.

[0048] After the first chain extension reaction, the present invention preferably does not perform post-treatment on the obtained first chain extension product and directly proceeds to the next reaction.

[0049] After obtaining the first chain-extended product, the present invention mixes the first chain-extended product with a second chain extender and a free radical initiator to carry out a second chain extension reaction to obtain a second chain-extended product. In the present invention, the second chain extender is a cyclodextrin modified with methacrylic acid. In the present invention, the cyclodextrin modified with methacrylic acid is preferably obtained by an addition reaction of isocyanatoethyl methacrylate and cyclodextrin. In the present invention, the preparation method of the cyclodextrin modified with methacrylic acid preferably includes the following steps:

[0050] Mix isocyanatoethyl methacrylate, cyclodextrin, an organic solvent and an organotin catalyst, and carry out an addition reaction to obtain a cyclodextrin modified with methacrylic acid.

[0051] In the present invention, the organic solvent is preferably one or more of dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide and N-methylpyrrolidone. In the present invention, the organotin catalyst preferably includes one or more of butyltin oxide, dibutyltin dibutyrate, dibutyltin dilaurate, dimethyltin dibutyrate, dioctyltin dibutyrate and dibutyltin diacetate, and more preferably dibutyltin dilaurate.

[0052] In the present invention, the molar ratio of isocyanatoethyl methacrylate to cyclodextrin is preferably 1-7:1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 or 7:1. The present invention adjusts the degree of covalent crosslinking by adjusting the modification amount of methacrylic acid on cyclodextrin, and further regulates the mechanical properties of the high-strength low-temperature resistant polyurethane material. Specifically, as the modification amount of methacrylic acid on cyclodextrin increases, the tensile strength increases and the elongation at break decreases.

[0053] In the present invention, the molar amount of the organotin catalyst is preferably 0.5-1.5% of cyclodextrin, and more preferably 1%.

[0054] The present invention has no special requirements for the mixing method, and the mixing methods well-known to those skilled in the art can be used, specifically such as stirring and mixing. In the present invention, the temperature of the addition reaction is preferably room temperature, and the time is preferably 24-72 h, specifically 24 h, 36 h, 48 h, 60 h or 72 h.

[0055] After the addition reaction, the present invention preferably obtains the cyclodextrin modified with methacrylic acid by a method of adding acetonitrile as an organic solvent for precipitation, and obtains a solid of the cyclodextrin modified with methacrylic acid after vacuum drying.

[0056] The present invention mixes the first chain extension product with a second chain extender and a free radical initiator to carry out a second chain extension reaction to obtain a second chain extension product. In the present invention, the free radical initiator preferably includes benzoyl peroxide and / or azobisisobutyronitrile. In the present invention, the molar ratio of the second chain extender to the polyether polyol is preferably 0 to 0.1:1, more preferably 0.05 to 0.1:1, and the value of the second chain extender is not 0. In the present invention, the molar ratio of the free radical initiator to the polyether polyol is preferably 0.01 to 0.03:1.

[0057] In the present invention, the mixing method is preferably as follows: First, dissolve the second chain extender and the free radical initiator with an organic solvent, and then add them to the first chain extension product. In the present invention, the organic solvent preferably includes N,N-dimethylformamide and / or N,N-dimethylacetamide, more preferably N,N-dimethylformamide.

[0058] In the present invention, the temperature of the second chain extension reaction is preferably 40 to 60 °C, specifically it can be 40 °C, 50 °C or 60 °C; the time of the second chain extension reaction is preferably 1 to 3 h, specifically it can be 1 h, 2 h or 3 h.

[0059] After obtaining the second chain extension product, the present invention performs thermal curing on the second chain extension product to obtain a high-strength low-temperature resistant polyurethane material. The present invention preferably performs the thermal curing in a mold. In the present invention, the temperature of the thermal curing is preferably 40 to 100 °C, specifically it can be 40 °C, 50 °C, 60 °C, 60 °C, 70 °C, 80 °C, 90 °C or 100 °C. In the present invention, the time of the thermal curing is preferably 24 to 72 h, more preferably 36 to 60 h.

[0060] The present invention provides a high-strength low-temperature resistant polyurethane material prepared by the above preparation method.

[0061] The following examples are used to illustrate in detail the high-strength low-temperature resistant polyurethane material and its preparation method provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] The preparation method of the high-strength low-temperature resistant polyurethane material adopts the following steps:

[0064] 1. Dissolve 10 g of cyclodextrin in 20 mL of dimethyl sulfoxide solution, add isocyanatoethyl methacrylate (the molar ratio of cyclodextrin to isocyanatoethyl methacrylate is 1:1), and then add 0.06 g of an organic tin catalyst, and stir and react at room temperature for 24 hours. Add organic solvent acetonitrile to the obtained reaction product for precipitation, and vacuum dry to obtain methacrylate-modified cyclodextrin.

[0065] 2. Add 10 g of polytetrahydrofuran diol with a number-average molecular weight of 2000, 2.22 g of isophorone diisocyanate, and 5 mL of N,N-dimethylformamide into a three-necked flask. Subsequently, add 0.06 g of dibutyltin dilaurate, heat up to 80 °C, and heat and react for 3 hours to obtain a polyurethane prepolymer.

[0066] 3. Add 40 mL of N,N-dimethylformamide to dilute the prepolymer, add 0.8 g of adipic dihydrazide, and react at 40 °C for 1 hour to obtain a first chain extender product. Subsequently, dissolve 1 g of methacrylic acid-modified cyclodextrin and 0.016 g of azobisisobutyronitrile in 20 mL of N,N-dimethylformamide, add them to the first chain extender product, and react at 40 °C for 1 hour to obtain a second chain extender product. Among them, the molar ratio of polytetrahydrofuran diol, adipic dihydrazide, and methacrylic acid-modified cyclodextrin is 1:0.9:0.1.

[0067] 4. Add the second chain extender product into a mold, heat at 80 °C for 48 hours for curing and forming to obtain a polyurethane material.

[0068] The infrared spectrum of the methacrylic acid-modified cyclodextrin obtained in Step 1 is as Figure 1 shown. It can be seen from Figure 1 that the C=C peak at 1655 cm -1 proves the successful modification of methacrylic acid.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that the methacrylic acid-modified cyclodextrin in Step 3 is replaced with cyclodextrin, and the rest of the operations are the same.

[0071] Comparative Example 2

[0072] It is consistent with Steps 1-2 in Example 1. In Step 3, the molar ratio of polytetrahydrofuran diol, adipic dihydrazide, and methacrylic acid-modified cyclodextrin is 1:0.8:0.2, and Step 4 is consistent.

[0073] Comparative Example 3

[0074] It is consistent with Steps 1-2 in Example 1. In Step 3, the molar ratio of polytetrahydrofuran diol, adipic dihydrazide, and methacrylic acid-modified cyclodextrin is 1:0.7:0.3, and Step 4 is consistent.

[0075] Comparative Example 4

[0076] It is consistent with Steps 1-2 in Example 1. In Step 3, the first chain extender is replaced with hexamethylenediamine, and Step 4 is consistent.

[0077] Example 2

[0078] In Step 1 of Example 1, the molar ratio of cyclodextrin to isocyanatoethyl methacrylate is changed to 1:2, and Steps 2 to 4 remain the same.

[0079] Example 3

[0080] In Step 1 of Example 1, the molar ratio of cyclodextrin to isocyanatoethyl methacrylate is changed to 1:3, and Steps 2 to 4 remain the same.

[0081] Performance Test

[0082] (1) The mechanical properties of the polyurethane materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were tested, and the results are shown in Table 1. Among them, the test standard: GB / T 1040-2006, the test speed: 50 mm / min, the test environment: 25 °C, and the toughness of the material is the area under the stress-strain curve. The stress-strain curve obtained in Example 1 is as Figure 2 shown.

[0083] Table 1 Tensile strength, elongation at break, and toughness of the polyurethane materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4

[0084] Serial number Strength (MPa) Elongation at break (%) <![CDATA[Toughness (MJ / m 3 ) <!-- 5 -->]]> Example 1 41.54 1362 242.19 Example 2 53.85 1273 261.23 Example 3 54.32 1156 234.64 Comparative example 1 24.53 1289 110.04 Comparative example 2 41.78 1034 159.90 Comparative example 3 29.34 1071 139.06 Comparative example 4 30.53 832 108.50

[0085] From Figure 2 and the results in Table 1, it can be seen that Example 1 exhibits good tensile strength of 41.54 MPa, high elongation at break of 1362%, and good toughness of 242.19 MJ / m 3 . The mechanical strength, elongation at break, and toughness of Comparative Example 1 are 24.53 MPa, 1289%, and 110.04 MJ / m 3 . Compared with Example 1, the cyclodextrin in Comparative Example 1 is not modified with double bonds and has no covalent cross-linking structure. Therefore, its mechanical properties are worse than those of Example 1.

[0086] By comparing the mechanical properties of the polyurethane films prepared from the cyclodextrin modified with double bonds in Example 1 and the cyclodextrin not modified with double bonds in Comparative Example 1, the tensile strength is increased from 24.53 MPa to over 41.54 MPa. Under the action of multiple hydrogen bonds and covalent cross-linking, the mechanical properties of the polyurethane are enhanced to a certain extent.

[0087] As can be seen from Table 1, the mechanical properties of Comparative Examples 2-3 are lower than those of Example 1. In Example 1 and Comparative Examples 2-3, as the proportion of methacrylic acid-modified cyclodextrin increases, the elongation at break of the prepared polyurethane film decreases from 1362% to 1071%, and the tensile strength decreases from 41.54 MPa to 29.34 MPa. This is mainly because as the proportion of methacrylic acid-modified cyclodextrin increases, the crosslinking between methacrylic acid-modified cyclodextrin molecules increases the crosslinking degree of the polyurethane film, cracks appear inside the polyurethane film, and the uniformity of the prepared film is poor, which affects the phase separation of the hard and soft segments in the polyurethane molecular chain, resulting in poor mechanical properties.

[0088] Next, in Examples 1-3, the molar ratio of adipic dihydrazide and methacrylic acid-modified cyclodextrin was fixed at 9:1, and cyclodextrins with different amounts of double bonds were added to prepare a series of polyurethane films. Compared with the polyurethane film prepared in Comparative Example 1, with a tensile strength of 24.53 MPa and an elongation at break of 1289%, the mechanical properties of the polyurethane films prepared in Examples 1-3 were greatly improved. For example, the tensile strengths of Examples 1-3 were close to 1.69, 2.19, and 2.21 times that of the uncrosslinked film, and the elongation at break remained above 1000%. According to the stress-strain curve, the toughness of the polyurethane film was calculated. The toughness of Examples 1-3 increased from 110.04 MJ / m 3 to 242.19 MJ / m 3 , 261.23 MJ / m 3 and 234.64 MJ / m 3 .

[0089] (2) Examples 2-3 have more excellent mechanical properties. The low-temperature properties of the present invention were characterized. The stress-strain curves of Examples 2-3 at the same tensile rate were tested. The obtained results are as Figure 3 shown. The test standard: GB / T 1040-2006, test speed: 50 mm / min, test environment: -50 °C. The summary of the mechanical properties of Examples 2-3 at the same tensile rate is shown in Table 2.

[0090] Table 2 Tensile strength and elongation at break of Examples 2-3 at -50 °C

[0091] Serial number Strength (MPa) Elongation at break (%) Example 2 62.78 419.37 Example 3 57.06 424.25

[0092] As can be seen from Table 2, at -50 °C, the tensile strengths of the polyurethane materials provided by the present invention are 62.78 MPa and 57.06 MPa respectively, and the elongations at break are 419.37% and 424.25% respectively. They have high tensile strength and good flexibility at low temperature, showing good low-temperature resistance.

[0093] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, low-temperature-resistant polyurethane material, characterized in that: The following steps are involved: The polyether diol, diisocyanate, organic solvent and catalyst are mixed to carry out prepolymerization reaction to obtain a polyurethane prepolymer; The polyurethane prepolymer is diluted with an organic solvent, and the diluted polyurethane prepolymer is mixed with a first chain extender to perform a first chain extension reaction to obtain a first chain extension product; the first chain extender is a hydrazide chain extender; The first chain extension product is mixed with a second chain extender and a free radical initiator to carry out a second chain extension reaction to obtain a second chain extension product; the second chain extender is cyclodextrin modified with methacrylic acid; The second chain extension product is thermally cured to obtain a high-strength and low-temperature-resistant polyurethane material.

2. The preparation method according to claim 1, characterized in that: The polyether diol includes polyethylene glycol and / or polytetrahydrofuran diol, and the number average molecular weight of the polyether diol is 1000-2000; The diisocyanate includes one or more of hexamethylene diisocyanate, p-phenylene diisocyanate and isophorone diisocyanate; The catalyst includes an organotin catalyst.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the polyether diol to the diisocyanate is 1:1 to 3; The prepolymerization reaction is carried out at a temperature of 50 to 80° C. and for a time of 1 to 4 hours.

4. The preparation method according to claim 1, characterized in that: The first chain extender includes succinic acid dihydrazide and / or adipic acid dihydrazide; The molar ratio of the first chain extender to the polyether polyol is 0.9 to 1:

1.

5. The preparation method according to claim 1 or 4, characterized in that: The temperature of the first chain extension reaction is 30-60° C. and the time is 1-4 hours.

6. The preparation method according to claim 1, characterized in that: The methacrylic acid modified cyclodextrin is obtained by addition reaction of isocyanoethyl methacrylate and cyclodextrin; the molar ratio of isocyanoethyl methacrylate to cyclodextrin is 1 to 7:

1.

7. The preparation method according to claim 1 or 6, characterized in that: The molar ratio of the second chain extender to the polyether polyol is 0 to 0.1:1, and the value of the second chain extender is not zero.

8. The preparation method according to claim 1, characterized in that: The free radical initiator includes dibenzoyl peroxide and / or azobisisobutyronitrile; The temperature of the second chain extension reaction is 40-60° C. and the time is 1-3 hours.

9. The preparation method according to claim 1, characterized in that: The thermal curing temperature is 40 to 100° C. and the time is 24 to 72 hours.

10. The high-strength and low-temperature-resistant polyurethane material prepared by the preparation method according to any one of claims 1 to 9.

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