Self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcing and toughening as well as preparation method and application of self-repairing waterborne polyurethane composite elastomer

Abstract

The invention relates to a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcing and toughening as well as a preparation method and application thereof, and belongs to the technical field of self-repairing high polymer materials. The method comprises the following steps: preparing a waterborne polyurethane emulsion; the preparation method comprises the following steps: uniformly dispersing polyvinylpyrrolidone in an ethanol solution, adding polyfunctional mercaptan and polyfunctional isocyanate, and adding an amino-containing imidazole monomer to obtain microsphere powder; and uniformly dispersing the microsphere powder in a waterborne polyurethane emulsion, adding a metal salt solution, and then volatilizing water to form a film material, thereby obtaining the self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening. The self-repairing waterborne polyurethane elastomer with excellent comprehensive performance is obtained by designing the structure of waterborne polyurethane, modifying the surface of the microsphere and introducing a dynamic interface for compounding, and the strength, the toughness and the self-repairing capability of the elastomer are simultaneously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of self-repairing polymer materials, and specifically relates to a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, and a preparation method and application thereof. Background Art

[0002] Endowing polymer materials with self-healing capabilities can indeed significantly improve their service life, safety and stability. However, there is a contradiction between the mechanical strength and self-healing properties of self-healing polymers. For example, materials with stronger chemical bonds tend to have higher mechanical strength, but due to the dynamics of chemical bonds and poor chain fluidity, it is difficult to achieve self-healing. On the contrary, although materials based on weaker chemical bonds can achieve self-healing, their mechanical properties are usually lower. This is because the breaking of weak sacrificial bonds requires less energy, making the material prone to deformation when subjected to external forces, thereby reducing its mechanical strength. Therefore, how to strike a balance between the two becomes the key.

[0003] In practical applications, materials are usually required to have comprehensive properties, such as high mechanical properties, good conductivity, mild repair conditions, environmental tolerance, and synergistic repair of electrical and mechanical properties. Therefore, how to design and synthesize materials with both high mechanical strength and excellent self-healing properties is a challenging problem. In order to overcome this challenge, researchers have proposed a variety of strategies to improve the mechanical strength of self-healing polymers. For example, by introducing dynamic cross-linking structures or supramolecular interactions, rapid reorganization after damage can be achieved without sacrificing mechanical strength; self-reinforced polyurethane elastomers induced by aromatic disulfides can achieve self-healing properties while still ensuring high tensile strength and toughness of the material; hierarchical hydrogen bonding interactions and metal coordination can enhance the mechanical strength of self-healing elastomers; adding fillers to elastomers improves their mechanical properties such as elastic modulus and fracture toughness; these methods demonstrate the possibility of simultaneously improving mechanical strength and self-healing ability by rationally designing molecular structures and interaction forces. In short, solving the contradiction between mechanical strength and self-healing properties in self-healing polymers is one of the current research focuses. Through innovative molecular design and interaction mechanisms, the comprehensive performance of materials can be effectively improved to meet the needs of engineering applications. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention mainly solves the contradictory problem that the strength-toughness and strength-self-repairing performance of elastomer materials cannot be improved synergistically. The present invention provides a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, and its preparation method and application. The present invention designs the structure of waterborne polyurethane, modifies the surface of microspheres, introduces a dynamic interface and composites the two, thereby obtaining a self-repairing waterborne polyurethane elastomer with excellent comprehensive performance, and achieving simultaneous improvement of the strength, toughness and self-repairing ability of the elastomer.

[0005] The first object of the present invention is to provide a method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, comprising the following steps:

[0006] preparing a waterborne polyurethane emulsion;

[0007] The polyvinyl pyrrolidone is uniformly dispersed in an ethanol solution, a multifunctional thiol and a multifunctional isocyanate are added, and after reacting for 2 to 4 hours, an amino-containing imidazole monomer is added, and the reaction is continued for 12 hours or more to obtain a microsphere powder;

[0008] The microsphere powder is uniformly dispersed in an aqueous polyurethane emulsion, a metal salt solution is added, and then the water is volatilized to form a membrane material, thereby obtaining a self-repairing aqueous polyurethane composite elastomer based on dynamic interface reinforcement and toughening;

[0009] Wherein, the metal salt is one or more of 4-fluorophenylmagnesium chloride, 1,3-dioxolane-2-ethylmagnesium bromide, bis(trifluoromethanesulfonyl)imide zinc, 2-mercaptobenzothiazole zinc salt, zinc trifluoromethanesulfonate, zinc acetate, and ferric chloride.

[0010] Preferably, the mass proportion of the microsphere powder in the reaction system is 1wt% to 30wt%; the molar ratio of the metal salt to the amino-containing imidazole monomer is 1:4-7.

[0011] Preferably, the multifunctional thiol is one of trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), tetrakis(3-mercaptopropionic acid) pentaerythritol ester, and tetrakis(3-mercaptobutyric acid) pentaerythritol ester, and its structural formula is as follows:

[0012]

[0013] Preferably, the multifunctional isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate, and its structural formula is as follows:

[0014]

[0015] The isocyanate functional groups are in excess of 10-30% relative to the mercapto functional groups.

[0016] Preferably, the amino-containing imidazole monomer is one or more of 2-(2-methyl-1H-imidazol-1-yl)ethylamine, 1-(3-amino-propyl)imidazole, 2-(1H-imidazol-1-yl)ethylamine, 4-(2-methyl-1H-imidazole)benzylamine, and 1H-imidazole-2-methylamine, and the structural formula thereof is as follows:

[0017]

[0018] Preferably, the aqueous polyurethane emulsion is prepared according to the following steps:

[0019] After mixing diisocyanate, polyether polyol and catalyst, adding organic solvent, heating to 70-80°C for reaction for 1-4h, adding carboxylic acid hydrophilic chain extender for reaction for 2-3h, then adding small molecule chain extender containing disulfide bond for reaction for 2-3h, then cooling to 40-50°C, adding small molecule amine chain extender containing imidazole group for reaction for 3-4h, cooling to 30-35°C, adding organic solvent for dilution, then adding neutralizer for reaction for 0.5-1h, then adding water solvent for stirring and emulsification to obtain the primary product;

[0020] The organic solvent is removed from the initial product by distillation under reduced pressure to obtain an aqueous polyurethane emulsion;

[0021] The catalyst is one of dibutyltin dilaurate, stannous octoate and bismuth isooctanoate.

[0022] Preferably, the diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate;

[0023] The polyether polyol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol;

[0024] The organic solvent is one or more of acetone, N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone.

[0025] Preferably, the carboxylic acid hydrophilic chain extender is dimethylol propionic acid and / or dimethylol butyric acid;

[0026] The small molecule chain extender containing a disulfide bond is a small molecule alcohol chain extender containing a disulfide bond or a small molecule amine chain extender containing a disulfide bond;

[0027] The small molecule amine chain extender containing imidazole groups is one or more of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,2-diaminoimidazole, and 4-amino-5-imidazolecarboxamide;

[0028] The neutralizing agent is one or more of triethylamine, N,N-dimethylethanolamine, diethanolamine and triethanolamine.

[0029] The second object of the present invention is to provide a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

[0030] The third object of the present invention is to provide a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening and its application in the field of self-repairing polymer materials

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] The present invention provides a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, and a preparation method and application thereof. The present invention adopts high-elasticity and high-modulus microspheres to design the structure of waterborne polyurethane, introduces a small molecule chain extender containing imidazole, and obtains an imidazole-functionalized waterborne polyurethane matrix; by adding metal ions, the imidazole-functionalized microspheres and the imidazole-functionalized matrix are compounded, and the coordination crosslinking effect of imidazole / metal and the high elasticity and high modulus properties of the microspheres achieve further improvement in the strength of the matrix.

[0033] The present invention modifies the surface of the microspheres so that a dynamic interface is formed between the microspheres and the matrix through the imidazole-metal coordination effect, thereby establishing an efficient stress transfer and energy dissipation mechanism, improving the energy dissipation capacity of the material during the stretching process, and further improving the toughness of the material.

[0034] The present invention designs the structure of waterborne polyurethane and introduces dynamic disulfide bonds to give the matrix self-healing properties. At the same time, based on the reversibility of the dynamic interface metal coordination bonds between the microspheres and the matrix, when the material is damaged, the material's repair ability can be further enhanced through the breaking and recombination of the dynamic bonds.

[0035] Compared with directly adding microspheres, the formation of the dynamic interface in the present invention can greatly improve the dispersibility and compatibility of the microspheres in the matrix, significantly improve the interface bonding degree between the two phases, enhance the interface stress transfer effect, effectively inhibit crack propagation, and thus improve the comprehensive performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The invention relates to a stress-strain curve of a self-healing waterborne polyurethane elastomer and a waterborne polyurethane matrix thereof that are enhanced and toughened based on a dynamic interface, wherein the addition amount of microspheres is 2wt%, and the ratio of metal salt to amino-containing imidazole monomer is 1:4.

[0037] Figure 2 It is a DSC curve of a self-healing waterborne polyurethane elastomer and its waterborne polyurethane matrix based on a dynamic interface reinforcement and toughening, wherein the addition amount of microspheres is 2wt%, and the ratio of metal salt to amino-containing imidazole monomer is 1:4.

[0038] Figure 3 This is a microscope image of artificial scratches on the surface of a self-healing waterborne polyurethane elastomer based on enhanced toughness of a dynamic interface repaired at 80°C for 0h and 5h, with a magnification of 25. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific embodiments, but it should be understood that the embodiments listed are only for facilitating understanding of the core method and application field of the present invention, but the scope of the present invention is not limited thereto.

[0040] The purpose of the present invention is to provide a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, and its preparation method and application. The present invention mainly utilizes the high elasticity and high modulus properties of microspheres and the dynamic interface formed with the waterborne polyurethane matrix to jointly improve the mechanical properties and self-repairing properties of the elastomer, solving the contradiction that the strength-toughness and strength-self-repairing properties of the material cannot be synergistically improved.

[0041] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, comprising the following steps:

[0042] preparing a waterborne polyurethane emulsion;

[0043] The polyvinyl pyrrolidone is uniformly dispersed in an ethanol solution, a multifunctional thiol and a multifunctional isocyanate are added, and after reacting for 2 to 4 hours, an amino-containing imidazole monomer is added, and the reaction is continued for 12 hours or more to obtain a microsphere powder;

[0044] The microsphere powder is uniformly dispersed in an aqueous polyurethane emulsion, a metal salt solution is added, and then the water is volatilized to form a membrane material, thereby obtaining a self-repairing aqueous polyurethane composite elastomer based on dynamic interface reinforcement and toughening;

[0045] Wherein, the metal salt is one or more of 4-fluorophenylmagnesium chloride, 1,3-dioxolane-2-ethylmagnesium bromide, bis(trifluoromethanesulfonyl)imide zinc, 2-mercaptobenzothiazole zinc salt, zinc trifluoromethanesulfonate, zinc acetate, and ferric chloride.

[0046] The microsphere powder prepared by the present invention is an imidazole-functionalized high-elasticity and high-modulus microsphere; the present invention uses imidazole-functionalized high-elasticity and high-modulus microspheres to construct a dynamic interface with an aqueous polyurethane containing imidazole functional groups and dynamically reversible disulfide bonds through imidazole-metal coordination to obtain a reinforced and toughened self-healing elastomer. Specifically, it includes: firstly, isocyanate-functionalized microspheres are obtained by dispersion polymerization, and then reacted with amino-containing imidazole monomers to obtain imidazole-functionalized high-elasticity and high-modulus microspheres; the structure of the aqueous polyurethane is designed, and a chain extender containing disulfide bonds and imidazole is gradually introduced to obtain an imidazole-functionalized aqueous polyurethane matrix with self-healing ability; after the microspheres are compounded with the matrix, metal ions are added to produce a coordination effect, so that a dynamic interface is formed between the microspheres and the matrix. On the one hand, the high-elasticity and high-modulus microspheres can improve the strength of the elastomer as reinforcing fillers; on the other hand, the metal / imidazole coordination effect enhances the interfacial bonding force between the microspheres and the matrix, increases the crosslinking density of the system, and thus improves the strength of the elastomer. In addition, the metal / imidazole coordination bond is dynamically reversible and can break and reorganize during the stretching process, dissipating a large amount of energy, further improving the toughness and self-healing properties of the elastomer. The present invention utilizes the high elasticity and high modulus properties of the microspheres and the dynamic interface formed with the waterborne polyurethane matrix to jointly improve the mechanical properties and self-healing properties of the elastomer, solving the contradiction that the strength-toughness and strength-self-healing properties of the material cannot be synergistically improved.

[0047] The mass proportion of the microsphere powder in the reaction system is 1wt% to 30wt%; the molar ratio of the metal salt to the amino-containing imidazole monomer in the system is 1:4 to 7.

[0048] The multifunctional thiol is one of trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), tetrakis(3-mercaptopropionate) pentaerythritol ester, and tetrakis(3-mercaptobutyrate) pentaerythritol ester, and its structural formula is as follows:

[0049]

[0050] The multifunctional isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate, and its structural formula is as follows:

[0051]

[0052] The isocyanate functional groups are in excess of 10-30% relative to the mercapto functional groups.

[0053] The amino-containing imidazole monomer is one or more of 2-(2-methyl-1H-imidazol-1-yl)ethylamine, 1-(3-amino-propyl)imidazole, 2-(1H-imidazol-1-yl)ethylamine, 4-(2-methyl-1H-imidazole)benzylamine, and 1H-imidazole-2-methylamine, and the structural formula thereof is as follows:

[0054]

[0055] According to the present invention, the aqueous polyurethane emulsion is prepared according to the following steps:

[0056] After mixing diisocyanate, polyether polyol and catalyst, adding organic solvent, heating to 70-80°C for reaction for 1-4h, adding carboxylic acid hydrophilic chain extender for reaction for 2-3h, then adding small molecule chain extender containing disulfide bond for reaction for 2-3h, then cooling to 40-50°C, adding small molecule amine chain extender containing imidazole group for reaction for 3-4h, cooling to 30-35°C, adding organic solvent for dilution, then adding neutralizer for reaction for 0.5-1h, then adding water solvent for stirring and emulsification to obtain the primary product;

[0057] The organic solvent is removed from the initial product by distillation under reduced pressure to obtain an aqueous polyurethane emulsion;

[0058] The catalyst is one of dibutyltin dilaurate, stannous octoate and bismuth isooctanoate.

[0059] The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate;

[0060] The polyether polyol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol;

[0061] The organic solvent is one or more of acetone, N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone.

[0062] The carboxylic acid hydrophilic chain extender is dimethylol propionic acid and / or dimethylol butyric acid;

[0063] The disulfide-bonded small molecule chain extender is a disulfide-bonded small molecule alcohol chain extender or a disulfide-bonded small molecule amine chain extender, specifically including: one or more of 2,2'-diaminodiphenyl disulfide, 4,4'-diaminodiphenyl disulfide, 4,4'-dihydroxydiphenyl disulfide, and 3,3'-dihydroxydiphenyl disulfide, and the structural formula thereof is as follows:

[0064]

[0065] The small molecule amine chain extender containing imidazole groups is one or more of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,2-diaminoimidazole, and 4-amino-5-imidazolecarboxamide, and its structural formula is as follows:

[0066]

[0067] The neutralizing agent is one or more of triethylamine, N,N-dimethylethanolamine, diethanolamine and triethanolamine.

[0068] In one embodiment, a method for preparing a dynamic interface-based enhanced toughened self-healing waterborne polyurethane elastomer comprises imidazole-functionalized high-elasticity and high-modulus microspheres, waterborne polyurethane containing imidazole functional groups and dynamically reversible disulfide bonds, and metal salts; the imidazole-functionalized high-elasticity and high-modulus microspheres construct a dynamic interface with waterborne polyurethane containing imidazole functional groups and dynamically reversible disulfide bonds through imidazole-metal coordination to obtain an enhanced toughened self-healing elastomer, and the specific preparation steps are as follows:

[0069] Step 1: Preparation of imidazole functionalized high elasticity and high modulus microspheres: Ultrasonic dispersion of polyvinyl pyrrolidone in ethanol solution, transfer to a three-necked flask, start magnetic stirring, mix multifunctional thiol and multifunctional isocyanate and add to the three-necked flask to react for 2 hours, wherein the isocyanate functional group is 10-30% excess relative to the thiol functional group; continue to add amino-containing imidazole monomers to react for more than 12 hours. The obtained product is centrifuged and washed several times and freeze-dried for 48 hours to obtain dry microsphere powder.

[0070] Step 2: Preparation of self-healing water-based polyurethane emulsion: After mixing diisocyanate, polyether polyol and catalyst, add them into a three-necked flask and add a small amount of organic solvent, heat to 70-80°C and react for 2 hours to obtain an isocyanate-terminated prepolymer; the catalyst used is any one of dibutyltin dilaurate, stannous octoate, and bismuth isooctanoate, and the organic solvent is any one of acetone, N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone; then add a carboxylic acid hydrophilic chain extender and continue to react for 2-3 hours; then add a small molecule alcohol or amine chain extender containing a disulfide bond and continue to react for 2-3 hours; cool to 40-50°C, add a small molecule amine chain extender containing an imidazole group and continue to react for 3-4 hours; cool to 30-35°C, add acetone to dilute, then add a neutralizer and continue to react for 0.5-1 hour, add deionized water and stir at high speed to emulsify to obtain the initial product, and distill it under reduced pressure to remove acetone to obtain a water-based polyurethane emulsion.

[0071] Step 3: Preparation of self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening: Ultrasonic disperse the microspheres in the obtained waterborne polyurethane emulsion, and after sufficient mixing, add a deionized water solution of metal salt dropwise. After the addition is completed, place the obtained solution in a drying oven to evaporate the water until the membrane material has a constant weight, thereby obtaining a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

[0072] The mass proportion of the imidazole-functionalized high-elasticity and high-modulus microspheres in the entire system is 1wt% to 30wt%; the molar ratio of the metal salt to the amino-containing imidazole monomer is 1:4-7.

[0073] The second aspect of the present invention provides a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

[0074] The third aspect of the present invention provides an application of a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening in the field of self-repairing polymer materials.

[0075] It should be noted that the experimental methods and detection methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0076] Example 1

[0077] 5 g of polyvinyl pyrrolidone was ultrasonically dispersed in 100 g of ethanol and added to a three-necked flask and magnetic stirring was started. 3.33 g of isophorone diisocyanate and 4.78 g of trimethylolpropane tris(3-mercaptopropionate) were mixed and stirred, then added to the three-necked flask and reacted at room temperature for 2 h. 0.56 g of 1-vinylimidazole was added and the reaction was continued for 12 h. The obtained product was centrifuged and washed 3 times and then freeze-dried for 48 h to obtain dry microspheres.

[0078] 3.0 g of polytetrahydrofuran diol and 0.16 g of 2,2-dimethylol propionic acid were vacuum dried at 120° C. for 2 h. In a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.33 g of isophorone diisocyanate, and 30 μL of dibutyltin dilaurate were added to a three-necked flask equipped with a condenser, and the mixture was heated to 80° C. and mechanically stirred for 2 h. Then 2,2-dimethylol propionic acid was added, and the reaction was continued at 80° C. for 2 h. The temperature was lowered to 60° C., and 0.25 g of 4,4'-diaminodiphenyl disulfide was added in a nitrogen atmosphere, and the reaction was continued at 60° C. for 2 h. The temperature was lowered to 40° C., and 0.18 g of 2-(4-aminophenyl)-5-aminobenzimidazole, continue to react at 40°C for 2h; cool to 35°C, add acetone to the reaction system for dilution, and continue to add 0.2ml triethylamine for 0.5h; add 12ml deionized water, stir at a speed of 3000rpm until completely emulsified, and finally remove acetone by vacuum distillation to obtain a waterborne polyurethane emulsion;

[0079] Microspheres with a solid content of 2 wt% were added to the aqueous polyurethane emulsion and ultrasonically stirred evenly. A deionized water solution of 0.1 mol / L zinc trifluoromethanesulfonate was added dropwise. The molar ratio of the metal salt to the imidazole functional group in the reaction system was 1:5. After the addition was completed, the mixture was magnetically stirred for 12 hours. After sufficient reaction, it was placed in a drying oven and dried at 60°C for 24 hours, and then further vacuum dried for 12 hours to obtain a self-healing waterborne polyurethane composite material.

[0080] Example 2

[0081] 5 g of polyvinyl pyrrolidone was ultrasonically dispersed in 100 g of ethanol and added to a three-necked flask and magnetic stirring was started. 3.33 g of isophorone diisocyanate and 4.78 g of trimethylolpropane tris(3-mercaptopropionate) were mixed and stirred, then added to the three-necked flask and reacted at room temperature for 2 h. 0.56 g of 1-vinylimidazole was added and the reaction was continued for 12 h. The obtained product was centrifuged and washed 3 times and then freeze-dried for 48 h to obtain dry microspheres.

[0082] 6.0g polypropylene glycol and 0.16g 2,2-dihydroxymethyl propionic acid were vacuum dried at 120℃ for 2h. In a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.01g hexamethylene diisocyanate and 30μL dibutyltin dilaurate were added to a three-necked flask equipped with a condenser and mixed. The mixture was heated to 80℃ and mechanically stirred for 2h. 2,2-dihydroxymethyl propionic acid was added and the reaction was continued at 80℃ for 2h. The mixture was cooled to 60℃ and 0.25g 2,2'-diaminodiphenyl disulfide was added and the reaction was continued at 60℃ for 2h. The mixture was cooled to 40℃ and 0.18g 2-(4-Aminophenyl)-5-aminobenzimidazole, continue to react at 40°C for 2h; cool to 35°C, add acetone to dilute, and continue to add 0.2ml of triethylamine to react for 0.5h; add 12ml of deionized water, stir at a speed of 3000rpm until completely emulsified, and remove acetone by vacuum distillation to obtain a water-based polyurethane emulsion.

[0083] Microspheres with a solid content of 5 wt% were added to the aqueous polyurethane emulsion and ultrasonically stirred evenly. A deionized water solution of 0.1 mol / L zinc trifluoromethanesulfonate was added dropwise. The ratio of metal salt to imidazole functional group in the reaction system was 1:7. After the addition was completed, magnetic stirring was performed for 12 hours. After sufficient reaction, the mixture was placed in a drying oven at 60°C and dried for 24 hours, and then vacuum dried for 12 hours to obtain a self-healing aqueous polyurethane composite material.

[0084] Example 3

[0085] 5 g of polyvinyl pyrrolidone was ultrasonically dispersed in 100 g of ethanol and added to a three-necked flask and magnetic stirring was started. 3.33 g of isophorone diisocyanate and 4.40 g of pentaerythritol tetrakis(3-mercaptopropionate) were mixed and stirred, then added to the three-necked flask and reacted at room temperature for 2 h. 0.56 g of 1-vinylimidazole was added and the reaction was continued for 12 h. The obtained product was centrifuged and washed 3 times and then freeze-dried for 48 h to obtain dry microspheres.

[0086] 2.0 g of polytetrahydrofuran diol, 0.4 g of polyethylene glycol and 0.16 g of 2,2-dimethylolpropionic acid were vacuum dried at 120° C. for 2 h. Under a nitrogen atmosphere, the dried polytetrahydrofuran diol, polyethylene glycol, 1.33 g of isophorone diisocyanate and 0.03 g of stannous octoate were added to a three-necked flask equipped with a condenser, mixed, heated to 80° C., and mechanically stirred for 2 h. 2,2-dimethylolbutyric acid was added, and the reaction was continued at 80° C. for 2 h. The temperature was lowered to 60°C, 0.25 g of 3,3'-dihydroxydiphenyl disulfide was added, and the reaction was continued at 60°C for 2 h; the temperature was lowered to 40°C, 0.18 g of 2-(4-aminophenyl)-5-aminobenzimidazole was added, and the reaction was continued at 40°C for 2 h; the temperature was lowered to 35°C, acetone was added for dilution, and 0.2 ml of triethylamine was added for 0.5 h; 12 ml of deionized water was added, and the mixture was stirred at a speed of 3000 rpm until it was completely emulsified, and the acetone was removed by vacuum distillation to obtain a waterborne polyurethane emulsion;

[0087] Microspheres with a solid content of 10 wt% were added to the aqueous polyurethane emulsion and ultrasonically stirred evenly. A deionized water solution of 0.1 mol / L ferric chloride was added dropwise. The ratio of metal salt to imidazole functional group in the reaction system was 1:4. After the addition was completed, magnetic stirring was performed for 12 hours. After sufficient reaction, the mixture was placed in a drying oven at 60°C and dried for 24 hours, and then vacuum dried for 12 hours to obtain a self-healing waterborne polyurethane composite material.

[0088] Example 4

[0089] 5 g of polyvinyl pyrrolidone was ultrasonically dispersed in 100 g of ethanol and added to a three-necked flask and magnetic stirring was started. 2.52 g of 1,6-hexamethylene diisocyanate and 4.40 g of pentaerythritol tetrakis(3-mercaptopropionic acid) were mixed and stirred, then added to the three-necked flask and reacted at room temperature for 2 h. 0.56 g of 1-vinylimidazole was added and the reaction was continued for 12 h. The obtained product was centrifuged and washed 3 times and then freeze-dried for 48 h to obtain dry microspheres.

[0090] 3.0g of polytetrahydrofuran diol and 0.16g of 2,2-dihydroxymethyl propionic acid were vacuum dried at 120°C for 2h. In a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.57g of 4,4'-diisocyanate dicyclohexylmethane and 0.03g of bismuth isooctanoate were added to a three-necked flask equipped with a condenser and mixed. The mixture was heated to 80°C and mechanically stirred for 2h. 2,2-dihydroxymethyl propionic acid was added and the reaction was continued at 80°C for 2h. The mixture was cooled to 60°C and 0.25g of 4,4'-diaminodiphenyl disulfide was added and the reaction was continued at 60°C for 2h. The mixture was cooled to 40°C and 0.18g of 2-(4-aminophenyl)-5-aminobenzimidazole, continue to react at 40°C for 2h; cool to 35°C, add acetone to the reaction system obtained in step (4) in a nitrogen atmosphere to dilute, and then continue to add 0.2ml of triethylamine to react for 0.5h; add 12ml of deionized water, stir at a speed of 3000rpm until completely emulsified, and remove acetone by vacuum distillation to obtain an aqueous polyurethane emulsion;

[0091] Microspheres with a solid content of 25 wt% were added to the aqueous polyurethane emulsion and ultrasonically stirred evenly. A deionized water solution of 0.1 mol / L ferric chloride was added dropwise. The ratio of metal salt to imidazole functional group in the reaction system was 1:4. After the addition was completed, magnetic stirring was performed for 12 hours. After sufficient reaction, the mixture was placed in a drying oven at 60°C and dried for 24 hours, and then further vacuum dried for 12 hours to obtain a self-healing waterborne polyurethane composite material.

[0092] Example 5

[0093] 5 g of polyvinyl pyrrolidone was ultrasonically dispersed in 100 g of ethanol and then added to a three-necked flask and magnetic stirring was started. 2.52 g of 1,6-hexamethylene diisocyanate and 4.40 g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester were mixed and stirred, and then added to the three-necked flask to react at room temperature for 2 h. 0.56 g of 1-vinyl imidazole was added and the reaction was continued for 12 h. The obtained product was centrifuged and washed 3 times and then freeze-dried for 48 h to obtain dry microspheres.

[0094] 3.0g of polytetrahydrofuran diol and 0.16g of 2,2-dimethylol propionic acid were vacuum dried at 120°C for 2h. In a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.50g of 4,4'-diphenylmethane diisocyanate and 0.03g of bismuth isooctanoate were added to a three-necked flask equipped with a condenser, and the mixture was heated to 80°C and mechanically stirred for 2h. 2,2-dimethylol propionic acid was added and the reaction was continued at 80°C for 2h. 0.25g of 4,4'-dihydroxydiphenyl disulfide was added and the reaction was continued at 60°C for 2h. 0.18g of 2-(4-aminophenyl)-5-aminobenzimidazole, continue to react at 40°C for 2h; add acetone to dilute, and continue to add 0.2ml triethylamine to react for 0.5h; add 12ml deionized water, stir at a speed of 3000rpm until completely emulsified, and remove acetone by vacuum distillation to obtain a waterborne polyurethane emulsion;

[0095] Microspheres with a solid content of 30 wt% were added to the aqueous polyurethane emulsion and ultrasonically stirred evenly. A deionized water solution of 0.1 mol / L ferric chloride was added dropwise. The ratio of metal salt to imidazole functional group in the reaction system was 1:4. After the addition was completed, magnetic stirring was performed for 12 hours. After sufficient reaction, the mixture was placed in a drying oven at 60°C and dried for 24 hours, and then further vacuum dried for 12 hours to obtain a self-healing waterborne polyurethane composite material.

[0096] Comparative Example

[0097] 3.0g of polytetrahydrofuran diol and 0.16g of 2,2-dihydroxymethyl propionic acid were vacuum dried at 120℃ for 2h. In a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.33g of isophorone diisocyanate, and 30μL of dibutyltin dilaurate were added to a three-necked flask equipped with a condenser, mixed, heated to 80℃, and mechanically stirred for 2h; 2,2-dihydroxymethyl propionic acid was added, and the reaction continued at 80℃ for 2h. 0.25g of 4,4'-diaminodiphenyl disulfide was added, and the reaction continued at 60℃ for 2h. The temperature was lowered to 40℃, and 0.18g of 2-(4-aminophenyl)-5-aminobenzimidazole was added, and the reaction continued at 40℃ for 2h. The mixture was cooled to 35°C, diluted with acetone, and then 0.2 ml of triethylamine was added to react for 0.5 h. 12 ml of deionized water was added and stirred at 3000 rpm until completely emulsified. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane emulsion. The emulsion was dried in a drying oven at 60°C for 24 h and then further vacuum dried for 12 h to obtain a self-healing aqueous polyurethane elastomer.

[0098] In order to illustrate the relevant properties of the elastomer provided by the present invention, corresponding descriptions are given in conjunction with the accompanying drawings.

[0099] Figure 1It is the stress-strain curve obtained by mechanical property test of the elastomer prepared in Example 1, wherein WPU is a waterborne polyurethane matrix, WPU+2wt% corresponds to the curve measured by the elastomer prepared in Example 1, the amount of microspheres added is 2wt%, and the ratio of metal salt to amino-containing imidazole monomer is 1:4. From the test results, it can be seen that after adding 2wt% of microspheres and metal ions, the strength and toughness of the elastomer are enhanced at the same time. This is because a well-bonded interface is formed between the microspheres and the matrix through metal coordination bonds, so that the external stress can be effectively transferred from the matrix to the microspheres, thereby improving the bearing capacity of the material. At the same time, the dissociation and reorganization of the metal coordination bonds can further improve the ability of the elastomer to dissipate energy, thereby improving the toughness of the material.

[0100] Figure 2 The DSC curve of the self-repairing waterborne polyurethane elastomer based on the dynamic interface and its corresponding proportion in Example 1, wherein WPU is the waterborne polyurethane matrix, WPU+2wt% corresponds to the curve measured by the elastomer prepared in Example 1, the amount of microspheres added is 2wt%, and the ratio of metal salt to amino-containing imidazole monomer is 1:4. Figure 2 It can be seen that after adding microspheres and metal ions, the glass transition temperature Tg of the obtained elastomer is significantly improved relative to the matrix. This is because the added metal ions form metal coordination bonds with the imidazole in the matrix and microspheres, acting as chemical cross-linking points, increasing the cross-linking density of the system, thereby further restricting the movement of the molecular chains, thereby increasing the glass transition temperature of the obtained elastomer.

[0101] Figure 3 This is a microscope image of artificial scratches on the surface of the self-repairing waterborne polyurethane elastomer based on the dynamic interface reinforcement and toughening of Example 1 repaired at 80°C for 0h (before repair) and 5h (after repair for 5h), with a magnification of 25. Figure 3 It can be seen that the scratches on the prepared elastomer basically disappeared after being repaired at 80°C for 5 hours. This is because the disulfide bond contained in the prepared elastomer is a relatively weak covalent bond with high dynamic reversibility. Under the repair condition of 80°C, the disulfide bond can be easily broken and reformed, thus giving the elastomer a high self-healing efficiency. At the same time, the breaking and reorganization of the imidazole-metal ion coordination bond formed between the microspheres and the matrix can also enhance the self-healing performance of the elastomer to a certain extent.

[0102] The present invention provides a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening and a preparation method thereof: firstly, isocyanate-functionalized microspheres are obtained by dispersion polymerization, and then reacted with amino-containing imidazole monomers to obtain imidazole-functionalized high-elasticity and high-modulus microspheres; the structure of the waterborne polyurethane is designed, and a chain extender containing disulfide bonds and imidazole is gradually introduced to obtain an imidazole-functionalized waterborne polyurethane matrix with self-repairing ability; after the microspheres are composited with the matrix, metal ions are added to produce a coordination effect, so that a dynamic interface is formed between the microspheres and the matrix. On the one hand, the high-elasticity and high-modulus microspheres can improve the strength of the elastomer as reinforcing fillers; on the other hand, the metal / imidazole coordination effect enhances the interfacial bonding force between the microspheres and the matrix, increases the crosslinking density of the system, and thus improves the strength of the elastomer. In addition, the metal / imidazole coordination bond has dynamic reversibility, can break-reorganize during the stretching process, dissipates a large amount of energy, and further improves the toughness and self-repairing performance of the elastomer. The present invention utilizes the high elasticity and high modulus properties of the microspheres and the dynamic interface formed with the waterborne polyurethane matrix to jointly improve the mechanical properties and self-healing properties of the elastomer, solving the contradictory problem that the strength-toughness and strength-self-healing properties of the material cannot be improved synergistically.

[0103] The above embodiments are only some embodiments listed for facilitating understanding of the synthesis and application methods of the materials of the present invention, and are not intended to limit the present invention. It is understood that relevant practitioners can easily make appropriate modifications to this structure, so any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, characterized in that: The following steps are involved: preparing a waterborne polyurethane emulsion; The polyvinyl pyrrolidone is uniformly dispersed in an ethanol solution, a multifunctional thiol and a multifunctional isocyanate are added, and after reacting for 2 to 4 hours, an amino-containing imidazole monomer is added, and the reaction is continued for 12 hours or more to obtain a microsphere powder; The microsphere powder is uniformly dispersed in an aqueous polyurethane emulsion, a metal salt solution is added, and then the water is volatilized to form a membrane material, thereby obtaining a self-repairing aqueous polyurethane composite elastomer based on dynamic interface reinforcement and toughening; Wherein, the metal salt is one or more of 4-fluorophenylmagnesium chloride, 1,3-dioxolane-2-ethylmagnesium bromide, bis(trifluoromethanesulfonyl)imide zinc, 2-mercaptobenzothiazole zinc salt, zinc trifluoromethanesulfonate, zinc acetate, and ferric chloride.

2. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 1, characterized in that: The mass proportion of the microsphere powder in the reaction system is 1wt% to 30wt%; the molar ratio of the metal salt to the amino-containing imidazole monomer is 1:4-7.

3. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 1, characterized in that: The multifunctional thiol is one of trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), tetrakis(3-mercaptopropionate) pentaerythritol ester, and tetrakis(3-mercaptobutyrate) pentaerythritol ester, and its structural formula is as follows:

4. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 1, characterized in that: The multifunctional isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate, and its structural formula is as follows: The isocyanate functional groups are in excess of 10-30% relative to the mercapto functional groups.

5. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 1, characterized in that: The amino-containing imidazole monomer is one or more of 2-(2-methyl-1H-imidazol-1-yl)ethylamine, 1-(3-amino-propyl)imidazole, 2-(1H-imidazol-1-yl)ethylamine, 4-(2-methyl-1H-imidazole)benzylamine, and 1H-imidazole-2-methylamine, and the structural formula thereof is as follows:

6. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 1, characterized in that: The aqueous polyurethane emulsion is prepared according to the following steps: After mixing diisocyanate, polyether polyol and catalyst, adding organic solvent, heating to 70-80°C for reaction for 1-4h, adding carboxylic acid hydrophilic chain extender for reaction for 2-3h, then adding small molecule chain extender containing disulfide bond for reaction for 2-3h, then cooling to 40-50°C, adding small molecule amine chain extender containing imidazole group for reaction for 3-4h, cooling to 30-35°C, adding organic solvent for dilution, then adding neutralizer for reaction for 0.5-1h, then adding water solvent for stirring and emulsification to obtain the primary product; The organic solvent is removed by distillation under reduced pressure from the initial product to obtain an aqueous polyurethane emulsion; The catalyst is one of dibutyltin dilaurate, stannous octoate and bismuth isooctanoate.

7. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 6, characterized in that: The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate; The polyether polyol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol; The organic solvent is one or more of acetone, N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone.

8. The method for preparing a self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening according to claim 6, characterized in that: The carboxylic acid hydrophilic chain extender is dimethylol propionic acid and / or dimethylol butyric acid; The small molecule chain extender containing a disulfide bond is a small molecule alcohol chain extender containing a disulfide bond or a small molecule amine chain extender containing a disulfide bond; The small molecule amine chain extender containing imidazole groups is one or more of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,2-diaminoimidazole, and 4-amino-5-imidazolecarboxamide; The neutralizing agent is one or more of triethylamine, N,N-dimethylethanolamine, diethanolamine and triethanolamine.

9. A self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening obtained by the method described in any one of claims 1 to 8.

10. Use of the self-repairing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening as claimed in claim 9 in the field of self-repairing polymer materials.

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