Preparation of polyurethane MXene quantum dot self-repairing elastomer material

Abstract

The invention provides a preparation method of a polyurethane MXene quantum dot self-repairing elastomer material. Wherein the polyurethane elastomer comprises a polyurethane elastomer matrix and MXene quantum dots distributed in the polyurethane elastomer matrix. The MXene quantum dots are introduced into the polyurethane elastomer, so that the tensile strength and the elongation at break of the polyurethane elastomer can be improved, and the mechanical property of the polyurethane elastomer is effectively improved; and the self-repairing efficiency can be obviously enhanced.

Description

Technical Field

[0001] The present invention relates to the field of elastomers, and in particular to the preparation of a polyurethane MXene quantum dot self-healing elastomer material. Background Art

[0002] Polyurethane (PU) is an emerging organic polymer material, known as the "fifth plastic". Due to its excellent performance, it is widely used in many fields such as construction, automobiles, light industry, textiles, petrochemicals, metallurgy, electronics, national defense, medical care, machinery, etc. Polyurethane elastomer is a polymer synthetic material with a large number of carbamate groups on the main chain. It is generally made of oligomer polyols such as polyester, polyether and polyolefin, polyisocyanate and diol or diamine chain extenders. Polyurethane elastomer is a material that combines the properties of rubber and plastic. It has good tensile strength, tear strength, impact resistance, wear resistance, weather resistance, hydrolysis resistance, oil resistance and other advantages. It can be used as structural materials, insulators, soles and solid tires.

[0003] Although polyurethane elastomers have a stable covalent cross-linked network, they will inevitably produce cracks during use, thus affecting performance and service life. Therefore, giving polyurethane elastomers self-healing properties can effectively extend the service life of the material, reduce the consumption of raw materials and environmental pollution, and generate considerable economic and ecological value. Summary of the invention

[0004] The invention provides a polyurethane elastomer having both excellent mechanical strength and good self-repairing effect.

[0005] The invention provides a method for preparing a polyurethane elastomer, which has the advantages of simple operation, repeatable processing and application in large-scale production.

[0006] The present invention provides a polyurethane elastomer, wherein the polyurethane elastomer comprises a polyurethane elastomer matrix and MXene quantum dots distributed in the polyurethane elastomer matrix.

[0007] The polyurethane elastomer as described above, wherein the mass of MXene quantum dots accounts for 0.015%-0.040% of the total mass of the polyurethane elastomer.

[0008] The polyurethane elastomer as described above, wherein the raw materials for preparing the polyurethane elastomer include: polymer polyols, diisocyanate compounds, diol chain extenders, disulfide bond-containing chain extenders and MXene quantum dots.

[0009] The present invention provides a method for preparing the above-mentioned polyurethane elastomer, which comprises the following steps:

[0010] Step 1: Polymerize a polymer polyol and a diisocyanate compound to obtain a prepolymer;

[0011] Step 2: Carry out a chain extension reaction on the prepolymer, a glycol chain extender, a chain extender containing a disulfide bond, and MXene quantum dots to obtain a polyurethane elastomer.

[0012] The preparation method as described above, wherein the molar ratio of the polymer polyol to the diisocyanate compound is 1:(2.8 - 3.5);

[0013] and / or, the molar ratio of the polymer polyol to the glycol chain extender is 1:(1.3 - 1.9);

[0014] and / or, the molar ratio of the polymer polyol to the chain extender containing a disulfide bond is 1:(0.25 - 0.8).

[0015] The preparation method as described above, wherein the polymer polyol is selected from at least one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol;

[0016] and / or, the diisocyanate compound is selected from at least one of xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and polymethylpolyphenyl isocyanate;

[0017] and / or, the glycol chain extender is selected from at least one of resorcinol bis(β-hydroxyethyl) ether and 1,4-butanediol;

[0018] and / or, the chain extender containing a disulfide bond is selected from at least one of 2-hydroxyethyl disulfide, bis(2-aminophenyl) disulfide, cystamine, 3,3'-dithiobispropionic acid, and 4,4'-dithiobisphenol.

[0019] The preparation method as described above, wherein the MXene quantum dots are obtained by the following preparation method:

[0020] Add aluminum carbide titanium to a mixed solution containing lithium fluoride and hydrochloric acid for etching, and adjust the pH to 6.5 - 7.5 to obtain Mxene;

[0021] Add Mxene to a dispersant and disperse it evenly, and prepare MXene quantum dots through a hydrothermal reaction.

[0022] The preparation method as described above, wherein adding Mxene to a dispersant and dispersing it evenly further includes:

[0023] Mix Mxene and an intercalating agent for treatment to obtain intercalated Mxene; add the intercalated Mxene to a dispersant and disperse it evenly.

[0024] The preparation method as described above, wherein the intercalating agent is selected from at least one of tetramethylammonium hydroxide solution and dimethyl sulfoxide;

[0025] and / or, the mass ratio of Mxene to the intercalating agent is 1:(8 - 9);

[0026] and / or, the conditions for the mixing treatment include: the temperature is 20 - 40 °C, and the time is 20 - 30 h.

[0027] The preparation method as described above, wherein the mass ratio of aluminum titanium carbide to the lithium fluoride is 1:(0.9 - 1.1);

[0028] and / or, the conditions for the etching include: the temperature is 40 - 60 °C, and the time is 60 - 80 h;

[0029] and / or, the mass ratio of Mxene to the dispersant is 1:(110 - 130);

[0030] and / or, the conditions for the hydrothermal reaction include: the temperature is 90 - 130 °C, and the time is 5 - 7 hours.

[0031] The present invention provides a polyurethane elastomer, comprising a polyurethane elastomer matrix and MXene quantum dots distributed in the polyurethane elastomer matrix. By introducing MXene quantum dots into the polyurethane elastomer, the tensile strength and elongation at break of the polyurethane elastomer can be improved, thereby effectively enhancing its mechanical properties; and the self - repair efficiency can also be significantly enhanced. Description of the Drawings

[0032] Figure 1 It is the stress - strain curve diagram of the polyurethane elastomer in an embodiment of the present invention;

[0033] Figure 2 It is the microscopic image of the scratch on the polyurethane elastomer before static repair in Example 2 of the present invention;

[0034] Figure 3 It is the microscopic image of the scratch on the polyurethane elastomer after static repair in Example 2 of the present invention;

[0035] Figure 4 It is the microscopic image of the scratch on the polyurethane elastomer before static repair in Example 4 of the present invention;

[0036] Figure 5 It is the microscopic image of the scratch on the polyurethane elastomer after static repair in Example 4 of the present invention;

[0037] Figure 6 It is the microscopic image of the scratch on the polyurethane elastomer before static repair in Example 5 of the present invention;

[0038] Figure 7This is a micrograph of scratches on the polyurethane elastomer after static repair in Example 5 of the present invention;

[0039] Figure 8 This is a micrograph of scratches on the polyurethane elastomer in Example 6 of the present invention before being left to stand for repair;

[0040] Figure 9 This is a micrograph of scratches on the polyurethane elastomer after static repair in Example 6 of the present invention;

[0041] Figure 10 This is a micrograph of scratches on the polyurethane elastomer in Example 7 of the present invention before being left to stand for repair;

[0042] Figure 11 This is a micrograph of scratches on the polyurethane elastomer after static repair in Example 7 of the present invention;

[0043] Figure 12 This is a micrograph of scratches on the polyurethane elastomer in Example 8 of the present invention before being left to stand for repair;

[0044] Figure 13 This is a micrograph of scratches on the polyurethane elastomer after static repair in Example 8 of the present invention;

[0045] Figure 14 This is a graph showing the results of polyurethane elastic self-repairing efficiency in one embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0047] Polyurethane elastomer is a polymer synthetic material with a large number of carbamate groups on the main chain. It is generally made by the gradual addition polymerization of oligomer polyols such as polyester, polyether and polyolefin with polyisocyanate and diol or diamine chain extenders. Polyurethane elastomer has both rubber and plastic properties, and has good tensile strength, tear strength, impact resistance, wear resistance, weather resistance, hydrolysis resistance, oil resistance and other advantages. It can be used as structural materials, insulators, soles and solid tires.

[0048] However, during the use process, cracks will inevitably occur in the polyurethane elastomer, thereby affecting its performance and service life. Therefore, endowing the polyurethane elastomer with self-healing properties can effectively extend the service life of the material. Currently, the preparation methods of self-healing polyurethane elastomers are mainly divided into two categories: extrinsic self-healing and intrinsic self-healing. Among them, extrinsic self-healing realizes self-healing by compounding functional substances inside the material, while intrinsic self-healing realizes self-healing by providing energy to cause covalent or non-covalent interactions in the material itself. In intrinsic self-healing, reversible covalent bonds and reversible non-covalent bonds are two main self-healing mechanisms. For example, self-healing can be achieved by introducing disulfide bonds, Diels-Alder reactions, hydrogen bonds, π-π stacking, ionic interactions, and metal coordination bonds, etc.

[0049] Introducing transition metal carbides and nitrides (Mxene) into the polyurethane elastomer can enhance the mechanical strength and self-healing ability of the polyurethane elastomer. Because MXene itself has high strength and high modulus, which helps to improve the overall mechanical properties of the polyurethane elastomer. By dispersing MXene in the polyurethane elastomer matrix, the tensile strength, tear strength, and wear resistance of the material can be improved. At the same time, the interfacial interactions (such as hydrogen bonds, van der Waals forces) between MXene and polyurethane can promote the closure of cracks, thereby enhancing the self-healing ability of the material. However, the compatibility between MXene and the polyurethane elastomer is poor, resulting in difficulty in uniformly dispersing MXene in the polyurethane elastomer matrix and easy formation of aggregates, which limits the improvement of the performance of the polyurethane elastomer.

[0050] When the lateral size of MXene is less than 10 nm, this semiconductor nanostructure is called MXene quantum dots. MXene quantum dots are emerging materials derived from two-dimensional transition metals, with abundant active edge atoms, good conductivity, and excellent optical properties. MXene quantum dots not only retain the structural characteristics of two-dimensional MXene, but also exhibit more unique properties due to size effects and quantum confinement effects, such as stronger light absorption ability, better conductivity, and biocompatibility, etc. Therefore, introducing MXene quantum dots may be an effective solution.

[0051] Based on the above research, the first aspect of the present invention provides a polyurethane elastomer, which includes a polyurethane elastomer matrix and MXene quantum dots distributed in the polyurethane elastomer matrix.

[0052] The present invention has experimentally found that high-density polar groups such as hydroxyl groups rich in the surface of MXene quantum dots can form a strong hydrogen bond network with amino groups, ester groups, etc. in polyurethane. At the same time, the hydroxyl groups on the surface of MXene quantum dots can also be covalently cross-linked with the isocyanate groups of polyurethane. Through this dual synergistic effect, the interfacial bonding strength is significantly improved, the molecular chain slip is inhibited, and ultimately the performance of the polyurethane elastomer material is enhanced.

[0053] In addition, compared with MXene nanosheets, MXene quantum dots expose more edge functional groups during the preparation process, so MXene quantum dots will form stronger hydrogen bonds with polyurethane molecular chains, effectively improving the tensile strength and elongation at break of polyurethane elastomers; MXene quantum dots also have dense dynamic bond sites on their surface, which can be rapidly reorganized under stimulation such as heating, so introducing MXene quantum dots into polyurethane elastomers can significantly enhance the self-healing efficiency of polyurethane elastomers.

[0054] In the above technical solution, the mass of MXene quantum dots accounts for 0.015%-0.040% of the total mass of the polyurethane elastomer.

[0055] In the experiment, it was found that regulating the mass ratio of MXene quantum dots can effectively enhance the mechanical properties and self-healing efficiency of polyurethane elastomers, and enable polyurethane elastomers to have both excellent mechanical strength and good self-healing efficiency. When the mass ratio of MXene quantum dots is too high, the MXene quantum dots will agglomerate, thereby forming stress concentration points, which will hinder the movement of the molecular chain and cause a decrease in mechanical properties; when the mass ratio of MXene quantum dots is too low, the improvement in mechanical properties is limited, and the self-healing dynamic bonds are insufficient, resulting in a double weakness in mechanical properties and self-healing efficiency. Therefore, when the mass of MXene quantum dots accounts for 0.015%-0.040% of the mass of polyurethane elastomer, MXene quantum dots just have a good matching effect with the polyurethane elastomer matrix, which can maximize the mechanical properties and self-healing efficiency of polyurethane elastomers.

[0056] In a preferred embodiment, the mass of MXene quantum dots accounts for 0.015%-0.025% of the total mass of the polyurethane elastomer. Within this range, the polyurethane elastomer has the most excellent mechanical strength and self-healing efficiency. Specifically, the tensile strength of the polyurethane elastomer can reach 7-9MPa, the elongation at break can reach 800%-1100%, and it has good self-healing efficiency, up to 97.557%.

[0057] In the above technical solution, the raw materials for preparing the polyurethane elastomer include: polymer polyols, diisocyanate compounds, diol chain extenders, disulfide bond-containing chain extenders and MXene quantum dots.

[0058] Among them, polymer polyol is a soft segment component in polyurethane elastomer, usually having a relatively low glass transition temperature, which can endow the material with good flexibility and elasticity. Diisocyanate compounds and diol chain extenders can form the hard segment component in polyurethane elastomer, which can improve the mechanical strength, hardness and chemical resistance of the material. The chain extender containing disulfide bonds can introduce reversible disulfide bonds into the polyurethane chain, endowing the material with self-healing ability and dynamic response characteristics. MXene quantum dots can improve the tensile strength and elongation at break of polyurethane elastomer, and can also significantly enhance its self-healing efficiency.

[0059] To obtain the above-mentioned polyurethane elastomer with good mechanical properties and high self-healing efficiency, the second aspect of the present invention provides a preparation method of polyurethane elastomer, which includes the following steps:

[0060] Step 1: Polymerize polymer polyol and diisocyanate compounds to obtain a prepolymer;

[0061] Step 2: Perform a chain extension reaction on the prepolymer, diol chain extender, chain extender containing disulfide bonds and MXene quantum dots to obtain a polyurethane elastomer.

[0062] In the present invention, a prepolymer is prepared from polymer polyol and diisocyanate compounds, and then the prepolymer is chain-extended with diol chain extender and chain extender containing disulfide bonds to promote the extension of polyurethane chains. At the same time, MXene quantum dots are added to further improve the mechanical properties and self-healing efficiency of polyurethane elastomer. The preparation method provided by the present invention is simple to operate and can be reprocessed, and can be applied to large-scale production. In the present invention, based on the principle of multiple bonding, a cross-linked structure with alternating hard and soft segments is constructed by using a variety of reversible covalent and non-covalent interactions. This design not only endows the material with excellent mechanical properties, but also maintains high self-healing ability. Through the introduction of dynamic covalent bond disulfide bonds and MXene quantum dots, the composite material has excellent repair characteristics and extends the service life of the material. The self-healing efficiency of the obtained polyurethane elastomer is as high as 97.557%.

[0063] Specifically, the polymer polyol and diol chain extender can be placed in a vacuum drying oven in advance for drying, and then the dried polymer polyol and diisocyanate compounds are polymerized to obtain an isocyanate group (NCO)-terminated polyurethane prepolymer.

[0064] Furthermore, step 1 also includes: carrying out a polymerization reaction on a polymer polyol, a diisocyanate compound and a catalyst; wherein, the catalyst can be selected from at least one of dibutyltin dilaurate, triethylamine, and triethylenediamine. The above catalysts can be used to accelerate the reaction between isocyanate and hydroxyl group, and to a certain extent reduce the temperature and time required for the reaction, improve the reaction efficiency and selectivity, thereby improving the purity and performance of the polyurethane elastomer.

[0065] In step 1, the conditions for the polymerization reaction include: the polymerization temperature is 70 - 90 °C, and the polymerization time is 2 - 4 h; such reaction conditions are conducive to the progress of the polymerization reaction. The polymerization reaction can be carried out in an inert atmosphere (such as nitrogen).

[0066] Subsequently, the dried glycol chain extender, the chain extender containing disulfide bonds, and MXene quantum dots are added to the prepared prepolymer for a chain extension reaction.

[0067] The conditions for the chain extension reaction include: the chain extension temperature is 75 - 95 °C, and the chain extension time is 2 - 4 h; such reaction conditions are conducive to the progress of the chain extension reaction and are conducive to obtaining a polyurethane elastomer that meets expectations. The chain extension reaction can be carried out in an inert atmosphere (such as nitrogen).

[0068] After the chain extension reaction is completed, the chain extension reaction product can be taken out and quickly poured into a mold preheated in an oven in advance. The bubbles dissolved in the reaction system are removed by vacuum pumping. After curing to a constant weight, the polyurethane elastomer is obtained.

[0069] Furthermore, to promote the uniform progress of the chain extension reaction, the dried glycol chain extender, the chain extender containing disulfide bonds, and MXene quantum dots can be respectively dissolved in an organic solvent to obtain solution 1, solution 2, and solution 3, and then solution 1, solution 2, and solution 3 are added to the prepolymer for a chain extension reaction.

[0070] Among them, the organic solvent can be selected from at least one of ethyl acetate, toluene, N,N - dimethylacetamide, N,N - dimethylformamide, acetone, and tetrahydrofuran.

[0071] In the above preparation method, since the polyurethane elastomer is a block copolymer composed of soft segments and hard segments, its properties are determined by the interaction between these two segments. Among them, the hard segments are usually formed by the reaction of diisocyanate compounds and glycol chain extenders, and have high mechanical strength and hardness. The microstructure phase separation structure formed by the hard segments and the soft segments can endow the polyurethane elastomer with excellent elasticity and reversible deformation ability. Therefore, by adjusting the ratio of the hard segments to the soft segments, the polyurethane elastomer can be made to have excellent mechanical properties. Controlling the molar ratio of the polymer polyol and the diisocyanate compound or controlling the molar ratio of the polymer polyol and the glycol chain extender helps to control the content of the soft segments and the hard segments at a suitable ratio, thereby helping to improve the mechanical properties of the polyurethane elastomer.

[0072] Through experimental verification, if the mass fraction of the hard segments in the polyurethane elastomer is too low, the polyurethane elastomer is relatively soft; if the mass fraction of the hard segments is too high, the polyurethane elastomer is relatively brittle; and when the mass of the hard segments in the polyurethane elastomer accounts for 27.5%-32.5% of the mass of the polyurethane elastomer, the polyurethane elastomer is moderately hard and soft, and has both toughness and strength.

[0073] Among them, the calculation method of the hard segment content is as follows: hard segment content (%) = S2 / (S1 + S2), where S1 represents the mass fraction of the soft segments based on the total mass of the raw materials, and S2 represents the mass fraction of the hard segments based on the total mass of the raw materials; the total mass of the above raw materials is the total mass of the polymer polyol, the diisocyanate compound, the catalyst, the glycol chain extender, the chain extender containing a disulfide bond, and the MXene quantum dots; the mass of the soft segments is the mass of the polymer polyol; the mass of the hard segments is the mass of the diisocyanate compound, the glycol chain extender, and the chain extender containing a disulfide bond.

[0074] To make the mass of the hard segments account for 27.5%-32.5% of the mass of the polyurethane elastomer, the molar ratio of the polymer polyol and the diisocyanate compound can be limited to 1:(2.8 - 3.5), and the molar ratio of the polymer polyol and the glycol chain extender is 1:(1.3 - 1.9).

[0075] In the above preparation method, the chain extender containing a disulfide bond can introduce disulfide bonds into the polyurethane elastomer. Disulfide bonds have the characteristics of reversible cleavage and recombination. Under external stimuli (such as heat, light, or chemical environment changes), they can be cleaved or reformed. This reversibility enables the material to achieve self-repair after being damaged; at the same time, the dynamic cross-linking characteristics of disulfide bonds also allow the material to relieve stress through the cleavage and recombination of bonds when stressed or damaged, thereby promoting the healing of cracks and enhancing the self-repair of the material. However, through experimental verification, too many disulfide bonds may also cause a decrease in the mechanical properties of the polyurethane elastomer. Only when the mass of the disulfide bonds in the polyurethane elastomer accounts for 2%-5% of the mass of the polyurethane elastomer, the polyurethane elastomer not only has good self-repairability, but also has both toughness and strength.

[0076] Among them, the calculation method of the disulfide bond content is as follows: Disulfide bond content (%) = Ms-s / M0×100%, where Ms-s represents the mass of the chain extender containing disulfide bonds, and M0 represents the total mass of the raw materials; the total mass of the above-mentioned polymer polyol, diisocyanate compound, catalyst, diol chain extender, chain extender containing disulfide bonds, and MXene quantum dots.

[0077] To make the mass of the disulfide bond account for 2%-5% of the mass of the polyurethane elastomer, the molar ratio of the polymer polyol to the chain extender containing disulfide bonds can be limited to 1:(0.25 - 0.8).

[0078] Furthermore, the polymer polyol is selected from at least one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol; the diisocyanate compound is selected from at least one of xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and polymethyl polyphenyl isocyanate; the small molecule diol is selected from at least one of resorcinol bis(β-hydroxyethyl) ether and 1,4-butanediol; the disulfide is selected from at least one of 2-hydroxyethyl disulfide, bis(2-aminophenyl) disulfide, cystamine, 3,3'-dithiobispropionic acid, and 4,4'-dithiobisphenol.

[0079] It can be understood that when the types of any one or more of the polymer polyol, diisocyanate compound, small molecule diol, and disulfide satisfy the above range, the performance of the polyurethane elastomer can be improved.

[0080] In the above preparation method, the MXene quantum dots are obtained through the following preparation method:

[0081] Add aluminum titanium carbide to a mixed solution containing lithium fluoride and hydrochloric acid for etching, and adjust the pH to 6.5 - 7.5 to obtain Mxene;

[0082] Add Mxene to a dispersant and disperse it evenly, and prepare MXene quantum dots through a hydrothermal reaction.

[0083] Specifically, lithium fluoride can be slowly added to the hydrochloric acid solution to form an acidic solution, and then MAX phase material (aluminum titanium carbide) is slowly added thereto for chemical etching to remove the A layer element in the MAX phase and convert the MAX phase into Mxene; the obtained etching solution needs to be washed with deionized water multiple times to remove the residual acid and by-products; then, centrifugation is performed to obtain a solid precipitate, and the solid precipitate is placed in a vacuum oven for drying to obtain MXene powder.

[0084] Furthermore, the mass ratio of aluminum titanium carbide to lithium fluoride is 1:(0.9 - 1.1). By controlling the ratio of aluminum titanium carbide to lithium fluoride, the etching effect can be effectively controlled to obtain MXene with higher purity and better performance.

[0085] Furthermore, the etching conditions include: the temperature is 40 - 60 °C and the time is 60 - 80 h. By controlling the etching conditions, the etching reaction can be accelerated, making the etching reaction more thorough and saving etching time.

[0086] To better obtain Mxene quantum dots and thus improve the mechanical properties and self-healing properties of polyurethane elastomers, Mxene can be induced to undergo a hydrothermal reaction to prepare Mxene quantum dots.

[0087] Specifically, MXene is added to a dispersant and fully dissolved. Then, the dissolved solution is placed in the polytetrafluoroethylene inner liner of a hydrothermal reaction kettle, and an inert gas (such as argon) is introduced to remove the oxygen therein. The inner liner is placed in a stainless steel reaction kettle and put into a blast drying oven for hydrothermal reaction. After the reaction ends, when the reaction kettle cools to room temperature, the reactants are centrifuged and washed, and the upper layer solution is collected. Dialysis treatment is carried out using a dialysis membrane (the cut-off molecular weight can be 1000 Da). During this period, the dialysis water is changed several times until the pH of the solution is close to neutral to obtain a Mxene quantum dot solution. Subsequently, the Mxene quantum dot solution is subjected to freeze-drying treatment to obtain pure Mxene quantum dots.

[0088] Among them, the dispersant can be selected from at least one of water, sodium hydroxide solution, and ammonia water.

[0089] Furthermore, the mass ratio of Mxene to the dispersant can be 1:(110 - 130). By adjusting the addition amount of the dispersant, Mxene can be dispersed evenly, and the hydrothermal reaction can be carried out better.

[0090] Furthermore, the hydrothermal reaction conditions include: the temperature is 90 - 130 °C and the time is 5 - 7 hours. Under these reaction conditions, the synthesized quantum dots have more uniform sizes, which are 1.70 ± 0.31 nm.

[0091] To enable Mxene quantum dots to better improve the mechanical properties and self-healing properties of polyurethane elastomers, Mxene can be modified and then Mxene quantum dots can be prepared; in the present invention, the modification of Mxene is achieved through intercalation.

[0092] That is, the step of adding MXene to a dispersant and dispersing it evenly further includes: mixing MXene and an intercalating agent to obtain intercalated MXene; adding the intercalated MXene to a dispersant and dispersing it evenly.

[0093] Specifically, Mxene and an intercalating agent are mixed (intercalation reaction), and then centrifuged and washed 3-4 times. The solid precipitate is collected and dried in a vacuum oven at 60 °C to obtain intercalated MXene.

[0094] Among them, the intercalating agent is selected from at least one of tetramethylammonium hydroxide solution and dimethyl sulfoxide.

[0095] Furthermore, the mass ratio of Mxene to the intercalating agent is 1:(8-9). By adjusting the ratio of the intercalating agent, the degree and effect of intercalation can be affected.

[0096] Furthermore, the conditions for the mixing treatment include: the temperature is 20-40 °C, and the time is 20-30 h. By controlling the conditions of the mixing treatment, the intercalation reaction can be accelerated, making the intercalation reaction more thorough and saving time.

[0097] Hereinafter, the technical solutions of the present application will be further explained and illustrated in conjunction with specific embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The reagents used, unless otherwise specified, are commercially available or can be obtained through public channels.

[0098] Example 1:

[0099] This example provides a method for preparing a polyurethane elastomer with a hard segment content of 25%, including the following steps:

[0100] (1) Place the condensation reflux device and the three-neck flask in a forced-air drying oven at 80 °C for 2 hours to remove the water molecules attached to the surface. Weigh 20 g of polytetrahydrofuran diol and 1.03 g of 1,4-butanediol, and dry them in a vacuum drying oven at 120 °C for 2 hours.

[0101] (2) Assemble the dried condensation reflux device and the three-neck flask onto a standard synthesis reaction device, and add the dried polytetrahydrofuran diol, 5.71 g of isophorone diisocyanate, and 0.06 g of dibutyltin dilaurate to the three-neck flask. Stir and react at 80 °C for 3 hours under a nitrogen atmosphere to obtain a polyurethane prepolymer terminated with isocyanate groups (NCO).

[0102] (3) Take the dried 1,4-butanediol and add it to 45 mL of the organic mixed solution for stirring and dissolution. The organic mixed solution is obtained by mixing N,N-dimethylformamide and acetone in a volume ratio of 7:1. After all the 1,4-butanediol is dissolved, add the dissolved solution to the NCO-terminated polyurethane prepolymer obtained in step (2) for prepolymer chain extension. Stir and react at 80 °C for 3 hours under a nitrogen atmosphere. Then, take out the three-necked flask from the oil bath and quickly pour it into a mold preheated in an oven at 60 °C in advance. Evacuate the air bubbles dissolved in the reaction system, and cure at 60 °C for 2 - 3 days until a constant weight is obtained to obtain a polyurethane elastomer with a hard segment content of 25%.

[0103] Among them, the calculation method of the hard segment content is as follows: Hard segment content (%) = S2 / (S1 + S2), where S1 represents the mass fraction of the soft segment based on the total mass of the raw materials, and S2 represents the mass fraction of the hard segment based on the total mass of the raw materials; the total mass of the above raw materials is the total mass of polytetrahydrofuran diol, 1,4-butanediol, isophorone diisocyanate, and dibutyltin dilaurate, that is, 26.8 g; the mass of the soft segment is the mass of polytetrahydrofuran diol, that is, 20 g; the mass of the hard segment is the mass of 1,4-butanediol and isophorone diisocyanate, that is, 6.74 g; therefore, S2 is 25.14%, S1 is 74.63%, and the hard segment content is approximately 25%.

[0104] Example 2:

[0105] This example provides a preparation method of a polyurethane elastomer with a hard segment content of 29%. The specific steps can refer to Example 1, and the difference is only that the addition amount of isophorone diisocyanate in this example is 6.72 g, and the addition amount of 1,4-butanediol is 1.376 g.

[0106] Example 3:

[0107] This example provides a preparation method of a polyurethane elastomer with a hard segment content of 35%. The specific steps can refer to Example 1, and the difference is only that the addition amount of isophorone diisocyanate in this example is 8.78 g, and the addition amount of 1,4-butanediol is 2.07 g.

[0108] Test Example 1:

[0109] (1) Conduct a tensile test on the polyurethane elastomers with hard segment contents of 25%, 29%, and 35% in Examples 1 - 3 according to the method specified in GB / T 528 - 2009 to obtain a stress-strain curve ( Figure 1 ).

[0110] Figure 1 The results show that the polyurethane elastomer with a hard segment content of 25% is softer, the polyurethane elastomer with a hard segment content of 35% is more brittle, and the polyurethane elastomer with a hard segment content of 29% has a moderate hardness.

[0111] (2) To detect the self-healing situation of the polyurethane elastomer with a hard segment content of 29%, the polyurethane elastomer with a hard segment content of 29% was prepared into dumbbell-shaped specimens of national standard type 3 as the samples to be detected. Scratches were prefabricated on the surface of the samples to be detected using a blade, and the records were taken by a metallurgical microscope. The tensile strength and elongation at break were detected according to the method specified in GB / T 528-2009, and its self-healing efficiency was calculated. The self-healing efficiency (%) = W1 / W2 × 100%, where W1 represents the tensile strength of the sample to be detected after repair, and W2 represents the original tensile strength of the sample to be detected. The scratched samples to be detected were left standing for repair at 80°C for 4 hours, and the records were taken by a metallurgical microscope, and its tensile strength and elongation at break were detected and its self-healing efficiency was calculated. The microscopic image of the scratches on the samples to be detected before standing for repair is shown Figure 2 , where the scratch diameter at scratch L1 is 7.57 μm; the microscopic image of the scratches on the samples to be detected after standing for repair is shown Figure 3 , where the scratch diameter at scratch L1 is 3.79 μm; the tensile strength and elongation at break of the samples to be detected before and after standing for repair are shown in Table 1, and the result graph of the self-healing efficiency is shown Figure 14 .

[0112] According to the above experimental results, it can be found that the polyurethane elastomer with a hard segment content of 29% has a moderate hardness, but needs to be further optimized to improve the self-healing rate. Therefore, the polyurethane elastomer with a hard segment content of 27.5%-32.5% was selected for subsequent experiments.

[0113] Example 4:

[0114] This example provides a preparation method of a polyurethane elastomer with a disulfide bond content of 1%, including the following steps:

[0115] (1)-(2) The steps are the same as steps (1)-(2) in Example 2;

[0116] (3) Take the dried 1,4-butanediol and add it to 25 mL of N,N-dimethylformamide for stirring and dissolution to obtain solution 1; take 0.42 g of 3,3'-dithiodipropionic acid and add it to 20 mL of N,N-dimethylformamide for stirring and dissolution to obtain solution 2. Heat the standard synthesis reaction equipment in step (2) to 85°C, and then add solution 1 and solution 2 to it to participate in the chain extension of the NCO-terminated polyurethane prepolymer. Stir and react at 85°C for 3 hours under a nitrogen atmosphere. Then take out the three-necked flask from the oil bath and quickly pour it into a mold preheated in an oven at 60°C in advance. The bubbles dissolved in the reaction system are pumped out by vacuum, and it is cured at 60°C for 2-3 days until constant weight to obtain a polyurethane elastomer with a disulfide bond content of 1%.

[0117] Among them, the calculation method of the hard segment content is as follows: Hard segment content (%) = S2 / (S1 + S2), where S1 represents the mass fraction of the soft segment based on the total mass of the raw materials, and S2 represents the mass fraction of the hard segment based on the total mass of the raw materials; the above-mentioned total mass of the raw materials is the total mass of polytetrahydrofuran diol, 1,4-butanediol, isophorone diisocyanate, dibutyltin dilaurate, and 3,3'-dithiobispropionic acid, that is, 28.576 g; the mass of the soft segment is the mass of polytetrahydrofuran diol, that is, 20 g; the mass of the hard segment is the mass of 1,4-butanediol, isophorone diisocyanate, and 3,3'-dithiobispropionic acid, that is, 8.516 g; therefore, S2 is 29.80%, S1 is 69.99%, and the hard segment content is about 30%.

[0118] The calculation method of the disulfide bond content is as follows: Disulfide bond content (%) = M s-s / M0 × 100%, where M s-s represents the mass of the chain extender containing disulfide bonds, and M0 represents the total mass of the raw materials; the above-mentioned total mass of the raw materials is the total mass of polytetrahydrofuran diol, 1,4-butanediol, isophorone diisocyanate, dibutyltin dilaurate, and 3,3'-dithiobispropionic acid, that is, 28.576 g; the mass of the chain extender containing disulfide bonds is 0.42 g; therefore, the disulfide bond content is about 1%.

[0119] Example 5:

[0120] This example provides a method for preparing a polyurethane elastomer with a disulfide bond content of 2%, and the specific steps can refer to Example 4, with the only difference being that the addition amount of 3,3'-dithiobispropionic acid in this example is 0.631 g.

[0121] Example 6:

[0122] This example provides a method for preparing a polyurethane elastomer with a disulfide bond content of 5%, and the specific steps can refer to Example 4, with the only difference being that the addition amount of 3,3'-dithiobispropionic acid in this example is 1.472 g.

[0123] Test Example 2:

[0124] Referring to the method of Test Example 1(2), the self-healing of polyurethane elastomers with disulfide bond contents of 1%, 2%, and 5% in Examples 4 - 6 was detected. The microscopic image of the scratch on the sample to be detected with a disulfide bond content of 1% before static repair is shown Figure 4 , where the scratch diameter at scratch L1 is 7.54 μm; the microscopic image of the scratch on the sample to be detected with a disulfide bond content of 1% after static repair is shown Figure 5 , where the scratch diameter at scratch L1 is 2.33 μm; the microscopic image of the scratch on the sample to be detected with a disulfide bond content of 2% before static repair is shown Figure 6, where the scratch diameter at the scratch L1 is 6.98 μm; the microscopic image of the scratch after static repair of the sample to be tested with a disulfide bond content of 2% is shown Figure 7 , where the scratch diameter at the scratch L1 is 2.36 μm; the microscopic image of the scratch before static repair of the sample to be tested with a disulfide bond content of 5% is shown Figure 8 , where the scratch diameter at the scratch L1 is 7.95 μm; the microscopic image of the scratch after static repair of the sample to be tested with a disulfide bond content of 5% is shown Figure 9 , Figure 9 No obvious scratch is seen; the tensile strength and elongation at break of the above-mentioned sample to be tested before and after static repair are shown in Table 1, and the self-healing efficiency result diagram is shown Figure 14 .

[0125] According to the above experimental results, it can be found that the self-healing of polyurethane elastomers with disulfide bond contents of 2% and 5% is good. Therefore, polyurethane elastomers with disulfide bond contents of 2%-5% are selected for subsequent experiments.

[0126] Example 7:

[0127] This example provides a preparation method of a self-healing polyurethane elastomer, which includes the following steps:

[0128] (1). Take 2.00 g of lithium fluoride powder and slowly add it to 40 mL of 1 M dilute hydrochloric acid solution, and then slowly add 2.00 g of lithium titanium carbide powder to it. Stir magnetically at 50 °C for 72 h to obtain an etching solution. Wash the etching solution repeatedly until the pH is neutral, collect the solid precipitate, place it in a vacuum oven and dry it at 60 °C for 24 h to obtain MXene powder. Take 1 g of MXene powder and add it to 10 mL of 25 wt% tetramethylammonium hydroxide solution, stir at 30 °C for 1 day, centrifuge and wash 3-4 times, collect the solid precipitate, place it in a vacuum oven and dry it at 60 °C to obtain the intercalated MXene powder.

[0129] (2). Take 0.2 g of the intercalated MXene powder and add it to 25 mL of 1 M sodium hydroxide solution to dissolve it completely. Place the dissolved solution in the polytetrafluoroethylene inner liner of a 50 mL hydrothermal reaction kettle, introduce argon for 2 h to remove the oxygen in it, and then place the inner liner in a stainless steel reaction kettle and put it into a forced air drying oven to react at 100 °C for 6 hours. After the reaction is completed, wait for the reaction kettle to cool to room temperature, wash the reactants under a centrifugal force of 10,000 rpm, collect the upper layer solution, and perform dialysis treatment with a dialysis membrane (cut-off molecular weight of 1000 Da) for more than 24 hours. During this period, change the dialysis water several times until the pH of the solution is close to neutral to obtain an MXene quantum dot solution. Perform freeze-drying treatment on the MXene quantum dot solution to obtain pure MXene quantum dots with a mass of 40 mg.

[0130] (3)-(4) The steps are the same as steps (1)-(2) in Example 5;

[0131] (5) Take the dried 1,4-butanediol and add it to 25 mL of N,N-dimethylformamide for stirring and dissolution to obtain Solution 1; take 1.631 g of 3,3'-dithiobispropionic acid and add it to 20 mL of N,N-dimethylformamide for stirring and dissolution to obtain Solution 2; take the pure MXene quantum dots prepared in step (2) and place them in 20 mL of N,N-dimethylformamide solution for stirring and dissolution to obtain Solution 3. Heat the standard synthesis reaction equipment in step (4) to 85 °C, and then add Solution 1, Solution 2, and 3 mL of Solution 3 to it to participate in the chain extension of the NCO-terminated polyurethane prepolymer. Stir and react at 85 °C for 3 hours under a nitrogen atmosphere. Then, take out the three-necked flask from the oil bath and quickly pour it into a mold preheated in an oven at 60 °C in advance. Evacuate the air bubbles dissolved in the reaction system, and cure at 60 °C for 2-3 days until constant weight to obtain a polyurethane elastomer with a mass of 28.492 g.

[0132] In the polyurethane elastomer, the calculation method of the hard segment content is as follows: Hard segment content (%) = S2 / (S1 + S2), where S1 represents the mass fraction of the soft segment based on the total mass of the raw materials, and S2 represents the mass fraction of the hard segment based on the total mass of the raw materials; the above total mass of the raw materials is the total mass of polytetrahydrofuran diol, 1,4-butanediol, isophorone diisocyanate, dibutyltin dilaurate, 3,3'-dithiobispropionic acid, and MXene quantum dots, which is 28.793 g; the mass of the soft segment is the mass of polytetrahydrofuran diol, which is 20 g; the mass of the hard segment is the mass of 1,4-butanediol, isophorone diisocyanate, and 3,3'-dithiobispropionic acid, which is 8.727 g; therefore, S2 is 30.31%, S1 is 69.46%, and the hard segment content is approximately 30%.

[0133] The calculation method of the disulfide bond content is as follows: Disulfide bond content (%) = M s-s / M0 × 100%, where M s-s represents the mass of the chain extender containing disulfide bonds, and M0 represents the total mass of the raw materials; the above total mass of the raw materials is the total mass of polytetrahydrofuran diol, 1,4-butanediol, isophorone diisocyanate, dibutyltin dilaurate, 3,3'-dithiobispropionic acid, and MXene quantum dots, which is 28.793 g; the mass of the chain extender containing disulfide bonds is 0.631 g; therefore, the disulfide bond content is approximately 2%.

[0134] Example 8:

[0135] This embodiment provides a method for preparing a self-healing polyurethane elastomer. The specific steps can be referred to in Example 7, with the only difference being that the addition amount of the dissolution solution 3 in this embodiment is 5 mL, and the mass of the obtained polyurethane elastomer is 28.492 g.

[0136] Test Example 3:

[0137] Referring to the method of Test Example 1(2), the self-healing situation of the self-healing polyurethane elastomers in Examples 7-8 was detected. The microscopic image of the scratch on the sample to be detected in Example 7 before static repair is shown Figure 10 , where the scratch diameter at the scratch L1 is 7.57 μm; the microscopic image of the scratch on the sample to be detected in Example 7 after static repair is shown Figure 11 , Figure 11 and no obvious scratch is seen; the microscopic image of the scratch on the sample to be detected in Example 8 before static repair is shown Figure 12 , where the scratch diameter at the scratch L1 is 7.21 μm; the microscopic image of the scratch on the sample to be detected in Example 8 after static repair is shown Figure 13 , Figure 13 and no obvious scratch is seen; the tensile strength and elongation at break of the above samples to be detected before and after static repair can be seen in Table 1, and the result graph of the self-healing efficiency is shown Figure 14 .

[0138] Table 1

[0139]

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polyurethane elastomer, characterized in that, The polyurethane elastomer includes a polyurethane elastomer matrix and MXene quantum dots distributed in the polyurethane elastomer matrix.

2. The polyurethane elastomer according to claim 1, wherein, The mass of the MXene quantum dots accounts for 0.015%-0.040% of the total mass of the polyurethane elastomer.

3. The polyurethane elastomer according to claim 1 or 2, characterized in that, The raw materials for preparing the polyurethane elastomer include: polymer polyol, diisocyanate compound, glycol chain extender, chain extender containing disulfide bond, and MXene quantum dots.

4. The preparation method of the polyurethane elastomer according to any one of claims 1-3, characterized in that, It includes the following steps: Step 1, polymerize the polymer polyol and the diisocyanate compound to obtain a prepolymer; Step 2, perform a chain extension reaction on the prepolymer, the glycol chain extender, the chain extender containing disulfide bond, and the MXene quantum dots to obtain the polyurethane elastomer.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the polymer polyol to the diisocyanate compound is 1:(2.8-3.5); and / or, the molar ratio of the polymer polyol to the glycol chain extender is 1:(1.3-1.9); and / or, the molar ratio of the polymer polyol to the chain extender containing disulfide bond is 1:(0.25-0.8).

6. The preparation method according to claim 4 or 5, characterized in that The polymer polyol is selected from at least one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol; and / or, the diisocyanate compound is selected from at least one of xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and polymethylpolyphenyl isocyanate; and / or, the glycol chain extender is selected from at least one of resorcinol bis(β-hydroxyethyl) ether and 1,4-butanediol; and / or, the chain extender containing disulfide bond is selected from at least one of 2-hydroxyethyl disulfide, bis(2-aminophenyl) disulfide, cystamine, 3,3'-dithiobispropionic acid, and 4,4'-dithiobisphenol.

7. The preparation method according to any one of claims 4-6, characterized in that, The MXene quantum dots are obtained by the following preparation method: Add aluminum titanium carbide to a mixed solution containing lithium fluoride and hydrochloric acid for etching, and adjust the pH to 6.5-7.5 to obtain Mxene; Add Mxene to a dispersant and disperse it evenly, and prepare MXene quantum dots through a hydrothermal reaction.

8. The preparation method according to claim 7, characterized in that, The step of adding Mxene to a dispersant and dispersing it evenly further includes: Mix Mxene and an intercalating agent to obtain intercalated Mxene; add the intercalated Mxene to a dispersant and disperse it evenly.

9. The preparation method according to claim 8, characterized in that, The intercalating agent is selected from at least one of tetramethylammonium hydroxide solution and dimethyl sulfoxide; and / or, the mass ratio of Mxene to the intercalating agent is 1:(8-9); and / or, the conditions for the mixing treatment include: temperature is 20-40°C, and time is 20-30h.

10. The preparation method according to claim 8 or 9, characterized in that, The mass ratio of aluminum titanium carbide to lithium fluoride is 1:(0.9-1.1); and / or, the conditions for the etching include: temperature is 40-60°C, and time is 60-80h; and / or, the mass ratio of Mxene to the dispersant is 1:(110-130); and / or, the conditions for the hydrothermal reaction include: temperature is 90-130°C, and time is 5-7 hours.

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