阅读说明：本技术 一种高强度自修复水性聚氨酯复合材料及其制备方法 (High-strength self-repairing waterborne polyurethane composite material and preparation method thereof ) 是由 孔米秋 徐文卿 吕亚栋 黄亚江 李光宪 于 2021-02-04 设计创作，主要内容包括：本发明涉及一种基于金属有机配位键实现高强度和自修复性能的绿色环保水性聚氨酯材料及其制备方法,属于高分子合成和智能高分子材料领域。本发明提供一种高强度自修复水性聚氨酯复合材料,所述复合材料由邻苯二酚封端的水性聚氨酯与金属氧化物通过配位反应制得。本发明选择以四氧化三铁纳米粒子等金属氧化物为增强填料,利用金属-有机配体配位键优异自修复和刺激响应的特性,得到高强度快速自修复的水性聚氨酯复合材料。(The invention relates to a green environment-friendly waterborne polyurethane material capable of realizing high strength and self-repairing performance based on metal organic coordination bonds and a preparation method thereof, belonging to the field of polymer synthesis and intelligent polymer materials. The invention provides a high-strength self-repairing waterborne polyurethane composite material which is prepared by performing coordination reaction on catechol-terminated waterborne polyurethane and metal oxide. According to the invention, metal oxides such as ferroferric oxide nanoparticles are selected as reinforcing fillers, and the characteristics of excellent self-repairing and stimulus response of metal-organic ligand coordination bonds are utilized to obtain the high-strength rapid self-repairing waterborne polyurethane composite material.)

1. The high-strength self-repairing waterborne polyurethane composite material is characterized in that the composite material is prepared by carrying out coordination reaction on catechol-terminated waterborne polyurethane and metal oxide.

2. The high strength self-healing aqueous polyurethane composite of claim 1, wherein the molar ratio of catechol terminated aqueous polyurethane to metal oxide is: 1-3: 1.

3. the high-strength self-repairing aqueous polyurethane composite material according to claim 1 or 2, wherein the catechol-terminated aqueous polyurethane is prepared by the following method: adding polymer diol, an anionic hydrophilic chain extender, diisocyanate and a catalyst into a reaction device provided with a condensation reflux device and a mechanical stirring device, and reacting at 70-90 ℃ for 2-5 h to obtain an isocyanate-terminated waterborne polyurethane prepolymer; then adding an anionic salt forming agent, adding water under mechanical stirring for full emulsification, then adding a catechol compound, and reacting for 1-2 h to obtain a catechol-terminated aqueous polyurethane emulsion;

further, the catechol compound is selected from the group consisting of: dopamine, nitrocatechol, chlorocatechol, or 3-hydroxy-4-pyridone.

4. The high-strength self-repairing waterborne polyurethane composite material according to any one of claims 1 to 3, wherein the metal oxide is one of ferroferric oxide, vanadium trioxide, aluminum oxide, calcium oxide or magnesium oxide.

5. The high-strength self-repairing aqueous polyurethane composite material according to any one of claims 1 to 4, wherein the molar ratio of the polymer diol to the anionic hydrophilic chain extender to the diisocyanate is: 0.5-1.0: 0.5-1.0: 1.5 to 4;

further, the mass of the catalyst is 0.3-0.5% of that of the polymer diol;

further, the molar ratio of the anionic salt forming agent to the anionic hydrophilic chain extender is 9-10: 10;

further, the molar ratio of the catechol compound to the diisocyanate is 33-100: 100.

6. the high-strength self-repairing aqueous polyurethane composite material according to any one of claims 1 to 5, wherein the polymer diol is one of polyether diol, polyester diol or polycarbonate diol;

further, the polyether diol is at least one of polypropylene oxide diol, polytetrahydrofuran ether diol, polyethylene glycol or polytetramethylene ether glycol; the polyester diol is at least one of polyethylene glycol adipate diol, polyethylene glycol phthalate diol or polycaprolactone diol;

preferably, the polymer diol is polyether diol, more preferably at least one of polyethylene glycol, polytetrahydrofuran ether glycol or polytetramethylene ether glycol;

further, the anionic hydrophilic chain extender is one of a chain extender containing carboxyl or a sulfonate chain extender;

further, the chain extender containing carboxyl is dimethylolpropionic acid, dimethylolbutyric acid, tartaric acid or half-ester diol; the sulfonate chain extender is diaminoalkane sulfonate, 2-sodium sulfonate-1, 4-butanediol or 2, 4-diaminobenzene sulfonic acid;

further, the diisocyanate is one of aliphatic diisocyanate, alicyclic diisocyanate or aromatic diisocyanate;

still further, the aliphatic diisocyanate is 1, 6-hexamethylene diisocyanate or trimethyl-1, 6-hexamethylene diisocyanate; the alicyclic diisocyanate is isophorone diisocyanate, 1, 4-cyclohexane diisocyanate, dicyclohexylmethane diisocyanate or methylcyclohexyl diisocyanate; the aromatic diisocyanate is toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate or dimethyl biphenyl diisocyanate;

preferably, the diisocyanate is alicyclic diisocyanate, more preferably one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1, 4-cyclohexane diisocyanate or cyclohexanedimethylene diisocyanate;

further, the catalyst is diethylene diamine, bis [2- (N, N-dimethylaminoethyl) ], trimethylhydroxyethylpropylene diamine, dibutyltin dilaurate or stannous octoate; preferably one of dibutyltin dilaurate or stannous octoate;

further, the anionic salt forming agent is one of sodium hydroxide, ammonia water or triethylamine.

7. The preparation method of the high-strength self-repairing waterborne polyurethane composite material as claimed in any one of claims 1 to 6, wherein the preparation method comprises the following steps: adding metal oxide into catechol terminated aqueous polyurethane emulsion, uniformly dispersing the metal oxide, and then performing ligand exchange reaction at 0-40 ℃ to obtain the high-strength self-repairing aqueous polyurethane composite material.

8. The preparation method of the high-strength self-repairing aqueous polyurethane composite material as claimed in claim 7, wherein the method for adding the metal oxide into the catechol-terminated aqueous polyurethane emulsion and uniformly dispersing the metal oxide comprises the following steps: firstly, modifying metal oxide with oleic acid or tannic acid, then ultrasonically dispersing the metal oxide in deionized water uniformly, and then dropwise adding the metal oxide into catechol-terminated waterborne polyurethane emulsion;

further, in the preparation method of the high-strength self-repairing waterborne polyurethane composite material, the pH value of a reaction system is 7-12.

9. The preparation method of the high-strength self-repairing aqueous polyurethane composite material according to claim 7 or 8, wherein when the metal oxide is ferroferric oxide, the preparation method of the high-strength self-repairing aqueous polyurethane composite material comprises the following steps: firstly, modifying ferroferric oxide by adopting oleic acid or tannic acid; then dropwise adding ferroferric oxide modified by oleic acid or tannic acid into catechol-terminated aqueous polyurethane emulsion; finally, ligand exchange reaction is carried out at 0-40 ℃ to obtain the high-strength self-repairing waterborne polyurethane composite material.

10. The preparation method of the high-strength self-repairing waterborne polyurethane composite material according to claim 9, wherein the oleic acid-modified ferroferric oxide is prepared by the following steps: putting a polar organic solvent, absolute ethyl alcohol and water into a reaction container, and continuously introducing inert gas to remove dissolved oxygen; respectively weighing FeCl₃·6H₂O、FeCl₂·4H₂O、C₁₈H₃₃O₂Sequentially adding Na and NaOH into the mixed solution, mechanically stirring the mixture in an inert gas atmosphere, and carrying out reflux reaction at the temperature of 60-80 ℃ for 4-6 h; after the reflux is finished, removing the flask from the oil bath, cooling to room temperature, precipitating the product by ethanol, performing magnetic separation, pouring out supernatant, adding a proper amount of deionized water for ultrasonic dispersion, centrifuging for at least 10min, and removing undispersed substances at the bottom; repeating the step for at least 3 times, and precipitating and magnetically separating the finally obtained upper-layer aqueous dispersion with ethanol again to obtain oleic acid-modified ferroferric oxide magnetic nanoparticles;

further, the polar organic solvent is one of toluene, cyclohexane or n-hexane.

Technical Field

The invention relates to a green environment-friendly waterborne polyurethane material capable of realizing high strength and self-repairing performance based on metal organic coordination bonds and a preparation method thereof, belonging to the field of polymer synthesis and intelligent polymer materials.

Background

The waterborne polyurethane replaces an organic solvent with water, retains the excellent characteristics of the traditional polyurethane, has the advantages of greenness, no toxicity and easy modification, is a promising multifunctional high polymer material, and is widely applied to the fields of coatings, paints, adhesives and the like. But because the glass is exposed to the environment frequently in the using process, the glass inevitably suffers collision, scratch, chemical corrosion, photo aging or combination effect of external force, so that the inner part or the outer part of the glass cracks due to microcrack, and the using efficiency of the glass is lost. Inspired by organism self-repairing damage, self-repairing materials are developed. By introducing the self-repairing performance into the waterborne polyurethane material, the damage and the crack of the material can be self-healed in time, the self-performance of the material can be better maintained, and the service life of the material can be prolonged.

Self-repairing high polymer materials are roughly divided into two types according to the repairing mechanism and the characteristics of material preparation: extrinsic self-repair and intrinsic repair. The external aid type repair is the earliest self-repairing material, including a microcapsule method, a microvascular method and the like, and a repairing agent is encapsulated in a polymer, but in such a system, the repair is difficult to be repeated due to the consumption of the encapsulating agent. Different from the external self-repairing material, the intrinsic self-repairing material has potential repairing capability, and the main intrinsic self-repairing system comprises: DA reaction-based thermal reversible crosslinking reaction, reversible acylhydrazone bonds, disulfide bonds, hydrogen bonds, ionic interactions, metal ligand complexes, and the like. Generally, the mechanical properties of the introduced reversible covalent bond are more excellent than those of the introduced non-covalent force, but the bond energy of the covalent bond is relatively high, so that the response of the reversible covalent bond requires large external stimulation, and the excellent mechanical strength and self-repairing performance are difficult to be simultaneously achieved. XU (Chemistry of Materials, 2018, 30, 6026-containing 6039) and the like use di-and tri-functional polyoxypropylene for chain extension and crosslinking through an isocyanate group and then end capping with an imidazole derivative, and induce a restoration rate of almost 100% by coordination of zinc ions with the imidazole derivative, but the tensile strength is only 2.26 MPa. Kim et al prepared a self-healing polyurethane elastomer based on aromatic disulfide bonds, which was self-healed for 25-2 h with a recovery rate of tensile strength of 88.2%, but the tensile strength of the original sample was only 6.8MPa (adv. mater.2018, 30, 1705145). Therefore, the existing self-repairing polyurethane material is difficult to simultaneously consider high strength and quick self-repairing performance.

Disclosure of Invention

Aiming at the defects, the invention provides the waterborne polyurethane composite material with excellent self-repairing performance, high strength and good comprehensive performance and the preparation method thereof. The invention selects ferroferric oxide (Fe)₃O₄) The metal oxides such as nano particles and the like are used as reinforcing fillers, and the characteristics of excellent self-repairing and stimulus response of metal-organic ligand coordination bonds are utilized to obtain the high-strength rapid self-repairing waterborne polyurethane composite material.

The technical scheme of the invention is as follows:

the invention aims to solve the first technical problem of providing a high-strength self-repairing waterborne polyurethane composite material, which is prepared by carrying out coordination reaction on catechol-terminated waterborne polyurethane and metal oxide.

Further, the molar ratio of the catechol terminated waterborne polyurethane to the metal oxide is as follows: 1-3: 1.

Further, the catechol terminated waterborne polyurethane is prepared by the following method: adding polymer diol, an anionic hydrophilic chain extender, diisocyanate and a catalyst into a reaction device provided with a condensation reflux device and a mechanical stirring device, and reacting at 70-90 ℃ for 2-5 h to obtain an isocyanate-terminated waterborne polyurethane prepolymer; and then adding an anionic salt forming agent, adding water under mechanical stirring for full emulsification, then adding a catechol compound (such as dopamine hydrochloride), and reacting for 1-2 h to obtain the catechol-terminated aqueous polyurethane emulsion.

Further, the catechol compound is selected from the group consisting of: dopamine, nitrocatechol, chlorocatechol, or 3-hydroxy-4-pyridone; the catechol compound is a catechol derivative or an analogue.

Further, the metal oxide is one of ferroferric oxide, vanadium trioxide, aluminum oxide, calcium oxide or magnesium oxide.

Further, the molar ratio of the polymer diol to the anionic hydrophilic chain extender to the diisocyanate is: 0.5-1.0: 0.5-1.0: 1.5 to 4.

Further, the mass of the catalyst is 0.3-0.5% of that of the polymer diol.

Further, the molar ratio of the anionic salt forming agent to the anionic hydrophilic chain extender is 9-10: 10.

further, the molar ratio of the catechol compound to the diisocyanate is 33-100: 100.

further, the polymer diol is one of polyether diol, polyester diol or polycarbonate diol.

Still further, the polyether glycol is at least one of polyoxypropylene glycol, polytetrahydrofuran ether glycol, polyethylene glycol or polytetramethylene ether glycol; the polyester diol is at least one of polyethylene glycol adipate diol, polyethylene glycol phthalate diol or polycaprolactone diol.

Preferably, the polymer diol is polyether diol, and more preferably at least one of polyethylene glycol, polytetrahydrofuran ether glycol or polytetramethylene ether glycol.

Further, the anionic hydrophilic chain extender is one of a chain extender containing carboxyl or a sulfonate chain extender.

Further, the chain extender containing carboxyl is dimethylolpropionic acid, dimethylolbutyric acid, tartaric acid or half-ester diol; the sulfonate chain extender is diaminoalkane sulfonate, 2-sodium sulfonate-1, 4-butanediol or 2, 4-diaminobenzene sulfonic acid.

Further, the diisocyanate is one of aliphatic diisocyanate, alicyclic diisocyanate, or aromatic diisocyanate.

Still further, the aliphatic diisocyanate is 1, 6-hexamethylene diisocyanate or trimethyl-1, 6-hexamethylene diisocyanate; the alicyclic diisocyanate is isophorone diisocyanate, 1, 4-cyclohexane diisocyanate, dicyclohexylmethane diisocyanate or methylcyclohexyl diisocyanate; the aromatic diisocyanate is toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate or dimethyl biphenyl diisocyanate.

Preferably, the diisocyanate is an alicyclic diisocyanate, and more preferably is one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1, 4-cyclohexane diisocyanate or cyclohexanedimethylene diisocyanate.

Further, the catalyst is diethylene diamine, bis [2- (N, N-dimethylaminoethyl) ], trimethylhydroxyethylpropylene diamine, dibutyltin dilaurate or stannous octoate; preferably one of dibutyltin dilaurate or stannous octoate.

Further, the anionic salt forming agent is one of sodium hydroxide, ammonia water or triethylamine.

The second technical problem to be solved by the present invention is to provide a preparation method of the high-strength self-repairing aqueous polyurethane composite material, wherein the preparation method comprises: adding metal oxide into catechol terminated aqueous polyurethane emulsion, uniformly dispersing the metal oxide, and then performing ligand exchange reaction at 0-40 ℃ to obtain the high-strength self-repairing aqueous polyurethane composite material.

Further, the method for adding the metal oxide into the catechol-terminated aqueous polyurethane emulsion and uniformly dispersing the metal oxide into the catechol-terminated aqueous polyurethane emulsion comprises the following steps: firstly, modifying metal oxide with oleic acid or tannic acid, then ultrasonically dispersing the metal oxide in deionized water uniformly (about 5 min), and then dropwise adding the metal oxide into catechol-terminated waterborne polyurethane emulsion.

Further, when the metal oxide is ferroferric oxide, the preparation method of the high-strength self-repairing aqueous polyurethane composite material comprises the following steps: firstly, modifying ferroferric oxide by oleic acid; then dropwise adding ferroferric oxide modified by oleic acid into catechol-terminated aqueous polyurethane emulsion; finally, ligand exchange reaction is carried out at 0-40 ℃ to obtain the high-strength self-repairing waterborne polyurethane composite material.

Further, the method for preparing oleic acid modified ferroferric oxide comprises the following steps: placing polar organic solvent, anhydrous ethanol and water in a reaction vessel, and continuously introducing inert gas (such as nitrogen gas for at least 30min) to remove dissolved oxygenGas; respectively weighing FeCl₃·6H₂O、FeCl₂·4H₂O、C₁₈H₃₃O₂Sequentially adding Na and NaOH into the mixed solution, mechanically stirring the mixture in an inert gas atmosphere, and carrying out reflux reaction at the temperature of 60-80 ℃ for 4-6 h; after the reflux is finished, removing the flask from the oil bath, cooling to room temperature, precipitating the product by ethanol, performing magnetic separation, pouring out supernatant, adding a proper amount of deionized water for ultrasonic dispersion, centrifuging for at least 10min, and removing undispersed substances at the bottom; repeating the steps for at least 3 times, precipitating the finally obtained upper-layer aqueous dispersion by using ethanol again, and carrying out magnetic separation to obtain the oleic acid modified ferroferric oxide magnetic nanoparticles, wherein the obtained magnetic particles have the following appearance and crystal form: uniform spherical shape, spinel-type structure with size of about 20 nm.

Further, in the preparation method of the oleic acid-modified ferroferric oxide, the polar organic solvent is one of toluene, cyclohexane or n-hexane.

Further, in the preparation method of the high-strength self-repairing waterborne polyurethane composite material, the pH value of a reaction system is 7-12. The pH value is more than 7, so that the ionization of the waterborne polyurethane prepolymer is ensured, and the waterborne polyurethane prepolymer can be emulsified in water; on the other hand, the pH increases, which increases the coordination number.

The invention has the beneficial effects that:

according to the invention, a method of adding metal oxides such as ferroferric oxide and the like into catechol-terminated waterborne polyurethane is adopted, on one hand, the tensile strength and the glass transition temperature of the waterborne polyurethane can be effectively improved due to the addition of the metal oxides; on the other hand, after metal oxide (such as oleic acid modified ferroferric oxide) is added, catechol at the molecular chain end of the waterborne polyurethane and oleic acid molecules coordinated by the ferroferric oxide perform ligand exchange reaction to form a metal-organic ligand coordination bond, and the coordination bond also has a reinforcing effect, so that the strength is greatly improved; moreover, ions and a matrix generate better coordination interaction, so that the enhancement effect is more obvious; finally, the waterborne polyurethane with excellent self-repairing performance and mechanical strength is obtained.

Drawings

FIG. 1 is a graph illustrating crack self-repair of a material obtained in example 1 of the present invention; the self-repairing test method comprises the following steps: the sample is cut into two sections, the surfaces of the two sections are placed together and are respectively placed at room temperature for one day, the two sections cut by the sample can be firmly combined together after being placed at 60 ℃ for 30min and being placed in a room temperature humid environment for 30min, obvious cracks can not be observed by naked eyes, and the crack healing condition is observed under the condition of 20 times of magnification under an optical microscope.

FIG. 2 is a stress-strain curve of the material obtained in example 1 of the present invention and a pure water polyurethane blank.

FIG. 3 shows the glass transition temperatures of the material obtained in example 1 of the present invention and a pure water-based polyurethane blank.

FIG. 4 is a graph of crack self-repair of the material obtained in example 2 of the present invention.

FIG. 5 is a stress-strain curve of the material obtained in example 2 of the present invention and a pure water polyurethane blank.

FIG. 6 shows the glass transition temperatures of the material obtained in example 2 of the present invention and a pure water-based polyurethane blank.

Detailed Description

The key point of the invention for preparing the waterborne polyurethane/metal oxide composite material is as follows: firstly, catechol is adopted to seal the waterborne polyurethane, and then metal oxide and catechol at the molecular chain end of the waterborne polyurethane are subjected to coordination reaction; the metal oxide such as ferroferric oxide is firstly modified by oleic acid, so that the metal oxide is excellent in water dispersibility, effectively inhibits agglomeration, and is easy to generate ligand exchange reaction after being doped into an aqueous polyurethane system, thereby realizing high performance and functionalization of the aqueous polyurethane.

According to the invention, the addition of metal oxides such as ferroferric oxide magnetic nanoparticles and the like can not only effectively improve the tensile strength and the glass transition temperature of the waterborne polyurethane, but also can generate a coordination bond effect with a matrix waterborne polyurethane molecular chain as a metal oxide, so that the waterborne polyurethane realizes self-healing; the formed coordination bond also has a reinforcing effect, so that the strength is greatly improved; namely, the ferroferric oxide modified waterborne polyurethane can simultaneously realize the improvement of the mechanical property and the self-repairing functionalization.

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention.

The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

A method for enhancing the mechanical property and the thermal mechanical property of self-repairing waterborne polyurethane by adopting ferroferric oxide comprises the following specific steps:

firstly, preparing oleic acid modified ferroferric oxide magnetic nanoparticles

42mL of cyclohexane, 24mL of absolute ethanol and 18mL of water were placed in a three-necked flask (volume ratio 7:4:3), and nitrogen was continuously introduced for 30min to remove dissolved oxygen. Then respectively weighing 2.16g FeCl₃·6H₂O、0.79g FeCl₂·4H₂O, 4.87g of C₁₈H₃₃O₂Na and 1.12g NaOH were sequentially added to the above mixed solution, and the mixture was mechanically stirred under a nitrogen atmosphere and reacted at 68 ℃ under reflux for 4 hours. After the reflux is finished, the flask is removed from the oil bath and cooled to room temperature, the supernatant is poured out after the product is precipitated by ethanol and is subjected to magnetic separation, deionized water is added for ultrasonic dispersion, the mixture is centrifuged for 10min, and undispersed substances at the bottom are discarded. Repeating the steps for 3 times, precipitating the upper-layer aqueous dispersion obtained finally with ethanol, and performing magnetic separation to obtain Fe modified by oleic acid₃O₄Magnetic nanoparticles.

Preparation of ferriferrous oxide and ferroferric oxide reinforced waterborne polyurethane composite material

1) In a three-necked flask equipped with a thermometer, a reflux condenser and a mechanical stirrer were placed 10g of polytetrahydrofuran ether glycol and 1.34g of DMPA (2, 2-dimethylolpropionic acid), and the mixture was mechanically stirred for 20 minutes in an oil bath at 80 ℃ to be sufficiently mixed. 6.67g (isocyanate index of 1.5 in this example) of IPDI (isophorone diisocyanate) and a suitable amount of catalyst DBTDL (dibutyltin dilaurate) were added and reacted for 3 hours. After cooling to 40 ℃, 1g of triethylamine was added to ionize the carboxylate groups in the system. Adding deionized water under high-speed strong stirring, emulsifying for 30min, adding 3.89g of dopamine hydrochloride, and reacting for 1h to obtain catechol terminated waterborne polyurethane;

2) adding 0.5g of the magnetic particles prepared in the step one into a reaction system, reacting for 30min, adding NaOH to adjust the pH value to 12, and continuing to react for 1 h;

3) and (3) removing air bubbles in vacuum for 10min, then pouring the membrane, and drying in a vacuum oven to obtain the ferroferric oxide/waterborne polyurethane composite material.

The mechanical properties of the samples were characterized using an Instron 4302 Universal tensile tester. According to the GB/T13954 test method, the prepared sample band is dumbbell-shaped, the length is 50.0 +/-1.0 mm, the gauge length is 25 +/-1.0 mm, and the width is 4.0 +/-0.2 mm. The stretching speed is 200mm/min, and the testing temperature is room temperature; the glass transition temperature (Tg) of the composite material is measured by DMA (DMTA Q800, TA of America), the measurement temperature range is-100 ℃, and the heating rate is 5 ℃/min.

The performance test results of the prepared waterborne polyurethane material are shown in the attached drawings 1-3, and it can be seen from the drawings that the tensile strength of the obtained waterborne polyurethane/ferroferric oxide composite material is 36.5MPa, which is improved by 145 percent compared with a blank sample (pure waterborne polyurethane); repairing for 2 hours at 60 ℃, wherein the self-repairing rate is 90%; the glass transition temperature is 76.3 ℃, which is increased by 49.7 ℃ compared with the blank sample.

Example 2

A method for enhancing the mechanical property and the thermal mechanical property of self-repairing waterborne polyurethane by adopting ferroferric oxide comprises the following specific steps:

firstly, preparing oleic acid modified ferroferric oxide magnetic nanoparticles

42mL of cyclohexane, 24mL of absolute ethanol and 18mL of water were placed in a three-necked flask (volume ratio 7:4:3), and nitrogen was continuously introduced for 30min to remove dissolved oxygen. Then respectively weighing 2.16g FeCl₃·6H₂O、0.79g FeCl₂·4H₂O, 4.87g of C₁₈H₃₃O₂Na and 1.12g NaOH were added to the above mixed solution in this orderThe mixture was mechanically stirred under nitrogen and reacted at 68 ℃ under reflux for 4 h. After the reflux is finished, the flask is removed from the oil bath and cooled to room temperature, the supernatant is poured out after the product is precipitated by ethanol and is subjected to magnetic separation, deionized water is added for ultrasonic dispersion, the mixture is centrifuged for 10min, and undispersed substances at the bottom are discarded. Repeating the steps for 3 times, precipitating the upper-layer aqueous dispersion obtained finally with ethanol, and performing magnetic separation to obtain Fe modified by oleic acid₃O₄Magnetic nanoparticles.

Preparation of ferriferrous oxide and ferroferric oxide reinforced waterborne polyurethane composite material

1) In a three-necked flask equipped with a thermometer, a reflux condenser and a mechanical stirrer, 10g of polytetrahydrofuran ether glycol and 1.34g of DMPA were charged, and the mixture was mechanically stirred in an oil bath at 80 ℃ for 20 minutes to be sufficiently mixed. 8.89g (isocyanate index of 2.0 in this example) of IPDI and an appropriate amount of catalyst DBTDL were added and reacted for 3 hours. After cooling to 40 ℃, 1g of triethylamine was added to ionize the carboxylate groups in the system. Adding deionized water under high-speed strong stirring, emulsifying for 30min, adding 3.89g dopamine hydrochloride, and reacting for 1 h;

2) adding 0.5g of the magnetic particles prepared in the step one into a system, reacting for 30min, adding NaOH to adjust the pH value to 12, and continuing to react for 1 h;

3) and (3) removing air bubbles in vacuum for 10min, then pouring the membrane, and drying in a vacuum oven to obtain the ferroferric oxide/waterborne polyurethane composite material.

The mechanical properties of the samples were characterized using an Instron 4302 Universal tensile tester. According to the GB/T13954 test method, the prepared sample band is dumbbell-shaped, the length is 50.0 +/-1.0 mm, the gauge length is 25 +/-1.0 mm, and the width is 4.0 +/-0.2 mm. The stretching speed is 200 mm/min; the glass transition temperature (Tg) of the composite material is measured by DMA (DMTA Q800, TA of America), the measurement temperature range is-100 ℃, and the heating rate is 5 ℃/min.

The performance test results of the prepared waterborne polyurethane material are shown in the attached drawings 1-3, and it can be seen from the drawings that the tensile strength of the obtained waterborne polyurethane/ferroferric oxide composite material is 57.7MPa, which is improved by 287% compared with a blank sample (pure waterborne polyurethane); repairing for 2 hours at 60 ℃, wherein the self-repairing rate is 73%; the glass transition temperature is 122.7 ℃, which is increased by 96.1 ℃ compared with the blank sample.