Self-healing waterborne polyurethane composite elastomers based on dynamic interface reinforcement and toughening, their preparation methods and applications

Abstract

This invention relates to a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, its preparation method, and its application, belonging to the field of self-healing polymer materials technology. The method includes preparing a waterborne polyurethane emulsion; uniformly dispersing polyvinylpyrrolidone in an ethanol solution, adding a multifunctional thiol and a multifunctional isocyanate, and adding an amino-containing imidazole monomer to obtain microsphere powder; uniformly dispersing the microsphere powder in the waterborne polyurethane emulsion, adding a metal salt solution, and then evaporating the water to form a film material, thus obtaining the self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening. This invention, through designing the structure of the waterborne polyurethane, modifying the surface of the microspheres, and introducing a dynamic interface composite, yields a self-healing waterborne polyurethane elastomer with excellent comprehensive performance, simultaneously improving the elastomer's strength, toughness, and self-healing ability.

Description

Technical Field

[0001] This invention belongs to the field of self-healing polymer materials technology, specifically relating to a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, its preparation method, and its application. Background Technology

[0002] Imparting self-healing capabilities to polymer materials can indeed significantly improve their service life, safety, and stability. However, there is a trade-off between the mechanical strength and self-healing properties of self-healing polymers. For example, materials with strong chemical bonds often have high mechanical strength, but due to the dynamic nature of chemical bonds and poor chain flowability, they are difficult to self-heal. Conversely, materials based on weaker chemical bonds can achieve self-healing, but their mechanical properties are usually lower because the breaking of weak sacrificial bonds requires less energy, making the material more susceptible to deformation under external forces, thus reducing its mechanical strength. Therefore, achieving a balance between the two is crucial.

[0003] In practical applications, materials typically require comprehensive properties, such as high mechanical strength, good electrical conductivity, mild repair conditions, environmental tolerance, and synergistic repair of electrical and mechanical properties. Therefore, designing and synthesizing materials that combine high mechanical strength with excellent self-healing properties is a challenging problem. To overcome this challenge, researchers have proposed various strategies to enhance the mechanical strength of self-healing polymers. For example, by introducing dynamic cross-linking structures or supramolecular interactions, rapid post-damage remodeling can be achieved without sacrificing mechanical strength; aromatic disulfide-induced self-reinforced polyurethane elastomers can achieve self-healing properties while maintaining high tensile strength and toughness; hierarchical hydrogen bonding interactions and metal coordination can enhance the mechanical strength of self-healing elastomers; adding fillers to elastomers can improve their elastic modulus and fracture toughness. These methods demonstrate the possibility of simultaneously improving mechanical strength and self-healing capabilities through the rational design of molecular structures and interaction forces. In summary, resolving 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, thereby meeting the needs of engineering applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention primarily resolves the contradictory problem of the inability to synergistically improve the strength, toughness, and self-healing properties of elastomer materials. This invention provides a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, its preparation method, and its applications. By designing the structure of waterborne polyurethane, modifying the surface of microspheres, and introducing a dynamic interface for composite formation, this invention yields a self-healing waterborne polyurethane elastomer with excellent comprehensive performance, simultaneously improving the elastomer's strength, toughness, and self-healing ability.

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

[0006] Preparation of aqueous polyurethane emulsions;

[0007] Polyvinylpyrrolidone was uniformly dispersed in an ethanol solution, and polyfunctional thiols and polyfunctional isocyanates were added. After reacting for 2-4 hours, amino-containing imidazole monomers were added, and the reaction was continued for 12 hours or more to obtain microsphere powder.

[0008] Microsphere powder is uniformly dispersed in an aqueous polyurethane emulsion, a metal salt solution is added, and then the water is evaporated to form a film material, thus obtaining a self-healing aqueous polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

[0009] The metal salt is one or more of the following: 4-fluorophenyl magnesium chloride, 1,3-dioxocyclopentyl-2-ethyl magnesium bromide, zinc bis(trifluoromethanesulfonyl)imide, zinc 2-mercaptobenzothiazole, zinc trifluoromethanesulfonate, zinc acetate, and ferric chloride.

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

[0011] Preferably, the polyfunctional thiol is one of trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tetrakis(3-mercaptopropionate), and pentaerythritol tetrakis(3-mercaptobutyrate), with the following structural formula:

[0012]

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

[0014]

[0015] The isocyanate functional group is in excess of the mercapto functional group by 10-30%.

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

[0017]

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

[0019] After mixing diisocyanate, polyether polyol and catalyst, an organic solvent is added, and the mixture is heated to 70-80℃ and reacted for 1-4 hours. Then, a carboxylic acid hydrophilic chain extender is added and the reaction continues for 2-3 hours. Next, a small molecule chain extender containing disulfide bonds is added and the reaction continues for 2-3 hours. Then, the temperature is lowered to 40-50℃, and a small molecule amine chain extender containing imidazole groups is added and the reaction continues for 3-4 hours. After the temperature is lowered to 30-35℃, an organic solvent is added for dilution, and then a neutralizing agent is added and the reaction continues for 0.5-1 hours. Finally, an aqueous solvent is added and the mixture is stirred and emulsified to obtain the initial product.

[0020] The organic solvent was removed from the initial product by vacuum distillation 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 selected from 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 glycol;

[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 dimethylolpropionic acid and / or dimethylolbutyric acid;

[0026] The small molecule chain extender containing disulfide bonds is a small molecule alcohol chain extender containing disulfide bonds or a small molecule amine chain extender containing disulfide bonds.

[0027] The small molecule amine chain extender containing an imidazole group is one or more of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,2-diaminoimidazole, and 4-amino-5-imidazolium carboxamide.

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

[0029] The second objective of this invention is to provide a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

[0030] The third objective of this invention is to provide an application of a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening in the field of self-healing polymer materials.

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

[0032] This invention provides a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, its preparation method, and its application. This invention utilizes high-elasticity, high-modulus microspheres to design the structure of waterborne polyurethane, introducing a small-molecule chain extender containing imidazole to obtain an imidazole-functionalized waterborne polyurethane matrix. By adding metal ions, the imidazole-functionalized microspheres and the imidazole-functionalized matrix are composited. The coordination crosslinking effect of imidazole / metal and the high elasticity and high modulus properties of the microspheres further enhance the strength of the matrix.

[0033] This invention modifies the surface of microspheres to create a dynamic interface between the microspheres and the matrix through imidazole-metal coordination, thereby establishing an efficient stress transfer and energy dissipation mechanism, improving the energy dissipation capacity of the material during tensile processes, and further enhancing the toughness of the material.

[0034] This invention designs the structure of waterborne polyurethane to introduce dynamic disulfide bonds, giving 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, the material's repair capability can be further enhanced through the breaking and recombination of dynamic bonds when the material is damaged.

[0035] Compared with directly adding microspheres, the formation of dynamic interfaces in this invention can significantly improve the dispersion and compatibility of microspheres in the matrix, significantly improve the interfacial bonding between the two phases, enhance the interfacial stress transfer effect, effectively inhibit crack propagation, and thus improve the overall performance of the material. Attached Figure Description

[0036] Figure 1 This is a stress-strain curve of a self-healing waterborne polyurethane elastomer and its waterborne polyurethane matrix, which is based on a dynamic interface and is reinforced and toughened. The amount of microspheres added is 2wt%, and the ratio of metal salt to amino-containing imidazole monomer is 1:4.

[0037] Figure 2 The data are DSC curves of a self-healing waterborne polyurethane elastomer and its waterborne polyurethane matrix based on a dynamic interface-enhanced and toughened structure, wherein the amount of microspheres added is 2wt%, and the ratio of metal salt to amino-containing imidazole monomer is 1:4.

[0038] Figure 3 These are microscopic images of artificial scratches on the surface of a self-healing waterborne polyurethane elastomer based on a dynamic interface, after repair at 80℃ for 0 hours and 5 hours, with a magnification of 25. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. However, it should be understood that the listed embodiments are only for the purpose of understanding the core methods and application fields of the present invention, but the scope of the present invention is not limited thereto.

[0040] The purpose of this invention is to provide a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, its preparation method, and its application. This invention mainly utilizes the high elasticity and high modulus of 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 of the inability to synergistically improve material strength and toughness, and strength and self-healing properties.

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

[0042] Preparation of aqueous polyurethane emulsions;

[0043] Polyvinylpyrrolidone was uniformly dispersed in an ethanol solution, and polyfunctional thiols and polyfunctional isocyanates were added. After reacting for 2-4 hours, amino-containing imidazole monomers were added, and the reaction was continued for 12 hours or more to obtain microsphere powder.

[0044] Microsphere powder is uniformly dispersed in an aqueous polyurethane emulsion, a metal salt solution is added, and then the water is evaporated to form a film material, thus obtaining a self-healing aqueous polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

[0045] The metal salt is one or more of the following: 4-fluorophenyl magnesium chloride, 1,3-dioxocyclopentyl-2-ethyl magnesium bromide, zinc bis(trifluoromethanesulfonyl)imide, zinc 2-mercaptobenzothiazole, zinc trifluoromethanesulfonate, zinc acetate, and ferric chloride.

[0046] The microsphere powder prepared in this invention is an imidazole-functionalized high-elasticity, high-modulus microsphere. This invention utilizes imidazole-functionalized high-elasticity, 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, resulting in a reinforced and toughened self-healing elastomer. Specifically, the process includes: first, obtaining isocyanate-functionalized microspheres through dispersion polymerization, then reacting them with amino-containing imidazole monomers to obtain imidazole-functionalized high-elasticity, high-modulus microspheres; designing the structure of the aqueous polyurethane, gradually introducing chain extenders containing disulfide bonds and imidazole, to obtain an imidazole-functionalized aqueous polyurethane matrix with self-healing capabilities; and then adding metal ions after compositing the microspheres with the matrix to generate coordination, forming a dynamic interface between the microspheres and the matrix. On one hand, the high-elasticity, high-modulus microspheres, as reinforcing fillers, can improve the strength of the elastomer; on the other hand, the metal / imidazole coordination 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. Furthermore, the metal / imidazolium coordination bonds exhibit dynamic reversibility, capable of breaking and reforming during stretching, dissipating a significant amount of energy and further enhancing the toughness and self-healing properties of the elastomer. This invention utilizes the high elasticity and modulus 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, resolving the contradictory problem of the inability to synergistically improve material strength and toughness, and strength and self-healing properties.

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

[0048] The polyfunctional thiol is one of trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tetrakis(3-mercaptopropionate), and pentaerythritol tetrakis(3-mercaptobutyrate), with the following structural formula:

[0049]

[0050] The multifunctional isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate, with the following structural formula:

[0051]

[0052] The isocyanate functional group is in excess of the mercapto functional group by 10-30%.

[0053] The amino-containing imidazole monomer is one or more of 2-(2-methyl-1H-imidazol-1-yl)ethylamine, 1-(3-amino-propyl)imidazolium, 2-(1H-imidazol-1-yl)ethylamine, 4-(2-methyl-1H-imidazolium)benzylamine, and 1H-imidazol-2-methylamine, and its structural formula 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, an organic solvent is added, and the mixture is heated to 70-80℃ and reacted for 1-4 hours. Then, a carboxylic acid hydrophilic chain extender is added and the reaction continues for 2-3 hours. Next, a small molecule chain extender containing disulfide bonds is added and the reaction continues for 2-3 hours. Then, the temperature is lowered to 40-50℃, and a small molecule amine chain extender containing imidazole groups is added and the reaction continues for 3-4 hours. After the temperature is lowered to 30-35℃, an organic solvent is added for dilution, and then a neutralizing agent is added and the reaction continues for 0.5-1 hours. Finally, an aqueous solvent is added and the mixture is stirred and emulsified to obtain the initial product.

[0057] The organic solvent was removed from the initial product by vacuum distillation 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 glycol;

[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 dimethylolpropionic acid and / or dimethylolbutyric acid;

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

[0064]

[0065] The imidazole-containing small molecule amine chain extender is one or more of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,2-diaminoimidazole, and 4-amino-5-imidazolium carboxamide, with the following structural formula:

[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 reinforced and toughened self-healing aqueous polyurethane elastomer based on a dynamic interface includes imidazole-functionalized high-elasticity and high-modulus microspheres, an aqueous polyurethane containing imidazole functional groups and dynamically reversible disulfide bonds, and a metal salt. The imidazole-functionalized high-elasticity and high-modulus microspheres form a dynamic interface with the aqueous polyurethane containing imidazole functional groups and dynamically reversible disulfide bonds through imidazole-metal coordination, thereby obtaining a reinforced and toughened self-healing elastomer. The specific preparation steps are as follows:

[0069] Step 1: Preparation of imidazole-functionalized high-elasticity, high-modulus microspheres: Polyvinylpyrrolidone was ultrasonically dispersed in an ethanol solution and transferred to a three-necked flask. Magnetic stirring was started. A mixture of polyfunctional thiols and polyfunctional isocyanates was added to the three-necked flask and reacted for 2 hours, with the isocyanate functional groups in 10-30% excess relative to the thiol functional groups. Amino-containing imidazole monomers were then added and reacted for at least 12 hours. The resulting product was centrifuged and washed multiple times, then freeze-dried for 48 hours to obtain dried microsphere powder.

[0070] Step 2: Preparation of self-healing waterborne polyurethane emulsion: Diisocyanate, polyether polyol and catalyst are mixed and added to a three-necked flask with a small amount of organic solvent. The mixture is heated to 70-80℃ and reacted for 2 hours to obtain an isocyanate-terminated prepolymer. The catalyst used is any one of dibutyltin dilaurate, stannous octoate, or bismuth isooctanoate. The organic solvent is any one of acetone, N,N-dimethylformamide, tetrahydrofuran, or N-methylpyrrolidone. Then, a carboxylic acid hydrophilic chain extender is added and the reaction continues for 2-3 hours. Next, a small molecule alcohol or amine chain extender containing disulfide bonds is added and the reaction continues for 2-3 hours. The temperature is lowered to 40-50℃, and a small molecule amine chain extender containing imidazole groups is added and the reaction continues for 3-4 hours. The temperature is lowered to 30-35℃, acetone is added for dilution, a neutralizing agent is added, and the reaction continues for 0.5-1 hours. Deionized water is added and the mixture is emulsified by high-speed stirring to obtain the initial product. The acetone is removed by vacuum distillation to obtain the waterborne polyurethane emulsion.

[0071] Step 3: Preparation of self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening: Microspheres are ultrasonically dispersed in the obtained waterborne polyurethane emulsion. After thorough mixing, a deionized aqueous solution of metal salt is added dropwise. After the addition is complete, the resulting solution is placed in a drying oven to evaporate the water until the membrane material reaches constant weight, thus obtaining the self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening.

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

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

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

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

[0076] Example 1

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

[0078] 3.0 g of polytetrahydrofuran diol and 0.16 g of 2,2-dimethylolpropionic acid were dried under vacuum at 120 °C for 2 h. Under 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 mixed. The mixture was heated to 80 °C and mechanically stirred for 2 h. Then, 2,2-dimethylolpropionic 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 under a nitrogen atmosphere. The reaction was continued at 60 °C for 2 h. The temperature was lowered to 40 °C, and 0.18 g of [a specific ingredient] was added to the reaction system. 2-(4-aminophenyl)-5-aminobenzimidazole was reacted at 40°C for 2 hours; the temperature was lowered to 35°C, and acetone was added to dilute the reaction system. Then, 0.2 ml of triethylamine was added and the reaction was continued for 0.5 hours; 12 ml of deionized water was added, and the mixture was stirred at 3000 rpm until it was completely emulsified. Finally, acetone was removed by vacuum distillation to obtain an aqueous polyurethane emulsion.

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

[0080] Example 2

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

[0082] 6.0 g of polypropylene glycol and 0.16 g of 2,2-dimethylolpropionic acid were dried under vacuum at 120 °C for 2 h. Under a nitrogen atmosphere, the dried polytetrahydrofuran glycol, 1.01 g of hexamethylene diisocyanate, and 30 μL of dibutyltin dilaurate were added to a three-necked flask equipped with a condenser and mixed. The mixture was heated to 80 °C and mechanically stirred for 2 h. 2,2-dimethylolpropionic 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 2,2'-diaminodiphenyl disulfide was added. 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 was reacted at 40°C for 2 hours; the temperature was lowered to 35°C, acetone was added for dilution, and 0.2 ml of triethylamine was added for 0.5 hours; 12 ml of deionized water was added, and the mixture was stirred at 3000 rpm until completely emulsified. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane emulsion.

[0083] Microspheres with a solid content of 5 wt% were added to an aqueous polyurethane emulsion and ultrasonically stirred until homogeneous. A deionized aqueous 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 complete, the mixture was magnetically stirred for 12 h. After the reaction was complete, the mixture was placed in a drying oven and dried at 60 °C for 24 h, followed by vacuum drying for 12 h to obtain a self-healing aqueous polyurethane composite material.

[0084] Example 3

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

[0086] 2.0 g of polytetrahydrofuran diol, 0.4 g of polyethylene glycol, and 0.16 g of 2,2-dimethylolpropionic acid were dried under vacuum 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 and mixed. The mixture was heated to 80 °C and mechanically stirred for 2 h. 2,2-dimethylolbutyric acid was then added, and the reaction was continued at 80 °C for 2 h. The mixture was cooled to 60°C, and 0.25 g of 3,3'-dihydroxydiphenyl disulfide was added. The reaction was continued at 60°C for 2 h. The mixture was then cooled to 40°C, and 0.18 g of 2-(4-aminophenyl)-5-aminobenzimidazole was added. The reaction was continued at 40°C for 2 h. The mixture was then cooled to 35°C, diluted with acetone, and 0.2 ml of triethylamine was added. The reaction was continued for 0.5 h. 12 ml of deionized water was added, and the mixture was stirred at 3000 rpm until completely emulsified. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane emulsion.

[0087] Microspheres with a solid content of 10 wt% were added to an aqueous polyurethane emulsion and ultrasonically stirred until homogeneous. A 0.1 mol / L deionized water solution of 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 complete, the mixture was magnetically stirred for 12 h. After the reaction was complete, the mixture was placed in a drying oven and dried at 60 °C for 24 h, followed by vacuum drying for 12 h to obtain a self-healing aqueous polyurethane composite material.

[0088] Example 4

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

[0090] 3.0 g of polytetrahydrofuran diol and 0.16 g of 2,2-dimethylolpropionic acid were dried under vacuum at 120 °C for 2 h. Under a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.57 g of 4,4'-diisocyanate dicyclohexylmethane, and 0.03 g 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 2 h. 2,2-dimethylolpropionic 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. The reaction was continued at 60 °C for 2 h. The temperature was lowered to 40 °C, and 0.18 g of bismuth is added. 2-(4-aminophenyl)-5-aminobenzimidazole was reacted at 40°C for 2 hours. The temperature was lowered to 35°C, and acetone was added to the reaction system obtained in step (4) under a nitrogen atmosphere for dilution. Then, 0.2 ml of triethylamine was added and reacted for 0.5 hours. 12 ml of deionized water was added, and the mixture was stirred at 3000 rpm until it was completely emulsified. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane emulsion.

[0091] Microspheres with a solid content of 25 wt% were added to an aqueous polyurethane emulsion and ultrasonically stirred until homogeneous. A 0.1 mol / L deionized water solution of 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 complete, the mixture was magnetically stirred for 12 h. After the reaction was complete, the mixture was placed in a drying oven and dried at 60 °C for 24 h, followed by vacuum drying for 12 h to obtain a self-healing aqueous polyurethane composite material.

[0092] Example 5

[0093] 5g of polyvinylpyrrolidone was ultrasonically dispersed in 100g of ethanol and then added to a three-necked flask with magnetic stirring. 2.52g of 1,6-hexamethylene diisocyanate and 4.40g of pentaerythritol tetrakis(3-mercaptopropionic acid) were mixed and stirred, then added to the three-necked flask and reacted at room temperature for 2 hours. 0.56g of 1-vinylimidazole was added, and the reaction continued for 12 hours. The resulting product was centrifuged, washed three times, and freeze-dried for 48 hours to obtain dried microspheres.

[0094] 3.0 g of polytetrahydrofuran diol and 0.16 g of 2,2-dimethylolpropionic acid were dried under vacuum at 120 °C for 2 h. Under a nitrogen atmosphere, the dried polytetrahydrofuran diol, 1.50 g of 4,4'-diphenylmethane diisocyanate, and 0.03 g 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 2 h. 2,2-dimethylolpropionic acid was added, and the reaction was continued at 80 °C for 2 h. 0.25 g of 4,4'-dihydroxydiphenyl disulfide was added, and the reaction was continued at 60 °C for 2 h. 0.18 g of bismuth isooctanoate was added. 2-(4-aminophenyl)-5-aminobenzimidazole was reacted at 40°C for 2 hours; after dilution with acetone, 0.2 ml of triethylamine was added and reacted for 0.5 hours; 12 ml of deionized water was added and stirred at 3000 rpm until completely emulsified; acetone was removed by vacuum distillation to obtain an aqueous polyurethane emulsion.

[0095] Microspheres with a solid content of 30 wt% were added to an aqueous polyurethane emulsion and ultrasonically stirred until homogeneous. A 0.1 mol / L deionized water solution of 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 complete, the mixture was magnetically stirred for 12 h. After the reaction was complete, the mixture was placed in a drying oven and dried at 60 °C for 24 h, followed by vacuum drying for 12 h to obtain a self-healing aqueous polyurethane composite material.

[0096] Comparative Example

[0097] 3.0 g of polytetrahydrofuran diol and 0.16 g of 2,2-dimethylolpropionic acid were dried under vacuum at 120 °C for 2 h. Under 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 mixed. The mixture was heated to 80 °C and mechanically stirred for 2 h. 2,2-dimethylolpropionic acid was added, and the reaction was continued at 80 °C for 2 h. 0.25 g of 4,4'-diaminodiphenyl disulfide was added, and the reaction was continued at 60 °C for 2 h. The mixture was cooled to 40 °C, and 0.18 g of 2-(4-aminophenyl)-5-aminobenzimidazole was added. The reaction was continued at 40 °C for 2 h. The mixture was cooled to 35°C, diluted with acetone, and then 0.2 ml of triethylamine was added and reacted for 0.5 h. 12 ml of deionized water was added, and the mixture was stirred at 3000 rpm until it was 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 dried under vacuum for 12 h to obtain a self-healing aqueous polyurethane elastomer.

[0098] To illustrate the relevant properties of the elastomer provided by the present invention, the description is provided in conjunction with the accompanying drawings.

[0099] Figure 1The figures show the stress-strain curves obtained from mechanical property tests of the elastomer prepared in Example 1. WPU is the waterborne polyurethane matrix, and WPU+2wt% corresponds to the curve measured for 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. The test results show that after adding 2wt% microspheres and metal ions, both the strength and toughness of the elastomer are enhanced. This is because a well-bonded interface is formed between the microspheres and the matrix through metal coordination bonds, allowing applied stress to be effectively transferred from the matrix to the microspheres, thereby improving the material's load-bearing capacity. Simultaneously, the dissociation and recombination of the metal coordination bonds further enhances the elastomer's energy dissipation ability, thus improving the material's toughness.

[0100] Figure 2 This is Example 1, showing the DSC curves of the enhanced and toughened self-healing waterborne polyurethane elastomer based on a dynamic interface and its corresponding proportions. WPU is the waterborne polyurethane matrix, and 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... Figure 2 As can be seen, the glass transition temperature (Tg) of the resulting elastomer is significantly increased relative to that of the matrix after the addition of microspheres and metal ions. This is because the added metal ions form metal coordination bonds with the imidazole in the matrix and microspheres, which act as chemical crosslinking points, increasing the crosslinking density of the system and further restricting the movement of molecular chains, thus increasing the glass transition temperature of the resulting elastomer.

[0101] Figure 3 These are microscopic images (25x magnification) of artificial scratches on the surface of a self-healing waterborne polyurethane elastomer based on a dynamic interface-reinforced and toughened material, repaired at 80°C for 0 hours (before repair) and 5 hours (after repair). Figure 3 It can be seen that the scratches of the prepared elastomer basically disappeared after 5 hours of repair at 80℃. This is because the disulfide bonds contained in the prepared elastomer are relatively weak covalent bonds with high dynamic reversibility. Under the repair conditions of 80℃, the disulfide bonds can easily break and reform, thus endowing the elastomer with high self-healing efficiency. At the same time, the breaking and recombination of the imidazole-metal ion coordination bonds formed between the microspheres and the matrix can also enhance the self-healing performance of the elastomer to a certain extent.

[0102] This invention provides a self-healing waterborne polyurethane composite elastomer based on dynamic interface reinforcement and toughening, and its preparation method: First, isocyanate-functionalized microspheres are obtained through dispersion polymerization, and then reacted with amino-containing imidazole monomers to obtain imidazole-functionalized high-elasticity, high-modulus microspheres. The structure of the waterborne polyurethane is designed, and chain extenders containing disulfide bonds and imidazole are gradually introduced to obtain an imidazole-functionalized waterborne polyurethane matrix with self-healing capabilities. After the microspheres and matrix are composited, metal ions are added to generate coordination, forming a dynamic interface between the microspheres and the matrix. On the one hand, the high-elasticity, high-modulus microspheres, as reinforcing fillers, can improve the strength of the elastomer; on the other hand, the metal / imidazole coordination 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, and can break and recombine during stretching, dissipating a large amount of energy, further improving the toughness and self-healing performance of the elastomer. This invention utilizes the high elasticity and high modulus of microspheres and the dynamic interface formed with the waterborne polyurethane matrix to jointly improve the mechanical properties and self-healing properties of the elastomer, thus solving the contradictory problem that the material strength-toughness and strength-self-healing properties cannot be improved in a coordinated manner.

[0103] The above embodiments are merely some examples listed to facilitate 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 those skilled in the art can easily make appropriate modifications to this structure; therefore, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for the preparation of a dynamically interphase enhanced toughened self-repairing waterborne polyurethane hybrid elastomer, characterized in that, comprising the following steps: preparing an aqueous polyurethane emulsion; dispersing polyvinylpyrrolidone in an ethanol solution, adding a multifunctional thiol and a multifunctional isocyanate, after 2-4 hours of reaction, adding 1-vinylimidazole, continuing to react for 12 hours or more, to obtain a microsphere powder; dispersing the microsphere powder in the aqueous polyurethane emulsion, adding a metal salt solution, and then evaporating water to form a film material, to obtain a dynamic interface reinforced and toughened self-repairing aqueous polyurethane composite elastomer; wherein the metal salt is one or more of 4-fluorophenyl magnesium chloride, 1,3-dioxolane-2-ethyl magnesium bromide, bis(trifluoromethylsulfonyl) imidazole zinc, 2-mercaptobenzothiazole zinc salt, zinc trifluoromethane sulfonate, zinc acetate, and iron chloride; the multifunctional thiol is one of trimethylolpropane tri(3-mercaptopropionate), trimethylolpropane tri(3-mercaptobutyrate), pentaerythritol tetra(3-mercaptopropionate), and pentaerythritol tetra(3-mercaptobutyrate); the multifunctional isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexyl methane, 4,4'-diphenyl methane diisocyanate, and toluene diisocyanate; the aqueous polyurethane emulsion is prepared according to the following steps: mixing diisocyanate, polyether polyol, and catalyst, adding an organic solvent, heating to 70-80°C for 1-4 hours, adding a carboxylic acid hydrophilic chain extender for 2-3 hours, then adding a small molecule chain extender containing a disulfide bond for 2-3 hours, then cooling to 40-50°C, adding a small molecule amine chain extender containing an imidazole group for 2 hours, then cooling to 30-35°C, adding an organic solvent for dilution, then adding a neutralizing agent for 0.5-1 hours, and then adding an aqueous solvent to emulsify to obtain a primary product; distilling the primary product under reduced pressure to remove the organic solvent, to obtain the aqueous polyurethane emulsion; the catalyst is one of dibutyltin dilaurate, stannous octoate, and bismuth isooctoate; the mass ratio of the microsphere powder in the reaction system is 1 wt%-30 wt%, and the molar ratio of the metal salt to 1-vinylimidazole is 1:4-7.

2. The preparation method of the dynamic interface reinforced and toughened self-repairing aqueous polyurethane composite elastomer according to claim 1, characterized in that: the diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexyl methane, 4,4'-diphenyl methane 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-methyl pyrrolidone.

3. The preparation method of the dynamic interface reinforced and toughened self-repairing aqueous polyurethane composite elastomer according to claim 1, characterized in that: the carboxylic acid hydrophilic chain extender is dimethylolpropionic acid and / or dimethylolbutyric acid. The small-molecule chain extender containing disulfide bond is a small-molecule alcohol chain extender containing disulfide bond or a small-molecule amine chain extender containing disulfide bond; The small-molecule amine chain extender containing imidazole group is one or more of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,2-diaminoimidazole, and 4-amino-5-imidazole formamide; The neutralizing agent is one or more of triethylamine, N,N-dimethylethanolamine, diethanolamine, and triethanolamine.

4. A self-repairing waterborne polyurethane composite elastomer based on dynamic interfacial reinforcement and toughening, which is prepared by the method according to any one of claims 1 to 3.

5. Application of the self-repairing waterborne polyurethane composite elastomer based on dynamic interfacial reinforcement and toughening according to claim 4 in the field of self-repairing polymer materials.

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