Halloysite modified polyurethane with dynamic bond crosslinking function as well as preparation method and application of halloysite modified polyurethane

Abstract

The invention provides halloysite modified polyurethane with dynamic bond crosslinking as well as a preparation method and application of halloysite modified polyurethane, and belongs to the technical field of polymer composite materials. According to the method, guanidyl modified halloysite and polyurethane with dynamic disulfide bonds are firstly prepared, a'modified halloysite-dynamic disulfide bond-polyurethane network 'ternary synergistic enhancement system is constructed, and through multi-scale interface design and a dynamic bonding strategy, synergistic improvement of the mechanical property and the self-repairing property of the material is achieved. Specifically, through the synergistic effect of the nano reinforced phase and the dynamic cross-linked network, the material has ultrahigh strength and excellent toughness at the same time. Through a double reversible exchange mechanism of dynamic disulfide bonds and hydrogen bonds, efficient self-repairing of the material is achieved, and the technical problem that a high-strength material is poor in fatigue resistance is solved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to an halloysite-modified polyurethane with dynamic bond crosslinking, its preparation method, and its application. Background Technology

[0002] With the rapid development of modern industrial technology, the demand for high-performance polymer materials in key fields such as aerospace, intelligent manufacturing, and engineering machinery is becoming increasingly urgent. Among them, polyurethane materials, with their excellent mechanical properties, good wear resistance, and environmental adaptability, have become indispensable functional materials in high-end equipment manufacturing. However, research has found that traditional polyurethane materials, under long-term dynamic loads, suffer from performance degradation due to the initiation and propagation of microcracks. This not only leads to sudden failure accidents but also significantly reduces the service life of critical components, posing a serious threat to the reliable operation of equipment systems. Developing novel polyurethane composite materials with high strength, high toughness, excellent fatigue resistance, and self-healing properties provides a research approach to solving these problems. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide an halloysite-modified polyurethane with dynamic bond crosslinking, its preparation method, and its application. The halloysite-modified polyurethane prepared by this invention exhibits high strength, high toughness, excellent fatigue resistance, and self-healing properties.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing halloysite-modified polyurethane with dynamic bond crosslinking, comprising the following steps: A carbodiimide reagent, a silane coupling agent, and a weakly polar organic solvent are mixed and subjected to an addition reaction to obtain a silane modifier containing a guanidine group. Halloysite, the guanidine-containing silane modifier, and a polar organic solvent were mixed and grafted to obtain guanidine-modified halloysite. A solution of isocyanate-terminated polyurethane prepolymer was mixed with a carboxyl-containing polyol chain extender to carry out a chain extension reaction, thereby obtaining a carboxyl-containing chain-extended product. The carboxyl-containing chain extension product is mixed with a diamine chain extender containing a disulfide bond to carry out an amino chain extension reaction, thereby obtaining an amino chain extension product. The amino chain extender is mixed with a multifunctional crosslinking agent and a crosslinking reaction is carried out to obtain a polyurethane solution with dynamic bond crosslinking. The polyurethane solution with dynamic bond crosslinking was mixed with guanidine-modified halloysite to carry out a hydrogen bonding reaction, and the organic solvent was removed to obtain halloysite-modified polyurethane with dynamic bond crosslinking.

[0005] Preferably, the carbodiimide reagent includes N,N'-diisopropylcarbodiimide and / or dicyclohexylcarbodiimide; The silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane; The addition reaction is carried out at a temperature of 80~120℃ for 12~24h.

[0006] Preferably, the grafting reaction is carried out at a temperature of 60-100°C for 6-10 hours.

[0007] Preferably, the method for preparing the isocyanate-terminated polyurethane prepolymer solution includes the following steps: Diol, organic solvent, diisocyanate, and catalyst are mixed and subjected to a prepolymerization reaction to obtain a polyurethane prepolymer solution with terminal isocyanate groups. The molar ratio of the diol to the diisocyanate is 1:1 to 4.

[0008] Preferably, the carboxyl-containing polyol chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, and bis(2-hydroxyethyl)propionic acid; The molar ratio of the carboxyl-containing polyol chain extender to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is 1:3~10. The chain extension reaction is carried out at a temperature of 40-80℃ for 2-5 hours.

[0009] Preferably, the diamine chain extender containing disulfide bonds includes one or more of 4,4'-diaminodiphenyl disulfide, 2,2'-diaminodiphenyl disulfide, and bis(2-aminoethyl) disulfide; The molar ratio of the diamine chain extender containing disulfide bonds to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is 1:3~5. The amino chain extension reaction is carried out at a temperature of 40~80℃ for a time of 0.5~3h.

[0010] Preferably, the multifunctional crosslinking agent includes one or more of trimethylolpropane, triethanolamine, and diethanolamine; The molar ratio of the multifunctional crosslinking agent to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is 1:5~10. The cross-linking reaction is carried out at a temperature of 30~60℃ for a time of 0.5~2h.

[0011] Preferably, the mass of the guanidine-modified halloysite is 0.25-3% of the mass of the polyurethane with dynamic bond crosslinking; The hydrogen bonding reaction is carried out at a temperature of 40-80℃ for 1-3 hours.

[0012] This invention provides halloysite-modified polyurethane with dynamic bond crosslinking prepared by the above preparation method.

[0013] This invention provides the application of the above-mentioned halloysite-modified polyurethane with dynamic bond crosslinking in aerospace materials, intelligent vehicle structural components, or soft robot drive systems.

[0014] This invention provides a method for preparing halloysite-modified polyurethane with dynamic bond crosslinking. The method involves first preparing guanidine-modified halloysite and polyurethane with dynamic disulfide bonds, and then constructing a ternary synergistic reinforcement system of "modified halloysite-dynamic disulfide bond-polyurethane network". This invention achieves a synergistic improvement in the material's mechanical properties and self-healing properties through multi-scale interface design and a dynamic bonding strategy. Specifically, this synergistic effect is manifested at the molecular structure level: the guanidine groups on the modified halloysite surface form numerous reversible hydrogen bonds with the polyurethane chains, significantly enhancing interfacial interactions and effectively transferring and dispersing stress; simultaneously, the dynamic disulfide bonds can undergo reversible breakage and recombination under stress, dissipating energy and preventing microcrack propagation; the synergistic effect of these two elements constructs a continuous and reversible physical crosslinking network at the nanoscale, which not only significantly improves the material's strength and toughness but also endows it with highly efficient self-healing capabilities.

[0015] Specifically, this invention utilizes the synergistic effect of modified halloysite nano-reinforcing phase and dynamic cross-linking network to enable materials to simultaneously possess ultra-high strength and excellent toughness. Example results show that adding only trace amounts of modified halloysite can increase the tensile strength of polyurethane to 46.6 MPa and the toughness to a high level of 150.6 MJ / m. 3This invention represents a significant improvement over traditional polyurethane materials. Through a dual reversible exchange mechanism of dynamic disulfide bonds and hydrogen bonds, the invention achieves highly efficient self-healing of the material. Even after repair, the tensile strength remains above 40 MPa, with a self-healing efficiency exceeding 90%, greatly extending the material's service life. Furthermore, this invention creatively solves the technical challenge of poor fatigue resistance in high-strength materials. The principle behind its excellent fatigue resistance lies in the fact that under cyclic loading, the dynamic disulfide and hydrogen bond network within the material can continuously dissipate energy through reversible fracture and recombination, effectively inhibiting the accumulation of micro-damage and preventing crack initiation and propagation caused by stress concentration. Simultaneously, halloysite nanotubes, as a rigid reinforcing phase, effectively share and transfer local stress, maintaining the integrity of the network structure. After 100 cycles of tensile testing at 150% strain, the polyurethane material still maintains stable mechanical recovery properties, exhibiting excellent fatigue resistance. This invention provides a new approach for developing high-performance structural-functional integrated polyurethane materials. Its superior comprehensive performance makes it valuable for applications in key aerospace components, protective materials for defense equipment, intelligent automotive structural components, and soft robot drive systems.

[0016] Furthermore, the preparation method provided by this invention is simple to operate, low in cost, and easy to achieve industrial-scale mass production. Attached Figure Description

[0017] Figure 1 Synthetic steps for halloysite-modified polyurethane with dynamic bond crosslinking; Figure 2 Infrared spectra of APTMS, DIC, and m-APTMS; Figure 3 Infrared spectra of m-APTMS, HNTs, and M-HNTs; Figure 4 Infrared spectra of Comparative Example 1 and Examples 1-3; Figure 5 This is a schematic diagram of the stress-strain curves for the first 100 cycles of Example 2; Figure 6 This is a schematic diagram of the stress-strain curves for the second 100 cycles of Example 2; Figure 7 The stress values ​​corresponding to 150% strain in the 1st, 20th, 40th, 60th, 80th, and 100th cycles of the first 100 cycles and the second 100 cycles of Example 2, respectively; Figure 8 The stress-strain curves are shown for the initial and repaired states in Example 2. Detailed Implementation

[0018] This invention provides a method for preparing halloysite-modified polyurethane with dynamic bond crosslinking, comprising the following steps: A carbodiimide reagent, a silane coupling agent, and a weakly polar organic solvent are mixed and subjected to an addition reaction to obtain a silane modifier containing a guanidine group. Halloysite, the guanidine-containing silane modifier, and a polar organic solvent were mixed and grafted to obtain guanidine-modified halloysite. A solution of isocyanate-terminated polyurethane prepolymer was mixed with a carboxyl-containing polyol chain extender to carry out a chain extension reaction, thereby obtaining a carboxyl-containing chain-extended product. The carboxyl-containing chain extension product is mixed with a diamine chain extender containing a disulfide bond to carry out an amino chain extension reaction, thereby obtaining an amino chain extension product. The amino chain extender is mixed with a multifunctional crosslinking agent and a crosslinking reaction is carried out to obtain a polyurethane solution with dynamic bond crosslinking. The polyurethane solution with dynamic bond crosslinking was mixed with guanidine-modified halloysite to carry out a hydrogen bonding reaction, and the organic solvent was removed to obtain halloysite-modified polyurethane with dynamic bond crosslinking.

[0019] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0020] This invention involves mixing a carbodiimide reagent, a silane coupling agent, and a weakly polar organic solvent to perform an addition reaction, thereby obtaining a silane modifier containing a guanidine group. In this invention, the carbodiimide reagent includes N,N'-diisopropylcarbodiimide (DIC) and / or dicyclohexylcarbodiimide (DCC); the silane coupling agent preferably includes one or more of γ-aminopropyltrimethoxysilane (APTMS), γ-aminopropyltriethoxysilane (APTES), and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (GPTMS). In this invention, the molar ratio of the carbodiimide reagent to the silane coupling agent is preferably 1 to 3:1, specifically 1:1, 2:1, or 3:1.

[0021] In this invention, the weakly polar organic solvent preferably includes one or more of anhydrous toluene, xylene, and dichloromethane. In this invention, the addition reaction is preferably carried out in an oil bath, with stirring and under nitrogen protection. The temperature of the addition reaction is preferably 80-120°C, more preferably 90-100°C, and the time is preferably 12-24 hours, more preferably 16-20 hours. After the addition reaction, the organic solvent is preferably removed by vacuum distillation to obtain an amber-colored guanidine-containing silane modifier, denoted as m-Silane.

[0022] After obtaining the guanidine-containing silane modifier, the present invention mixes halloysite, the guanidine-containing silane modifier, and a polar organic solvent to perform a grafting reaction to obtain guanidine-modified halloysite. In the present invention, the mass ratio of halloysite to the guanidine-containing silane coupling agent is preferably 1:1 to 3, specifically 1:1, 1:2, or 1:3. In the present invention, the polar organic solvent preferably includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP). In the present invention, the mixing method is preferably as follows: first, halloysite and the polar organic solvent are ultrasonically mixed, and then the guanidine-containing silane modifier is added. In the present invention, the ultrasonic mixing power is preferably 200 to 500 W, more preferably 300 to 400 W, and the time is preferably 0.5 to 2 h, more preferably 1 to 1.5 h.

[0023] In this invention, the grafting reaction is preferably carried out under oil bath and stirring conditions. The temperature of the grafting reaction is preferably 60-100℃, more preferably 70-80℃, and the time is preferably 6-10h, more preferably 7-8h. During the grafting reaction, the alkoxysilane of m-Silane hydrolyzes and condenses with the hydroxyl groups on the surface of HNTs to form a covalent graft, yielding guanidinyl-modified halloysite, denoted as M-HNTs. After the grafting reaction, the obtained grafting reaction solution is preferably centrifuged, washed, and dried.

[0024] This invention involves mixing an isocyanate-terminated polyurethane prepolymer solution with a carboxyl-containing polyol chain extender to perform a chain extension reaction, thereby obtaining a carboxyl-containing chain-extended product. In this invention, the preparation method of the isocyanate-terminated polyurethane prepolymer solution preferably includes the following steps: Diol, organic solvent, diisocyanate, and catalyst are mixed and subjected to a prepolymerization reaction to obtain a polyurethane prepolymer solution with terminal isocyanate groups.

[0025] In this invention, the diol preferably includes one or more of polycaprolactone diol (PCL), polytetrahydrofuran ether diol (PTMG), and polycarbonate diol (PCDL), and the molecular weight of the diol is preferably 1000-2000, more preferably 1500-2000; the diisocyanate preferably includes one or more of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and diphenylmethane diisocyanate (MDI). In this invention, the molar ratio of the diol to the diisocyanate is preferably 1:1-4, more preferably 1:2-3.

[0026] In this invention, the catalyst is preferably one or more of dibutyltin dilaurate, stannous isooctanoate, and zinc isooctanoate; the mass ratio of the catalyst to the diisocyanate is preferably 1:100~300, more preferably 1:150~200.

[0027] In this invention, the organic solvent preferably includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP). In this invention, the mixing method is preferably as follows: first, the diol is mixed with the organic solvent, then dehydrated, and then the diisocyanate and catalyst are added. In this invention, the dehydration is preferably carried out under oil bath and stirring conditions, the dehydration temperature is preferably 120°C, and the dehydration time is preferably 120 min.

[0028] In this invention, the prepolymerization reaction is preferably carried out in a nitrogen atmosphere, the temperature of the prepolymerization reaction is preferably 70~100℃, more preferably 80~90℃, and the time is preferably 2~5h, more preferably 3~4h. After the prepolymerization reaction, this invention preferably does not perform any post-processing and directly uses it for the next reaction.

[0029] In this invention, the carboxyl-containing polyol chain extender preferably includes one or more of dimethylolpropionic acid (DMPA), dimethylolbutyric acid (DMBA), and bis(2-hydroxyethyl)propionic acid; the molar ratio of the carboxyl-containing polyol chain extender to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is preferably 1:3~10, more preferably 1:4~8. In this invention, the chain extension reaction is preferably carried out in a nitrogen atmosphere, the temperature of the chain extension reaction is preferably 40~80℃, more preferably 50~60℃, and the time is preferably 2~5h, more preferably 3~4h. The main function of this chain extension step is to introduce side carboxyl groups into the polyurethane molecular chain using the carboxyl-containing polyol chain extender, providing sites for subsequent hydrogen bond formation, and simultaneously initially extending the molecular chain length and adjusting the molecular weight of the prepolymer. After the chain extension reaction, this invention preferably does not perform post-processing and directly uses it for the next reaction.

[0030] After obtaining the carboxyl-containing chain-extended product, the present invention mixes the carboxyl-containing chain-extended reaction product with a diamine chain extender containing disulfide bonds to carry out an amino chain-extending reaction, thereby obtaining an amino chain-extended product. In the present invention, the diamine chain extender containing disulfide bonds preferably includes one or more of 4,4'-diaminodiphenyl disulfide, 2,2'-diaminodiphenyl disulfide, and bis(2-aminoethyl) disulfide. The molar ratio of the diamine chain extender containing disulfide bonds to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is preferably 1:3~5, more preferably 1:4. This amino chain extension step is a key step, and its core function is to utilize the high reactivity of amino groups and isocyanates to precisely introduce disulfide-bonded segments into the polyurethane backbone, constructing a reversible dynamic covalent cross-linked network, and endowing the material with highly efficient self-healing properties. In this invention, the preferred temperature for the amino chain extension reaction is 40-80°C, more preferably 50-60°C, and the preferred time is 0.5-3 hours, more preferably 1-2 hours. After the amino chain extension reaction, this invention preferably does not perform any post-treatment and directly uses the product for the next reaction.

[0031] After obtaining the amino chain-extended product, the present invention mixes the amino chain-extended product with a multifunctional crosslinking agent to carry out a crosslinking reaction, thereby obtaining a polyurethane solution with dynamic bond crosslinking. In the present invention, the multifunctional crosslinking agent preferably includes one or more of trimethylolpropane (TMP), triethanolamine (TEA), and diethanolamine (DEA), and the molar ratio of the multifunctional crosslinking agent to the diisocyanate used to prepare the isocyanate-terminated polyurethane prepolymer solution is preferably 1:5~10, more preferably 1:6~8. The role of this crosslinking reaction is to utilize the multifunctional crosslinking agent to establish a three-dimensional network structure between multiple molecular chains, significantly improving the mechanical strength and stability of the material; at the same time, in synergy with the dynamic disulfide bonds and carboxyl sites introduced in the previous steps, a multi-network structure of "rigid crosslinked network - dynamic covalent bond - reversible physical interaction" is finally formed, thereby achieving a synergistic improvement in mechanical properties and self-healing efficiency. In this invention, the temperature of the crosslinking reaction is preferably 30~60℃, more preferably 40~50℃, and the time is preferably 0.5~2h, more preferably 1~1.5h. After the crosslinking reaction, this invention preferably does not perform any post-processing and directly uses the material for the next reaction.

[0032] After obtaining the dynamically cross-linked polyurethane solution, the present invention mixes the dynamically cross-linked polyurethane solution with guanidine-modified halloysite and performs a hydrogen bonding reaction to remove the organic solvent, thereby obtaining a dynamically cross-linked halloysite-modified polyurethane. In the present invention, the mass of the guanidine-modified halloysite is preferably 0.25-3% of the mass of the dynamically cross-linked polyurethane, more preferably 0.5-2.5%, and even more preferably 1-2%. In the present invention, the temperature of the hydrogen bonding reaction is preferably 40-80℃, more preferably 50-60℃, and the time is preferably 1-3 hours, more preferably 2 hours. In the present invention, during the hydrogen bonding process, the guanidine groups in the guanidine-modified halloysite undergo hydrogen bonding with the carboxyl groups in the polyurethane structure.

[0033] In this invention, the method for removing the organic solvent is preferably drying, more preferably vacuum drying. In this invention, the drying temperature is preferably 40-80°C, more preferably 50-60°C, and the drying time is preferably 24-48 hours, more preferably 30-40 hours. In this invention, before drying, the obtained hydrogen-bonded reaction solution is preferably cast, and after drying, an halloysite-modified polyurethane film with dynamic bond crosslinking is obtained. In this invention, the thickness of the film is preferably 0.3-0.7 mm.

[0034] This invention provides halloysite-modified polyurethane with dynamic bond crosslinking prepared by the above preparation method.

[0035] This invention provides the application of the above-mentioned halloysite-modified polyurethane with dynamic bond crosslinking in aerospace materials, intelligent vehicle structural components, or soft robot drive systems.

[0036] The following detailed description, in conjunction with embodiments, illustrates the halloysite-modified polyurethane with dynamic bond crosslinking provided by the present invention, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 (1) N,N'-diisopropylcarbodiimide (DIC) (6.44 g, 50 mmol) and γ-aminopropyltriethoxysilane (APTMS) (11.29 g, 50 mmol) were dissolved in 50 mL of anhydrous toluene and reacted in an oil bath at 100 °C for 24 h under nitrogen protection. After the reaction was completed, toluene was removed by vacuum distillation to obtain the modified silane coupling agent (m-APTMS), and the reaction formula is shown in formula a: Formula a.

[0038] (2) Halloysite (HNTs) (1.49 g, 5 mmol) and M-APTMS (1.53 g, 5 mmol) were mixed and added to 50 mL of organic solvent DMF. The mixture was stirred in an oil bath at 80 °C for 8 h. After the reaction was completed, the modified halloysite (M-HNTs) was obtained by centrifugation, washing and drying. The reaction formula is shown in formula b: Formula b.

[0039] (3) Weigh 3 mmol, 6.0 g of polycarbonate diol (PCDL-2000) with a molecular weight of 2000 g / mol and 10 mL of DMF and mix them in a three-necked flask. Stir for 2 h in an oil bath at 120 °C and under N2 atmosphere. After the system cools down to 80 °C, add 10 mL of DMF solution of isophorone diisocyanate (IPDI) (1.83 g, 8.25 mmol) dropwise to the reaction flask and add the catalyst dibutyltin dilaurate (DBTDL) (0.01 g). Stir the reaction at 80 °C for 3 h to obtain isocyanate-terminated polyurethane prepolymer. (4) Dissolve 0.13 g, 1 mmol of dimethylolpropionic acid (DMPA) in 5 mL of DMF and slowly add it dropwise to the reaction system. Stir the reaction at 60 °C for 3 h to achieve chain extension. (5) Dissolve 4,4'-diaminodiphenyl disulfide (DTDA) (0.50 g, 2 mmol) in 7 mL DMF, add it dropwise to the reaction system, and stir at 60 °C for 1 h to complete the amino chain extension; (6) Dissolve trimethylolpropane (TMP) (0.20 g, 1.5 mmol) in 5 mL of DMF, add it dropwise to the reaction system, and stir at 40 °C for 1 h to complete the crosslinking; (7) Disperse 0.25 wt.% of M-HNTs (0.0332 g) in 5 mL of DMF, add to the reaction system, stir at 60 °C for 2 h to make M-HNTs uniformly dispersed in the polyurethane matrix. After the reaction is completed, 8.69 g of polyurethane is obtained. The reaction solution is poured into a polytetrafluoroethylene mold and vacuum dried at 80 °C for 24 h to remove residual solvent, thus obtaining halloysite-modified polyurethane with dynamic bond crosslinking.

[0040] The preparation flow chart of halloysite-modified polyurethane with dynamic bond crosslinking is as follows: Figure 1 As shown.

[0041] Example 2 The difference from Example 1 is that the amount of M-HNTs added is 0.5 wt.% of M-HNTs (0.0663 g).

[0042] Example 3 The difference from Example 1 is that the amount of M-HNTs added is 1.0 wt.% of M-HNTs (0.1326 g).

[0043] Example 4 The difference from Example 1 is that in step (3), polytetrahydrofuran ether diol (PTMG) with a molecular weight of 2000 g / mol is used instead of polycarbonate diol (PCDL), while the amount remains the same.

[0044] Example 5 The difference from Example 1 is that in step (5), an equimolar amount of bis(2-aminoethyl) disulfide (0.37 g, 2 mmol) is used instead of 4,4'-diaminodiphenyl disulfide (DTDA).

[0045] Comparative Example 1 The difference from Example 1 is that the preparation of M-HNTs in steps (1) and (2) and the addition of M-HNTs in step (7) are omitted, resulting in a polyurethane with dynamic bond crosslinking.

[0046] Comparative Example 2 The difference from Example 1 is that in step (5), an equimolar amount of the common chain extender 1,4-butanediol (BDO) (0.18 g, 2 mmol) is used instead of 4,4'-diaminodiphenyl disulfide (DTDA), and the introduction of dynamic disulfide bonds is omitted.

[0047] Comparative Example 3 The difference from Example 1 is that the chain extension process in step (4) is omitted (DMPA is not added), and the chain extension order is adjusted: after obtaining the prepolymer in step (3), 4,4'-diaminodiphenyl disulfide (DTDA) is added first for amino chain extension, then TMP is added for crosslinking, and finally M-HNTs are added.

[0048] Structural characterization (1) Figure 2 The images show the infrared spectra of APTMS, DIC, and m-APTMS. The results indicate that the peak intensity at 3440 cm⁻¹ is [missing information]. -1 The vibration at 1100 cm⁻¹ belongs to the stretching vibration of the NH bond in DIC; -1 The location is the stretching vibration of the Si-OC bond in APTMS; 1460 cm⁻¹ -1 The vibration is a symmetrical stretching vibration with -N=C=N- at 2150cm. -1 The asymmetric stretching vibration at position -N=C=N- in DIC indicates that m-APTMS was successfully prepared.

[0049] (2) Figure 3The infrared spectra of m-APTMS, HNTs, and M-HNTs are shown. The results indicate that at 1460 cm⁻¹... -1 The vibration is a symmetrical stretching vibration of -N=C=N- in m-APTMS, located at 3620 cm. -1 and 3698 cm -1 The adsorption peak at the point is attributed to the stretching vibration of Al-OH and the stretching vibration of its internal OH, indicating that halloysite modification was successful.

[0050] (3) Figure 4 The images show the infrared spectra of Comparative Example 1 and Examples 1-3. The results show that at 1250 cm⁻¹... -1 The stretching vibrations at 2260-2280 cm⁻¹ are attributed to the CO bonds in the carbamate; -1 The absence of the -NCO peak indicates that IPDI has reacted completely, and the peaks are located at 3620 and 3698 cm⁻¹. -1 The adsorption peak at the point is attributed to the stretching vibration of Al-OH and the stretching vibration of its internal OH, indicating the successful preparation of polyurethane material.

[0051] Performance testing (1) Mechanical property analysis To effectively evaluate the mechanical properties of the prepared polyurethane materials, stress-strain curve tests were performed on all samples from Comparative Example 1 and Examples 1-3. The results are summarized in Table 1. The test standard was GB / T 1040-2006, the test speed was 50 mm / min, and the test environment was 25℃.

[0052] Table 1. Elongation at break, ultimate tensile strength, and toughness of Comparative Examples 1-3 and Examples 1-5

[0053] As shown in Table 1, all examples exhibit superior overall mechanical properties compared to the comparative examples. In particular, Example 2, with only 0.5 wt.% guanidine-modified halloysite (M-HNTs) added, achieved a tensile strength of 46.64 MPa, an elongation at break of 940.63%, and a toughness as high as 150.60 MJ / m. 3 The results show that the material's strength, ductility, and toughness are significantly better than those of unmodified or partially modified comparative samples. This result fully demonstrates that the three-dimensional network structure synergistically constructed by introducing functionalized halloysite and dynamic disulfide bonds effectively enhances the material's strength, ductility, and toughness, achieving a synergistic improvement in mechanical properties.

[0054] Furthermore, Examples 4 and 5, by changing the type of polyol and the disulfide bond extender, respectively, further verified the universality and controllability of the preparation method, indicating that the material system has good structural design flexibility and performance optimization space.

[0055] (2) Fatigue resistance analysis To systematically evaluate the fatigue resistance and shape recovery characteristics of the material, the sample of Example 2 was subjected to 200 consecutive cyclic tensile tests at a tensile rate of 50 mm / min and a constant strain of 150%, including the initial 100 cycles and the subsequent 100 cycles after heat treatment at 80°C for recovery.

[0056] Figure 5 The stress-strain curves for the first 100 cycles in Example 2 are shown. The first cycle exhibits a significant hysteresis loop phenomenon, attributed to energy dissipation caused by the breaking and rearrangement of sacrificial bonds (such as supramolecular interactions like hydrogen bonds) within the material. As the number of cycles increases, the hysteresis loop area gradually decreases and stabilizes after 70 cycles, indicating that the dynamic bond network within the material reaches equilibrium, demonstrating excellent fatigue resistance.

[0057] After 100 cycles, the sample completely recovered its initial state after heat treatment at 80℃ for 5 minutes, confirming that the material exhibits a significant thermally induced shape memory effect. The results of the subsequent second 100-cycle test are as follows... Figure 6 As shown in the figure, the results indicate that the recovered sample still maintains a mechanical response behavior similar to that of the initial test.

[0058] Figure 7 The stress values ​​corresponding to 150% strain in the first 100 cycles and the second 100 cycles of Example 2 are shown. Comparative analysis of the stress values ​​in the two test cycles at the characteristic cycle numbers (1, 20, 40, 60, 80, and 100) revealed that the difference in stress response between the two tests was less than 5%, fully demonstrating that the polyurethane material not only possesses excellent initial mechanical properties but also exhibits outstanding elastic recovery and long-term fatigue resistance. Even after 200 cycles of tensile testing, the material maintains stable mechanical properties.

[0059] (3) Self-healing performance analysis To systematically evaluate the self-healing performance of the material, a standard fracture-repair test was performed on the sample from Example 2: after cutting the sample with a knife, it was placed in an oven at 80℃ for 8 hours for heat treatment. According to GB / T 1040-2006 standard, the mechanical properties before and after repair were tested at 25℃ and a tensile rate of 50 mm / min.

[0060] Figure 8The stress-strain curves for Example 2, both initially and after repair, show that the repaired material retains over 85% of its original strength. This excellent repair efficiency stems from the synergistic effect of dynamic covalent bonds (disulfide bonds) and non-covalent bonds (hydrogen bonds) introduced into the material's molecular design: during heat treatment, the reversible breakage / reorganization of dynamic bonds promotes the re-entanglement of molecular chains at the fracture interface. Extending the heat treatment time significantly improves the exchange efficiency of dynamic bonds at the fracture interface. When the temperature rises to 80°C, the rapid dynamic exchange of disulfide bonds and the reconstruction of the hydrogen bond network form a synergistic repair mechanism, enabling the material to achieve effective self-repair within 8 hours. This provides a new approach for developing long-lasting and stable self-healing materials.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing halloysite-modified polyurethane with dynamic bond crosslinking, characterized in that, Includes the following steps: A carbodiimide reagent, a silane coupling agent, and a weakly polar organic solvent are mixed and subjected to an addition reaction to obtain a silane modifier containing a guanidine group. Halloysite, the guanidine-containing silane modifier, and a polar organic solvent were mixed and grafted to obtain guanidine-modified halloysite. A solution of isocyanate-terminated polyurethane prepolymer was mixed with a carboxyl-containing polyol chain extender to carry out a chain extension reaction, thereby obtaining a carboxyl-containing chain-extended product. The carboxyl-containing chain extension product is mixed with a diamine chain extender containing a disulfide bond to carry out an amino chain extension reaction, thereby obtaining an amino chain extension product. The amino chain extender is mixed with a multifunctional crosslinking agent and a crosslinking reaction is carried out to obtain a polyurethane solution with dynamic bond crosslinking. The polyurethane solution with dynamic bond crosslinking was mixed with guanidine-modified halloysite to carry out a hydrogen bonding reaction, and the organic solvent was removed to obtain halloysite-modified polyurethane with dynamic bond crosslinking.

2. The preparation method according to claim 1, characterized in that, The carbodiimide reagents include N,N'-diisopropylcarbodiimide and / or dicyclohexylcarbodiimide; The silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane; The addition reaction is carried out at a temperature of 80~120℃ for 12~24h.

3. The preparation method according to claim 1 or 2, characterized in that, The grafting reaction is carried out at a temperature of 60~100℃ for 6~10h.

4. The preparation method according to claim 1, characterized in that, The method for preparing the isocyanate-terminated polyurethane prepolymer solution includes the following steps: Diol, organic solvent, diisocyanate, and catalyst are mixed and subjected to a prepolymerization reaction to obtain a polyurethane prepolymer solution with terminal isocyanate groups. The molar ratio of the diol to the diisocyanate is 1:1 to 4.

5. The preparation method according to claim 1 or 4, characterized in that, The carboxyl-containing polyol chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, and bis(2-hydroxyethyl)propionic acid; The molar ratio of the carboxyl-containing polyol chain extender to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is 1:3~10. The chain extension reaction is carried out at a temperature of 40-80℃ for 2-5 hours.

6. The preparation method according to claim 1 or 4, characterized in that, The diamine chain extender containing disulfide bonds includes one or more of 4,4'-diaminodiphenyl disulfide, 2,2'-diaminodiphenyl disulfide, and bis(2-aminoethyl) disulfide; The molar ratio of the diamine chain extender containing disulfide bonds to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is 1:3~5. The amino chain extension reaction is carried out at a temperature of 40~80℃ for a time of 0.5~3h.

7. The preparation method according to claim 1 or 4, characterized in that, The multifunctional crosslinking agent includes one or more of trimethylolpropane, triethanolamine, and diethanolamine; The molar ratio of the multifunctional crosslinking agent to the diisocyanate used in preparing the isocyanate-terminated polyurethane prepolymer solution is 1:5~10. The cross-linking reaction is carried out at a temperature of 30~60℃ for a time of 0.5~2h.

8. The preparation method according to claim 1 or 4, characterized in that, The mass of the guanidine-modified halloysite is 0.25-3% of the mass of the polyurethane with dynamic bond crosslinking; The hydrogen bonding reaction is carried out at a temperature of 40-80℃ for 1-3 hours.

9. Halloysite-modified polyurethane with dynamic bond crosslinking prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the halloysite-modified polyurethane with dynamic bond crosslinking as described in claim 9 in aerospace materials, intelligent automotive structural components, or soft robot drive systems.

Images