A dual microcapsule self-repairing waterborne polyurethane material and a preparation method thereof

Abstract

The application belongs to the technical field of self-repairing materials, and particularly relates to a kind of double-microcapsule self-repairing water-based polyurethane material and its preparation method. It comprises: ultrasonic dispersion of cellulose nanocrystals in deionized water to form an aqueous phase, adding dry oil and sodium dodecyl sulfate, and stirring to obtain a dry oil microcapsule with a Pickering emulsion as a template. Then, polyvinylpyrrolidone aqueous solution, non-polar solvent solution of thiophene monomer and ammonium persulfate aqueous solution are prepared. The first two are mixed and ultrasonically dispersed, then mixed with the ammonium persulfate aqueous solution and stirred to polymerize. After the reaction is completed, polythiophene microcapsule suspension is obtained. After centrifugation, the supernatant is colorless. The solid is washed and dried to obtain polythiophene microcapsules. Finally, the two kinds of microcapsules are added to the water-based polyurethane, mixed uniformly, dried at room temperature to form a double-microcapsule self-repairing water-based polyurethane material. The application realizes the self-repairing and mechanical property improvement of the double-microcapsule self-repairing water-based polyurethane material under room temperature natural light.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of self-repairing materials, and particularly relates to a double-microcapsule self-repairing waterborne polyurethane material and a preparation method thereof. BACKGROUND

[0002] Self-repairing materials have attracted considerable attention due to their ability to actively repair damaged parts to restore the original function, and are widely used in aerospace, automotive industry, artificial electronic skin, wearable electronic devices and other fields. White et al. (Nature, 2001, 409: 794-797) first designed a microcapsule self-repairing material system, which can embed microcapsules that can break when the matrix material cracks, release repair liquid through siphon effect, fill the crack damage part, and then solidify through cross-linking to repair the matrix material. In the field of polymer self-repairing materials, waterborne polyurethane (WPU) system is gradually becoming an extremely attractive matrix selection due to its unique advantages. Waterborne polyurethane uses water as a dispersion medium, which significantly reduces the emission of volatile organic compounds (VOC), and at the same time endows the material with better flexibility, elasticity and biocompatibility. However, the traditional single-component microcapsule self-repairing system still has some limitations, such as dependence of repair rate on external conditions (such as heating, ultraviolet light, etc.), insufficient repair efficiency, limited mechanical property recovery after repair, etc.

[0003] In particular, for room temperature self-repairing systems, there are challenges such as slow curing speed and harsh catalytic conditions. Although some researches have tried to add catalysts or photosensitizers to improve the repair efficiency, it is still difficult to achieve fast and efficient self-repairing under natural light and room temperature conditions, and most of the catalytic systems have poor compatibility with water environment, which limits their practical application. SUMMARY

[0004] To solve the problems in the prior art, the application provides a double-microcapsule self-repairing waterborne polyurethane material and a preparation method thereof. The method constructs dry oil repair microcapsules and polythiophene catalysis-enhanced microcapsules through Pickering emulsion and interfacial polymerization technology, respectively, and the two work together to provide an efficient, convenient and environmentally friendly self-repairing solution for waterborne materials.

[0005] To achieve the above purpose, the application adopts the following technical solutions:

[0006] In a first aspect, the application provides a preparation method of a double-microcapsule self-repairing waterborne polyurethane material, comprising the following steps:

[0007] The cellulose nanocrystal is ultrasonically dispersed in deionized water to form an aqueous phase; dry oil and sodium dodecyl sulfate are added to the aqueous phase, and after stirring, dry oil microcapsules are obtained;

[0008] Polyvinylpyrrolidone is dissolved in deionized water to obtain solution A; a thiophene monomer is dissolved in a non-polar solvent to obtain solution B; ammonium persulfate is dissolved in deionized water to obtain solution C; the solution A and the solution B are mixed and ultrasonically dispersed to obtain solution D; the solution C and the solution D are mixed and stirred to perform a polymerization reaction, and after the polymerization reaction is completed, a polythiophene microcapsule suspension is obtained; the polythiophene microcapsule suspension is centrifuged until the supernatant is colorless, and the precipitated solid is washed, vacuum dried to obtain polythiophene microcapsules;

[0009] The dry oil microcapsules and the polythiophene microcapsules are added to the aqueous polyurethane, mixed uniformly, dried at room temperature to form the double-microcapsule self-repairing aqueous polyurethane material.

[0010] Preferably, the molar concentration of the polyvinylpyrrolidone in the solution A is 0.75 mmol / L; the molar concentration of the thiophene monomer in the solution B is 0.25 mmol / L; and the volume ratio of the solution A to the solution B is 3.75:1.

[0011] Preferably, the molar concentration of the ammonium persulfate in the solution C is 876 mmol / L; and the volume ratio of the solution C to the solution D is 1:19.

[0012] Preferably, the mass ratio of the cellulose nanocrystal to the dry oil is 1:(8-60); the mass ratio of the dry oil to the sodium dodecyl sulfate is 60:1; and the mass concentration of the dry oil in the dry oil microcapsules is 300-450 mg / mL.

[0013] Preferably, the mass of the dry oil microcapsules accounts for 5%-35% of the mass of the double-microcapsule self-repairing aqueous polyurethane material.

[0014] Preferably, the mass of the polythiophene microcapsules accounts for 0.1%-0.5% of the mass of the double-microcapsule self-repairing aqueous polyurethane material.

[0015] Preferably, the dry oil is linseed oil, safflower seed oil, perilla seed oil or walnut oil.

[0016] Preferably, the thiophene monomer is 3,4-vinyldioxythiophene, thieno[3,4-B]-1,4-dioxin-2-methanol, 2,3-dihydrothieno[3,4-B]-1,4-dioxin-2-methane amine, 2,3-dihydrothieno[3,4-B][1,4]dioxin-2-carboxylic acid, 3,4-propylenedioxythiophene or 3,4-(2,2-dimethylpropylenedioxy)thiophene.

[0017] Preferably, the non-polar solvent is acetonitrile, tetrahydrofuran, N,N-dimethylformamide or dimethyl sulfoxide.

[0018] In a second aspect, the present application provides a double microcapsule self-repairing waterborne polyurethane material.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] By using the Pickering emulsion template stabilized by cellulose nanocrystals to successfully encapsulate the drying oil, the high efficient coating and storage stability of the repairing agent are ensured; meanwhile, the polythiophene microcapsules prepared by the interfacial polymerization method not only act as mechanical reinforcing fillers, but also synergistically act with the drying oil microcapsules during crack propagation, and significantly accelerate the oxidation crosslinking solidification process of the drying oil through the free radicals generated by photocatalysis. The double microcapsule self-repairing system provided by the present application not only realizes the rapid self-repairing under room temperature and natural light conditions, but also enhances the mechanical properties of the double microcapsule self-repairing waterborne polyurethane material. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0022] Figure 1 The electron scanning electron microscope image of the double microcapsule self-repairing material after damage of the present application;

[0023] Figure 2 The electron scanning electron microscope image of the double microcapsule self-repairing material after damage of the present application, repaired for 5 minutes under natural light and room temperature;

[0024] Figure 3 The electron scanning electron microscope image of the double microcapsule self-repairing material after damage of the present application, repaired for 10 minutes under natural light and room temperature;

[0025] Figure 4 The electron scanning electron microscope image of the double microcapsule self-repairing material after damage of the present application, repaired for 45 minutes under natural light and room temperature;

[0026] Figure 5 Laser confocal three-dimensional image of the double microcapsule self-repairing material after damage of the present application;

[0027] Figure 6 In-situ laser confocal three-dimensional image of the double microcapsule self-repairing material after damage of the present application under natural light and at room temperature after 45 min of repair;

[0028] Figure 7 Stress-strain mechanical property test diagram of the double microcapsule self-repairing material of the present application. DETAILED DESCRIPTION

[0029] To enable persons skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the specification shall prevail.

[0030] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting on the scope of the present application, i.e., the present application can be practiced without regard to any particular theory or mechanism.

[0031] Herein, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0032] Herein, unless otherwise specified, "comprise", "include", "contain", "have" or similar words encompass the meaning of "consist of" and "consist essentially of", for example, "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".

[0033] Herein, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of the technical features, each technical feature in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope disclosed in the specification.

[0034] The present application will be further described in detail below with reference to the accompanying drawings:

[0035] The first object of the present application is to provide a preparation method of a double microcapsule self-repairing waterborne polyurethane material, comprising the following steps:

[0036] Polyvinylpyrrolidone (preferred molecular weight) M w Solution A was obtained by dissolving thiophene monomers in deionized water (40000); solution B was obtained by dissolving thiophene monomers in a nonpolar solvent; solution C was obtained by dissolving ammonium persulfate in deionized water; solution D was obtained by mixing solutions A and B and ultrasonically dispersing the mixture; solution D was obtained by mixing solutions C and D and stirring to carry out a polymerization reaction; after the polymerization reaction was completed, a polythiophene microcapsule suspension was obtained; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, the precipitated solid was washed and vacuum dried at 60-80 °C for 16-24 h to obtain polythiophene microcapsules;

[0037] Cellulose nanocrystals were ultrasonically dispersed in deionized water to form an aqueous phase; drying oil and sodium dodecyl sulfate were added to the aqueous phase, and after stirring, drying oil microcapsules with Pickering emulsion as a template were obtained.

[0038] Drying oil microcapsules and polythiophene microcapsules are added to waterborne polyurethane, mixed evenly, coated onto a substrate, and dried at room temperature to form a double-microcapsule self-healing waterborne polyurethane material.

[0039] Polythiophene microcapsules contain a large number of π-electron conjugated systems, where π electrons are easily delocalized and enhanced into free states. Under natural light irradiation, polythiophene microcapsules can excite a large number of photoelectrons to jump to the conduction band, thereby reducing oxygen in the air to superoxide radicals. In a relatively humid environment, hydrogen ions in water molecules can convert superoxide radicals into hydroxyl radicals. Simultaneously, drying oil microcapsules, as a natural reactive oxygen species scavenger, can effectively absorb these superoxide and hydroxyl radicals, thus significantly accelerating their own oxidative polymerization reaction. This invention mixes these two types of microcapsules and incorporates them into waterborne polyurethane to form a dual-capsule self-healing material with highly efficient self-healing properties. It can repair damaged areas of waterborne polyurethane materials without heating, under room temperature and natural light conditions.

[0040] Furthermore, the use of Pickering emulsion templates ensures the stability of the drying oil emulsion, effectively preventing emulsion melting and ensuring the storage and release performance of the repair material. Meanwhile, polythiophene microcapsules, in addition to their catalytic function, also act as reinforcing fillers to improve the material's mechanical properties. When microcracks appear in the material, the drying oil microcapsules rupture and release at the damage site, allowing the liquid drying oil to flow and penetrate into the crack. Simultaneously, the polythiophene microcapsules not only enhance the material's mechanical strength but also significantly improve the curing efficiency of the drying oil through photocatalysis. The two types of microcapsules work synergistically and complement each other during the repair process, thereby significantly improving the material's self-healing efficiency and mechanical properties, enabling it to maintain excellent performance stability even under various harsh environments.

[0041] The molar concentration of polyvinylpyrrolidone in solution A is 0.75 mmol / L; the molar concentration of the thiophene monomer in solution B is 0.25 mmol / L; and the volume ratio of solution A to solution B is 3.75:1. The polyvinylpyrrolidone, as a high-efficiency emulsifier and stabilizer, has a concentration sufficient to fully coat the oil droplets of the thiophene monomer and prevent polymerization thereof, thereby providing an ideal reaction interface for subsequent interfacial polymerization; and the concentration of the thiophene monomer ensures that there is sufficient raw material for polymerization at the oil-water interface, thereby successfully preparing polythiophene microcapsules with uniform capsule walls and good monodispersity.

[0042] The molar concentration of ammonium persulfate in solution C is 876 mmol / L; and the volume ratio of solution C to solution D is 1:19. The ammonium persulfate at this concentration ensures that it can still provide a sufficient amount of initiator after dilution, effectively driving the oxidative polymerization of the thiophene monomer at the oil-water interface to form an intact microcapsule wall. At the same time, the lower concentration of ammonium persulfate avoids problems such as excessively violent reaction, local overheating, or agglomeration due to an instantaneous excess of initiator, thereby ensuring a smooth and controllable polymerization process.

[0043] The mass ratio of cellulose nanocrystals to drying oil is 1:(8-60), which ensures that the cellulose nanocrystals can fully cover the surface of the drying oil droplets, forming a dense and stable Pickering emulsion interface film that effectively prevents the coalescence of oil droplets and lays a foundation for the preparation of microcapsules with good monodispersity. The mass ratio of drying oil to sodium dodecyl sulfate is 60:1, and sodium dodecyl sulfate, as an auxiliary emulsifier, can further reduce the interfacial tension and produce a synergistic stabilizing effect with cellulose nanocrystals, significantly improving the kinetic stability of the emulsion.

[0044] In addition, the mass concentration of drying oil in the drying oil microcapsules is 300-450 mg / mL, which significantly increases the loading capacity of the repair agent and ensures the repair efficiency. On the other hand, it keeps the emulsion with suitable rheological properties, ensuring good compatibility and dispersion stability when it is subsequently compounded with a waterborne polyurethane matrix, thereby successfully preparing drying oil microcapsules with high encapsulation efficiency, high stability, and large repair capacity.

[0045] The mass of the drying oil microcapsules accounts for 5%-35% of the mass of the double-microcapsule self-repairing waterborne polyurethane material, ensuring that the material can release a sufficient amount of repair agent when damaged to effectively fill cracks. The mass of the polythiophene microcapsules accounts for 0.1%-0.5% of the mass of the double-microcapsule self-repairing waterborne polyurethane material, and a small amount of polythiophene microcapsules fully plays its role in photocatalysis to produce active free radicals under natural light, significantly accelerating the curing and crosslinking process of the repair agent.

[0046] The two kinds of microcapsules are compounded in the waterborne polyurethane material as functional fillers. The dry oil microcapsule realizes good interface combination with the matrix by virtue of the hydrogen bond formed between the hydroxyl on the surface of the shell layer cellulose nanocrystal and the hydroxyl and amino in the molecular chain of the waterborne polyurethane; when the material bears tensile load, the liquid dry oil in the microcapsule can slowly seep out through the shell layer micropore, form a “lubricating-plasticizing” effect in the molecular chain of the waterborne polyurethane, reduce the internal friction resistance between the molecular chains, and at the same time, the spherical structure can induce the dispersion of the tensile stress to the surrounding matrix, reducing the local stress concentration; the polythiophene microcapsule forms a continuous “rigid support network” inside the waterborne polyurethane matrix; during the stretching process, the polythiophene microcapsule acts as a “stress bearing unit” and efficiently transfers the external load to the molecular chain of the waterborne polyurethane through the interface hydrogen bond and van der Waals force, inhibiting the excessive slip of the molecular chain, and at the same time, the rigid characteristics endowed by the conjugated structure can enhance the tensile deformation resistance of the material.

[0047] The two kinds of microcapsules form a “flexible plasticizing-rigid supporting” synergistic effect: the dry oil microcapsule improves the tensile plasticity of the material, the polythiophene microcapsule guarantees the tensile strength, and the two synergistically regulate the movement ability and stress transfer efficiency of the molecular chain of the waterborne polyurethane material, realizing the synchronous optimization of the tensile strength and plasticity.

[0048] Among them, the dry oil is linseed oil (LO), safflower seed oil, perilla seed oil or walnut oil, etc. These natural oils contain a high proportion of unsaturated fatty acids in their molecular structure, and the carbon-carbon double bond has excellent oxidation activity. When the material is damaged and the microcapsule is broken, these oils can rapidly undergo oxidation crosslinking reaction under the action of free radicals generated by the photocatalysis of polythiophene microcapsules, forming a dense network of solid film, effectively filling and sealing the cracks.

[0049] The thiophene monomers are 3,4-ethylenedioxythiophene, thieno[3,4-B]-1,4-dioxin-2-methanol, 2,3-dihydrothiophene[3,4-B]-1,4-dioxin-2-methane amine, 2,3-dihydrothieno[3,4-B][1,4]dioxin-2-carboxylic acid, 3,4-propylenedioxythiophene or 3,4-(2,2-dimethylpropylenedioxy)thiophene, etc. These monomers all contain an electron-rich conjugated system and a modifiable functional group in their molecular structure. Such monomers can form highly regular polythiophene molecular chains during interface polymerization, constructing a microcapsule shell with excellent photocatalytic activity and electrical conductivity. The special conjugated structure ensures that the microcapsule can efficiently generate free radicals under natural light, significantly accelerating the oxidation crosslinking solidification rate of the dry oil.

[0050] Nonpolar solvents such as acetonitrile, tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide exhibit excellent solubility for thiophene monomers, forming a homogeneous and stable oil-phase solution that provides an ideal reaction environment for interfacial polymerization. Simultaneously, these solvents possess appropriate immiscibility with the aqueous phase, effectively maintaining the stability of the oil-water interface and ensuring the orderly conduct of the polymerization reaction at the interface, thereby forming densely packed, regularly shaped polythiophene microcapsules.

[0051] The second objective of this invention is to provide a dual-microcapsule self-healing waterborne polyurethane material. This material uses waterborne polyurethane as a matrix, in which a specific ratio of drying oil repair microcapsules and polythiophene catalytic-reinforcing microcapsules are uniformly dispersed. When microcracks develop in this material due to external force, the stress at the crack tip causes both types of microcapsules to rupture simultaneously. The liquid repair agent (drying oil) released from the drying oil microcapsules rapidly penetrates and fills the crack voids through capillary action. Simultaneously, the polythiophene microcapsules not only act as reinforcing fillers to improve the mechanical strength of the cracked area, but the thiophene monomers exposed after rupture immediately generate a catalytic effect under natural light irradiation, significantly accelerating the oxidative cross-linking and curing process of the drying oil through photogenerated free radicals, thereby achieving rapid self-repair of the cracks. Meanwhile, compared with pure waterborne polyurethane materials, the tensile strength and elongation at break of the dual-microcapsule self-healing waterborne polyurethane material of this invention are simultaneously optimized. The tensile strength is increased from 5.7 MPa to a maximum of 8.69 MPa, and the elongation at break is increased from 800% to a maximum of 1873%, achieving simultaneous optimization of high strength and high toughness.

[0052] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0053] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0054] Example 1

[0055] Add polyvinylpyrrolidone (molecular weight) to the reagent bottle M wA solution was prepared by adding polyvinylpyrrolidone and deionized water into a reagent bottle and stirring until the polyvinylpyrrolidone was dissolved, to obtain solution A, the molar concentration of polyvinylpyrrolidone in solution A was 0.75 mmol / L; a solution B was prepared by adding 3,4-ethylenedioxythiophene and acetonitrile into a reagent bottle and stirring until the 3,4-ethylenedioxythiophene was dissolved, the molar concentration of 3,4-ethylenedioxythiophene in solution B was 0.25 mmol / L; a solution C was prepared by adding ammonium persulfate and deionized water into a reagent bottle and stirring until the ammonium persulfate was dissolved, the molar concentration of ammonium persulfate in solution C was 876 mmol / L; a solution E was prepared by mixing ethanol and water in a volume ratio of 1:1;

[0056] Solution A and solution B were mixed in a volume ratio of 3.75:1 and ultrasonic dispersion was performed to obtain solution D; solution C and solution D were mixed in a volume ratio of 1:19, stirring was performed to carry out the polymerization reaction, and after the polymerization reaction was completed, a polythiophene microcapsule suspension was obtained; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, the precipitated solid was washed three times with solution E, and after vacuum drying at 60 °C for 24 h, the polythiophene microcapsule was obtained.

[0057] A solution E was prepared by mixing ethanol and water in a volume ratio of 1:1; a solution F was prepared by adding cellulose nanocrystals and deionized water into a reagent bottle and ultrasonic dispersion was performed, then flaxseed oil and sodium dodecyl sulfate were added, and magnetic stirring was performed for 24 h to obtain flaxseed oil microcapsules with Pickering emulsion as a template; the mass concentration of flaxseed oil in the flaxseed oil microcapsules was 300 mg / mL, and the mass ratio of cellulose nanocrystals, flaxseed oil and sodium dodecyl sulfate was 7.5:60:1.

[0058] An aqueous polyurethane was used as a base material, flaxseed oil microcapsules and polythiophene microcapsules were added thereto, and after stirring and mixing uniformly, drying was performed at room temperature for 12 h to form a double-microcapsule self-repairing aqueous polyurethane material. The mass of the flaxseed oil microcapsules accounted for 5% of the mass of the double-microcapsule self-repairing aqueous polyurethane material; the mass of the polythiophene microcapsules accounted for 0.1% of the mass of the double-microcapsule self-repairing aqueous polyurethane material.

[0059] Performance test:

[0060] The samples of the double-microcapsule self-repairing aqueous polyurethane material with scratches were repaired at room temperature for 0 min, 5 min, 10 min and 45 min, respectively, and then electron scanning electron microscopy morphology characterization was performed, as shown in FIGS. 1-4, with the increase of the repair time, the scratches were gradually repaired, at 5 min, the flaxseed oil gradually filled the scratches, at 10 min, the flaxseed oil in the scratches was gradually crosslinked and solidified, and until 45 min, the scratches were completely repaired. Figures 1-4

[0061] Figure 5 and Figure 6 ​​As shown, when the dual-microcapsule self-healing waterborne polyurethane material of this embodiment develops cracks, the linseed oil microcapsules and polythiophene microcapsules will rupture along with the cracks and release the repair agent. The polythiophene accelerates the cross-linking polymerization reaction of linseed oil, achieving self-healing of the damaged area within 45 minutes.

[0062] like Figure 7 As shown, in the tensile strength test of the dual-microcapsule self-healing waterborne polyurethane material in this embodiment, due to the addition of linseed oil microcapsules, the abundant hydroxyl groups on the surface of the cellulose nanocrystals in the capsule shell of linseed oil form hydrogen bonds with the hydroxyl and amino groups in the waterborne polyurethane molecular chains. Furthermore, the liquid oil inside the microcapsules reduces the frictional resistance between molecular chains, and its spherical structure induces the tensile stress to disperse towards the surrounding matrix, reducing local stress concentration. Therefore, compared to pure waterborne polyurethane material, its elongation at break (Strain) is increased to 1580% (pure waterborne polyurethane material is 800%), but its tensile stress (Sterst) is 6.29 MPa (pure waterborne polyurethane material is 5.7 MPa), showing a limited improvement. However, the waterborne polyurethane material with both linseed oil and polythiophene microcapsules ultimately achieves a tensile strength of 8.69 MPa and an elongation at break of 1873 MPa. The simultaneous optimization of tensile strength and plasticity is achieved by polythiophene microcapsules forming a continuous "rigid support network" inside the material. During the stretching process, the polythiophene microcapsules act as "stress-bearing units," efficiently transferring external loads to the waterborne polyurethane molecular chains through interfacial hydrogen bonds and van der Waals forces, inhibiting excessive slippage of the molecular chains, thereby enhancing the tensile strength of the material.

[0063] Example 2

[0064] Add polyvinylpyrrolidone (molecular weight) to the reagent bottle M w 40000) and deionized water were added and stirred until polyvinylpyrrolidone dissolved to obtain solution A, with a molar concentration of 0.75 mmol / L for polyvinylpyrrolidone; thieno[3,4-B]-1,4-dioxin-2-methanol and tetrahydrofuran were added to a reagent bottle and stirred until thieno[3,4-B]-1,4-dioxin-2-methanol dissolved to obtain solution B, with a molar concentration of 0.25 mmol / L for thieno[3,4-B]-1,4-dioxin-2-methanol; ammonium persulfate and deionized water were added to a reagent bottle and stirred until ammonium persulfate dissolved to obtain solution C, with a molar concentration of 876 mmol / L for ammonium persulfate; ethanol and water were mixed at a volume ratio of 1:1 to obtain solution E;

[0065] Mix solution A and solution B at a volume ratio of 3.75:1 and perform ultrasonic dispersion to obtain solution D; mix solution C and solution D at a volume ratio of 1:19, stir to perform polymerization, and obtain polythiophene microcapsule suspension after the polymerization is completed; centrifuge the polythiophene microcapsule suspension until the supernatant is colorless, wash the precipitated solid with solution E three times, and obtain polythiophene microcapsule after drying at 60 ℃ under vacuum for 24 h;

[0066] Add cellulose nanocrystals and deionized water into a reagent bottle, perform ultrasonic dispersion, then add safflower oil and sodium dodecyl sulfate, and magnetically stir for 25 h to obtain safflower oil microcapsules with Pickering emulsion as a template; the mass concentration of safflower oil in the safflower oil microcapsules is 350 mg / mL, and the mass ratio of cellulose nanocrystals, safflower oil and sodium dodecyl sulfate is 1:15:0.25;

[0067] Add safflower oil microcapsules and polythiophene microcapsules to water-based polyurethane as a base material, stir and mix uniformly, then dry at room temperature for 14 h to form a double-microcapsule self-repairing water-based polyurethane material. The mass of safflower oil microcapsules accounts for 10% of the mass of the double-microcapsule self-repairing water-based polyurethane material; the mass of polythiophene microcapsules accounts for 0.1% of the mass of the double-microcapsule self-repairing water-based polyurethane material.

[0068] When the double-microcapsule self-repairing water-based polyurethane material in this embodiment generates a crack, the safflower oil microcapsules and the polythiophene microcapsules will rupture along with the generation of the crack and release repair agents, and through the acceleration of polythiophene and the cross-linking polymerization reaction of safflower oil, the self-healing of the damaged part is realized in 45 min. The tensile strength of the double-microcapsule self-repairing water-based polyurethane material in this embodiment is improved to 8.43 MPa, and the elongation at break is improved to 1833%, realizing the synchronous optimization of tensile strength and plasticity.

[0069] Example 3

[0070] Add polyvinylpyrrolidone (molecular weight M wA solution was prepared by adding polyvinylpyrrolidone and deionized water into a reagent bottle and stirring until the polyvinylpyrrolidone was dissolved, to obtain solution A, the molar concentration of polyvinylpyrrolidone in solution A was 0.75 mmol / L; a solution B was prepared by adding 2,3-dihydrothiophene [3,4-B]-1,4-dioxane-2-methane amine and N,N-dimethylformamide into a reagent bottle and stirring until the 2,3-dihydrothiophene [3,4-B]-1,4-dioxane-2-methane amine was dissolved, the molar concentration of 2,3-dihydrothiophene [3,4-B]-1,4-dioxane-2-methane amine in solution B was 0.25 mmol / L; a solution C was prepared by adding ammonium persulfate and deionized water into a reagent bottle and stirring until the ammonium persulfate was dissolved, the molar concentration of ammonium persulfate in solution C was 876 mmol / L; a solution E was prepared by mixing ethanol and water in a volume ratio of 1:1;

[0071] A solution D was prepared by mixing solution A and solution B in a volume ratio of 3.75:1 and ultrasonic dispersion; a polythiophene microcapsule suspension was obtained by mixing solution C and solution D in a volume ratio of 1:19 and stirring for polymerization reaction; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, the precipitated solid was washed twice with solution E, and the polythiophene microcapsule was obtained after vacuum drying at 65 ℃ for 22 h;

[0072] A perkin emulsion template perilla seed oil microcapsule was prepared by adding cellulose nanocrystal and deionized water into a reagent bottle and ultrasonic dispersion, then adding perilla seed oil and sodium dodecyl sulfate and stirring magnetically for 26 h; the mass concentration of perilla seed oil in the perilla seed oil microcapsule was 400 mg / mL, and the mass ratio of cellulose nanocrystal, perilla seed oil and sodium dodecyl sulfate was 1:18:0.3;

[0073] A double microcapsule self-repairing waterborne polyurethane material was formed by adding perilla seed oil microcapsules and polythiophene microcapsules into waterborne polyurethane as a base material, stirring and mixing uniformly, and drying at room temperature for 12 h; the mass of perilla seed oil microcapsules accounted for 15% of the mass of the double microcapsule self-repairing waterborne polyurethane material; the mass of polythiophene microcapsules accounted for 0.2% of the mass of the double microcapsule self-repairing waterborne polyurethane material.

[0074] When the double microcapsule self-repairing waterborne polyurethane material in this embodiment cracked, the perilla seed oil microcapsules and the polythiophene microcapsules would break and release repair agents along with the generation of cracks, and the crosslinking polymerization of perilla seed oil was accelerated by polythiophene, achieving self-healing of the damaged part in 50 min. The tensile strength of the double microcapsule self-repairing waterborne polyurethane material in this embodiment was improved to 7.56 MPa, and the elongation at break was improved to 1728%, achieving simultaneous optimization of tensile strength and plasticity.

[0075] Example 4

[0076] Add polyvinylpyrrolidone (molecular weight) to the reagent bottle M w 40000) and deionized water were added and stirred until polyvinylpyrrolidone dissolved to obtain solution A, with a molar concentration of 0.75 mmol / L for polyvinylpyrrolidone; 2,3-dihydrothieno[3,4-B][1,4]dioxin-2-carboxylic acid and dimethyl sulfoxide were added to a reagent bottle and stirred until 2,3-dihydrothieno[3,4-B][1,4]dioxin-2-carboxylic acid dissolved to obtain solution B, with a molar concentration of 0.25 mmol / L for 2,3-dihydrothieno[3,4-B][1,4]dioxin-2-carboxylic acid; ammonium persulfate and deionized water were added to a reagent bottle and stirred until ammonium persulfate dissolved to obtain solution C, with a molar concentration of 876 mmol / L for ammonium persulfate; ethanol and water were mixed at a volume ratio of 1:1 to obtain solution E;

[0077] Solution A and solution B were mixed at a volume ratio of 3.75:1 and ultrasonically dispersed to obtain solution D; solution C and solution D were mixed at a volume ratio of 1:19 and stirred to carry out a polymerization reaction. After the polymerization reaction was completed, a polythiophene microcapsule suspension was obtained; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, the precipitated solid was washed four times with solution E, and then vacuum dried at 70 °C for 20 h to obtain polythiophene microcapsules;

[0078] Cellulose nanocrystals and deionized water were added to a reagent bottle, and after ultrasonic dispersion, walnut oil and sodium lauryl sulfate were added. The mixture was magnetically stirred for 24 h to obtain walnut oil microcapsules with Pickering emulsion as a template. The mass concentration of walnut oil in the walnut oil microcapsules was 450 mg / mL, and the mass ratio of cellulose nanocrystals, walnut oil and sodium lauryl sulfate was 1:42:0.7.

[0079] Using waterborne polyurethane as the matrix material, walnut oil microcapsules and polythiophene microcapsules were added, and after stirring and mixing evenly, the mixture was dried at room temperature for 16 hours to form a dual-microcapsule self-healing waterborne polyurethane material. The walnut oil microcapsules accounted for 25% of the mass of the dual-microcapsule self-healing waterborne polyurethane material, and the polythiophene microcapsules accounted for 0.3% of the mass.

[0080] In this embodiment, when cracks appear in the dual-microcapsule self-healing waterborne polyurethane material, the walnut oil microcapsules and polythiophene microcapsules rupture along with the cracks, releasing a repair agent. The polythiophene accelerates the cross-linking polymerization reaction of the walnut oil, achieving self-healing of the damaged area within 55 minutes. In this embodiment, the tensile strength of the dual-microcapsule self-healing waterborne polyurethane material is increased to 7.12 MPa, and the elongation at break is increased to 1698%, achieving simultaneous optimization of tensile strength and plasticity.

[0081] Example 5

[0082] Add polyvinylpyrrolidone (molecular weight) to the reagent bottle M w 40000) and deionized water were added to a reagent bottle and stirred until polyvinylpyrrolidone dissolved to obtain solution A, with a molar concentration of 0.75 mmol / L for polyvinylpyrrolidone; 3,4-propylidene dioxothiophene and acetonitrile were added to a reagent bottle and stirred until 3,4-propylidene dioxothiophene dissolved to obtain solution B, with a molar concentration of 0.25 mmol / L for 3,4-propylidene dioxothiophene; ammonium persulfate and deionized water were added to a reagent bottle and stirred until ammonium persulfate dissolved to obtain solution C, with a molar concentration of 876 mmol / L for ammonium persulfate; ethanol and water were mixed at a volume ratio of 1:1 to obtain solution E;

[0083] Solution A and solution B were mixed at a volume ratio of 3.75:1 and ultrasonically dispersed to obtain solution D; solution C and solution D were mixed at a volume ratio of 1:19 and stirred to carry out a polymerization reaction. After the polymerization reaction was completed, a polythiophene microcapsule suspension was obtained; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, the precipitated solid was washed three times with solution E, and then vacuum dried at 75 °C for 18 h to obtain polythiophene microcapsules;

[0084] Cellulose nanocrystals and deionized water were added to a reagent bottle, and after ultrasonic dispersion, walnut oil and sodium dodecyl sulfate were added. The mixture was magnetically stirred for 24 h to obtain walnut oil microcapsules with Pickering emulsion as a template. The mass concentration of walnut oil in the walnut oil microcapsules was 300 mg / mL, and the mass ratio of cellulose nanocrystals, walnut oil and sodium dodecyl sulfate was 1:54:0.9.

[0085] Using waterborne polyurethane as the matrix material, walnut oil microcapsules and polythiophene microcapsules were added, and after stirring and mixing evenly, the mixture was dried at room temperature for 12 hours to form a dual-microcapsule self-healing waterborne polyurethane material. The walnut oil microcapsules accounted for 30% of the mass of the dual-microcapsule self-healing waterborne polyurethane material, and the polythiophene microcapsules accounted for 0.4% of the mass.

[0086] In this embodiment, when cracks appear in the dual-microcapsule self-healing waterborne polyurethane material, the walnut oil microcapsules and polythiophene microcapsules rupture along with the cracks, releasing a repair agent. The polythiophene accelerates the cross-linking polymerization reaction of the walnut oil, achieving self-healing of the damaged area within 45 minutes. In this embodiment, the tensile strength of the dual-microcapsule self-healing waterborne polyurethane material is increased to 8.11 MPa, and the elongation at break is increased to 1814%, achieving simultaneous optimization of tensile strength and plasticity.

[0087] Example 6

[0088] Add polyvinylpyrrolidone (molecular weight) to the reagent bottle M w The following steps were performed: 1. Add 40000 ml of ethanol and deionized water, stirring until polyvinylpyrrolidone (PVP) dissolved to obtain solution A, with a PPVP molar concentration of 0.75 mmol / L. 2. Add 3,4-(2,2-dimethylpropenyldioxy)thiophene and acetonitrile to a reagent bottle, stirring until 3,4-(2,2-dimethylpropenyldioxy)thiophene dissolved to obtain solution B, with a 3,4-(2,2-dimethylpropenyldioxy)thiophene molar concentration of 0.25 mmol / L. 3. Add ammonium persulfate and deionized water to a reagent bottle, stirring until ammonium persulfate dissolved to obtain solution C, with an ammonium persulfate molar concentration of 876 mmol / L. 4. Mix ethanol and water at a volume ratio of 1:1 to obtain solution E.

[0089] Solution A and solution B were mixed at a volume ratio of 3.75:1 and ultrasonically dispersed to obtain solution D; solution C and solution D were mixed at a volume ratio of 1:19 and stirred to carry out a polymerization reaction. After the polymerization reaction was completed, a polythiophene microcapsule suspension was obtained; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, the precipitated solid was washed three times with solution E, and then vacuum dried at 80 °C for 16 h to obtain polythiophene microcapsules;

[0090] Cellulose nanocrystals and deionized water were added to a reagent bottle, and after ultrasonic dispersion, walnut oil and sodium lauryl sulfate were added. The mixture was magnetically stirred for 24 h to obtain walnut oil microcapsules with Pickering emulsion as a template. The mass concentration of walnut oil in the walnut oil microcapsules was 450 mg / mL, and the mass ratio of cellulose nanocrystals, walnut oil and sodium lauryl sulfate was 1:60:1.

[0091] Using waterborne polyurethane as the matrix material, walnut oil microcapsules and polythiophene microcapsules were added, and after stirring and mixing evenly, the mixture was dried at room temperature for 12 hours to form a dual-microcapsule self-healing waterborne polyurethane material. The walnut oil microcapsules accounted for 35% of the mass of the dual-microcapsule self-healing waterborne polyurethane material, and the polythiophene microcapsules accounted for 0.5% of the mass.

[0092] In this embodiment, when cracks appear in the dual-microcapsule self-healing waterborne polyurethane material, the walnut oil microcapsules and polythiophene microcapsules rupture along with the cracks, releasing a repair agent. The polythiophene accelerates the cross-linking polymerization reaction of the walnut oil, achieving self-healing of the damaged area within 45 minutes. In this embodiment, the tensile strength of the dual-microcapsule self-healing waterborne polyurethane material is increased to 8.09 MPa, and the elongation at break is increased to 1789%, achieving simultaneous optimization of tensile strength and plasticity.

[0093] The above only is the preferred embodiment of the present application, and is not used to limit the present application, for those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a dual-microcapsule self-healing waterborne polyurethane material, characterized in that, Includes the following steps: Cellulose nanocrystals were ultrasonically dispersed in deionized water to form an aqueous phase; drying oil and sodium dodecyl sulfate were added to the aqueous phase, and drying oil microcapsules were obtained after stirring. Polyvinylpyrrolidone was dissolved in deionized water to obtain solution A; thiophene monomers were dissolved in a nonpolar solvent to obtain solution B; ammonium persulfate was dissolved in deionized water to obtain solution C; solutions A and B were mixed and ultrasonically dispersed to obtain solution D; solutions C and D were mixed and stirred to carry out a polymerization reaction, and after the polymerization reaction was completed, a polythiophene microcapsule suspension was obtained; the polythiophene microcapsule suspension was centrifuged until the supernatant was colorless, and the precipitated solid was washed and vacuum dried to obtain polythiophene microcapsules; The drying oil microcapsules and the polythiophene microcapsules are added to waterborne polyurethane, mixed evenly, and dried at room temperature to form the dual-microcapsule self-healing waterborne polyurethane material.

2. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The molar concentration of polyvinylpyrrolidone in solution A is 0.75 mmol / L; the molar concentration of thiophene monomer in solution B is 0.25 mmol / L; and the volume ratio of solution A to solution B is 3.75:

1.

3. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The molar concentration of ammonium persulfate in solution C is 876 mmol / L; the volume ratio of solution C to solution D is 1:

19.

4. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The mass ratio of the cellulose nanocrystals to the drying oil is 1:(8~60); the mass ratio of the drying oil to the sodium dodecyl sulfate is 60:1, and the mass concentration of the drying oil in the drying oil microcapsules is 300~450 mg / mL.

5. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The mass of the dry oil microcapsules accounts for 5% to 35% of the mass of the dual-microcapsule self-healing waterborne polyurethane material.

6. The method for preparing a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The mass of the polythiophene microcapsules accounts for 0.1% to 0.5% of the mass of the dual-microcapsule self-healing waterborne polyurethane material.

7. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The drying oil is flaxseed oil, safflower seed oil, perilla seed oil, or walnut oil.

8. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The thiophene monomers are 3,4-ethylenedioxythiophene, thieno[3,4-B]-1,4-dioxin-2-methanol, 2,3-dihydrothiophene[3,4-B]-1,4-dioxin-2-methaneamine, 2,3-dihydrothieno[3,4-B][1,4]dioxin-2-carboxylic acid, 3,4-propylenedioxythiophene, or 3,4-(2,2-dimethylpropenedioxy)thiophene.

9. The preparation method of a dual-microcapsule self-healing waterborne polyurethane material according to claim 1, characterized in that, The nonpolar solvent is acetonitrile, tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide.

10. A dual-microcapsule self-healing waterborne polyurethane material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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