Preparation method and application of double dynamic bond self-repairing polyurethane elastomer

Abstract

The invention discloses a double dynamic bond self-repairing polyurethane elastomer as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The elastomer is prepared from the following raw materials in percentage by mass: 74 to 76 percent of polyether polyol, 15.5 to 18 percent of diisocyanate, 1.67 to 7 percent of dihydrazide compound and 2.1 to 6.7 percent of disulfide. The preparation method comprises the following steps: firstly, reacting polyether polyol with diisocyanate to obtain a prepolymer, then sequentially carrying out step-by-step chain extension reaction on the prepolymer, the bishydrazide compound and the disulfide compound, and finally, curing and forming. According to the invention, a synergistic structure of a hydrogen bond hard segment and a disulfide bond soft segment is constructed step by step, so that the material has high mechanical properties and efficient self-repairing capability. The elastomer is suitable for the fields of industrial pipeline sealing pieces, flexible packaging films, sports equipment accessories and the like, and solves the problem that the strength and repairing performance of an existing self-repairing polyurethane material are difficult to balance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a method for preparing and applying a self-healing polyurethane elastomer with dual dynamic bonds. Background Technology

[0002] Polyurethane elastomers are widely used in industrial sealing, flexible packaging, and sports equipment due to their excellent flexibility, abrasion resistance, and designability. However, traditional polyurethane materials are prone to microcracks or damage after long-term use or exposure to external forces, and lack self-healing capabilities, severely affecting their service life and reliability. To endow polyurethane materials with self-healing capabilities, dynamic covalent bonds (such as disulfide bonds) or non-covalent interactions (such as hydrogen bonds) can be introduced. If self-healing capability is provided solely by disulfide bonds, the material strength is usually low; similarly, relying on high-density hydrogen bonds to improve strength often requires stringent self-healing conditions (≥100℃ high temperature).

[0003] Existing technologies, such as CN113801288B, disclose a polyurethane damping material based on the synergistic effect of dynamic disulfide bonds and hydrogen bonds. After repairing for 24 hours at 60°C, the self-healing efficiency can reach 70% or more. However, the maximum tensile strength is only about 15 MPa, which is still difficult to adapt to structural components or load-bearing scenarios with higher mechanical performance requirements, and the application fields are greatly limited.

[0004] Therefore, given the common problem of existing polyurethane elastomers being unable to balance strength and self-healing capabilities, there is an urgent need to develop a new type of polyurethane material that can achieve efficient self-healing at medium and low temperatures and in a short time while maintaining high mechanical properties, thereby broadening its application range in harsh working conditions or long-term service environments. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying a dual dynamic bond self-healing polyurethane elastomer, solving the technical problem of "achieving efficient self-healing at medium and low temperatures and in a short time while maintaining high mechanical properties", and expanding the application scenarios of self-healing polyurethane materials.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a dual dynamic bond self-healing polyurethane elastomer, wherein the raw materials for preparing the dual dynamic bond self-healing polyurethane elastomer, by weight percentage, comprise: 74-76% polyether polyol, 15.5-18% diisocyanate, 1.67-7% dihydrazide compound, and 2.1-6.7% disulfide compound; Specifically, the polyether polyol is polytetrahydrofuran ether diol.

[0007] Specifically, the diisocyanate is isophorone diisocyanate.

[0008] Specifically, the dihydrazide compound is one or more of isophthalic acid dihydrazide and adipic acid dihydrazide.

[0009] Specifically, the disulfide compound is one or more of 4,4'-diaminodiphenyl disulfide and bis(2-hydroxyethyl) disulfide.

[0010] The reaction of the dihydrazide compound and diisocyanate of the present invention generates acylaminourea segments, which can provide multiple hydrogen bond interaction sites. These hydrogen bonds can form an ordered and regular array in the hard segments, producing a synergistic effect. When subjected to external force, they can effectively transfer and disperse stress, thereby improving the tensile strength of polyurethane. Isophorone diisocyanate has an asymmetric structure, which can inhibit the excessive crystallization of hydrogen bond hard segments and balance rigidity and toughness.

[0011] Secondly, this invention provides a method for preparing a self-healing polyurethane elastomer with dual dynamic bonds, comprising the following steps: (1) After vacuum dehydration of polyether polyol, diisocyanate, catalyst and N,N-dimethylacetamide solution are added and reacted at 60-85℃ for 2-4h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 35-45°C, add N,N-dimethylacetamide solution of dihydrazide compound, and react for 10-14 h to form hydrogen bond hard segments; at 35-45°C, add N,N-dimethylacetamide solution of disulfide compound to the hydrogen bond hard segment reaction system, and continue to react for 10-14 h to obtain the reaction solution; (3) The above-obtained reaction solution is molded and then dried and cured at 70-90°C to obtain a double dynamic bond self-healing polyurethane elastomer.

[0012] Further, in step (1), the mass of the catalyst is 0.1 to 0.15 wt% of the total mass of the polyether polyol, diisocyanate, dihydrazide compound and disulfide compound.

[0013] Furthermore, in step (1), the vacuum dehydration is carried out at 100-110°C and under a vacuum of -0.095MPa for 0.5-1h.

[0014] Furthermore, in step (2), the mass ratio of dihydrazide compound to disulfide compound is (0.25~3):1.

[0015] Thirdly, the present invention provides the application of the aforementioned dual dynamic bond self-healing polyurethane elastomer in industrial pipeline seals, flexible packaging films, and sports equipment accessories.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention first constructs dense hydrogen-bonded hard segments with isophthalic acid dihydrazide as the key component, forming a strong and ordered rigid support network that endows the material with extremely high tensile strength. Subsequently, the introduced disulfide compound forms a dynamic reversible phase in the soft segment region, which can complete efficient chain segment recombination and damage repair within 12 hours at 80°C, with a self-repair efficiency of up to 98.1%. The polyurethane elastomer has excellent mechanical properties at a repair efficiency of 81.6%, with a tensile strength of 49.2 MPa and an elongation at break of 1489%.

[0017] 2. Through the hard-segment-soft-segment structural design, this invention can achieve the transformation from ultra-high strength to ultra-high toughness without changing the basic synthesis path, simply by adjusting the ratio of hydrogen bond hard segment components to disulfide bond soft segment components. This allows it to be flexibly applied to different application scenarios, and the polyurethane elastomer still has excellent stability over a wide temperature range, meeting the usage conditions of industrial maintenance and storage environments, as well as the temperature resistance requirements of various application scenarios.

[0018] 3. The polyurethane elastomer of the present invention has good self-healing properties. The repair process mainly occurs in the dynamic soft segment region without destroying the hydrogen bond hard segment network that serves as the main strength component, thereby ensuring a high degree of recovery of the mechanical integrity of the material after repair. Attached Figure Description

[0019] Figure 1 The above are the synthesis route diagrams of polyurethane elastomers in Examples 1-7 of this invention.

[0020] Figure 2 These are the FTIR spectra of the polyurethane elastomers in Examples 1-4 of this invention.

[0021] Figure 3 These are schematic diagrams of the stress-strain curves and repair efficiency of polyurethane elastomers in Examples 1-4 of the present invention.

[0022] Figure 4 This is a schematic diagram showing the stress-strain curves and repair efficiency of the polyurethane elastomer in Embodiment 2 of the present invention at different temperatures.

[0023] Figure 5 This is a schematic diagram showing the weight changes of the polyurethane elastomers in Examples 1-4 of the present invention at different temperatures. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0025] The raw materials for preparing the self-healing polyurethane elastomer, by mass percentage, include: 74-76% polyether polyol, 15.5-18% diisocyanate, 1.67-7% diacid hydrazide compound, and 2.1-6.7% disulfide compound. In the following examples and comparative examples, unless otherwise specified, the mass of polytetrahydrofuran ether diol (Mn=2000) is 10.00g as the basis for calculating and weighing other components.

[0026] The preparation of the self-healing polyurethane elastomer includes the following steps: (1) Polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110℃ and -0.095MPa vacuum for 0.5h. Under a nitrogen atmosphere, isophorone diisocyanate, dibutyltin dilaurate and N,N-dimethylacetamide solution were added and reacted at 80℃ for 3h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen-bonded hard segments; add 4,4'-diaminodiphenyl disulfide and N,N-dimethylacetamide solution to the hydrogen-bonded hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) The above-obtained reaction solution is molded and then dried and cured at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer.

[0027] As a preferred embodiment of the present invention, the amount of the catalyst dibutyltin dilaurate is calculated as 0.13 wt% of the preset total feed mass of the polytetrahydrofuran ether diol, the isophorone diisocyanate, the isophthalic acid dihydrazide, and the 4,4'-diaminodiphenyl disulfide.

[0028] As a preferred embodiment of the present invention, the mass ratio of the isophthalic acid dihydrazide and the 4,4'-diaminodiphenyl disulfide is (0.25~3):1.

[0029] Example 1; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in industrial pipeline seals.

[0030] A schematic diagram of the synthesis process of the polyurethane elastomer is shown below. Figure 1 As shown, its preparation process includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.20 g of isophorone diisocyanate, 0.0173 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer; the NCO content was determined to be 4.7% by di-n-butylamine titration. (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.83 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.28 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) Pour the above-obtained reaction liquid into a DN200 pipe sealing gasket mold, and then dry and cure at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer; cut the double dynamic bond self-healing polyurethane elastomer into annular sealing gaskets with an inner diameter of 200 mm and a thickness of 5 mm, and test its performance.

[0031] Example 2; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in sports equipment accessories.

[0032] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.20 g of isophorone diisocyanate, 0.0173 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.67 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.45 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) Pour the above-obtained reaction liquid into the surface mold of the yoga mat, and then dry and cure it at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer; cut the double dynamic bond self-healing polyurethane elastomer into a yoga mat of 300mm×150mm×1.5mm and test its performance.

[0033] Example 3; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in flexible packaging films.

[0034] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.20 g of isophorone diisocyanate, 0.0173 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer. (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.557 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.557 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) The above-obtained reaction solution is evenly poured onto a polytetrafluoroethylene plate. The wet film thickness is controlled to be 0.15 mm using a film scraper. Then, it is placed on an 80°C heating table for 12 hours to allow it to fully cure, thus obtaining a double dynamic bond self-healing polyurethane elastomer film. The cured film is peeled off from the substrate and cut into packaging films with a size of 200 mm × 150 mm, and its performance is tested.

[0035] Example 4; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in flexible packaging films.

[0036] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.20 g of isophorone diisocyanate, 0.0173 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer. (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.223 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.89 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) The above-obtained reaction solution is evenly poured onto a polytetrafluoroethylene plate. The wet film thickness is controlled to be 0.15 mm using a film scraper. Then, it is placed on an 80°C heating table for 12 hours to allow it to fully cure, thus obtaining a double dynamic bond self-healing polyurethane elastomer film. The cured film is peeled off from the substrate and cut into packaging films with a size of 200 mm × 150 mm, and its performance is tested.

[0037] Example 5; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in sports equipment accessories.

[0038] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.4 g of isophorone diisocyanate, 0.0176 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.65 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.44 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) Pour the above-obtained reaction liquid into the surface mold of the yoga mat, and then dry and cure it at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer; cut the double dynamic bond self-healing polyurethane elastomer into a yoga mat of 300mm×150mm×1.5mm and test its performance.

[0039] Example 6; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in sports equipment accessories.

[0040] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.04 g of isophorone diisocyanate, 0.0171 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.67 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.45 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) Pour the above-obtained reaction liquid into the surface mold of the yoga mat, and then dry and cure it at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer; cut the double dynamic bond self-healing polyurethane elastomer into a yoga mat of 300mm×150mm×1.5mm and test its performance.

[0041] Example 7; This embodiment provides a dual dynamic bond self-healing polyurethane elastomer, its preparation method, and its application in sports equipment accessories.

[0042] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.15 g of isophorone diisocyanate, 0.0175 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, add 0.94 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution, and react for 12 h to form hydrogen bond hard segments; add 0.34 g of 4,4'-diaminodiphenyl disulfide and 7 mL of N,N-dimethylacetamide solution to the hydrogen bond hard segment reaction system, and continue to react at this temperature for 12 h to obtain the reaction solution; (3) Pour the above-obtained reaction liquid into the surface mold of the yoga mat, and then dry and cure it at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer; cut the double dynamic bond self-healing polyurethane elastomer into a yoga mat of 300mm×150mm×1.5mm and test its performance.

[0043] Comparative Example 1; The only difference between the polyurethane elastomer of Comparative Example 1 and Example 2 is step (2). Step (2) is modified as follows: the above isocyanate-terminated prepolymer reaction system is cooled to 40°C, 0.67g of ethylenediamine and 7mL of N,N-dimethylacetamide solution are added, and the reaction is carried out for 12h to form hydrogen-bonded hard segments; 0.45g of 4,4'-diaminodiphenyl disulfide and 7mL of N,N-dimethylacetamide solution are added to the hydrogen-bonded hard segment reaction system, and the reaction is continued at this temperature for 12h to obtain the reaction solution; the remaining steps are the same as in Example 2.

[0044] Comparative Example 2; The only difference between the polyurethane elastomer of Comparative Example 1 and Example 2 is step (2). Step (2) is modified as follows: the above isocyanate-terminated prepolymer reaction system is cooled to 40°C, 0.67 g of isophthalic acid dihydrazide and 7 mL of N,N-dimethylacetamide solution are added, and the reaction is carried out for 12 h to form hydrogen-bonded hard segments; 0.45 g of 1,4-butanediol and 7 mL of N,N-dimethylacetamide solution are added to the hydrogen-bonded hard segment reaction system, and the reaction is continued at this temperature for 12 h to obtain the reaction solution; the remaining steps are the same as in Example 2.

[0045] Comparative Example 3; This comparative example aims to demonstrate that when using the exact same raw material ratio as in Example 2 of the present invention, if the core stepwise chain extension process is changed and a mixed chain extension method is adopted, the overall performance of the resulting material will decrease significantly.

[0046] The preparation process of the polyurethane elastomer includes the following steps: (1) 10.00 g of polytetrahydrofuran ether diol (Mn=2000) was degassed and dehydrated at 110 °C and -0.095 MPa vacuum for 0.5 h. Under a nitrogen atmosphere, 2.20 g of isophorone diisocyanate, 0.0173 g of dibutyltin dilaurate and 7 mL of N,N-dimethylacetamide solution were added and reacted at 80 °C for 3 h to obtain isocyanate-terminated prepolymer; (2) Cool the above isocyanate-terminated prepolymer reaction system to 40°C, dissolve 0.67 g of isophthalic acid dihydrazide and 0.45 g of 4,4'-diaminodiphenyl disulfide in 14 mL of N,N-dimethylacetamide, and then add this mixed solution to the prepolymer reaction system. Continue the reaction at this temperature for 12 h to obtain the reaction solution; (3) Pour the above-obtained reaction liquid into the surface mold of the yoga mat, and then dry and cure it at 80°C for 12 hours to obtain a double dynamic bond self-healing polyurethane elastomer; cut the double dynamic bond self-healing polyurethane elastomer into a yoga mat of 300mm×150mm×1.5mm and test its performance.

[0047] To more comprehensively verify the overall performance of the dual dynamic bond self-healing polyurethane elastomer described in this invention, supplementary performance tests were conducted on the samples of each embodiment. The specific methods and results are as follows: Temperature stability test (corresponding to Example 1) The polyurethane elastomer prepared in Example 1 and used in industrial pipeline seals was subjected to a temperature aging test.

[0048] The standard specimens were placed in constant temperature environments of -40℃ and 60℃ for 24 hours, then restored to room temperature (23±2℃) and their tensile strength was measured.

[0049] The results showed that the tensile strength retention rates of the samples were 92% and 88%, respectively. This data confirms that the material maintains excellent mechanical property stability over a wide temperature range of up to 100℃, which can meet the long-term use requirements of industrial pipeline seals under complex and variable temperature conditions.

[0050] Toughness, dynamic mechanical properties and practical flexibility tests (corresponding to Example 2) The polyurethane elastomer prepared in Example 2, suitable for sports equipment accessories, was subjected to in-depth mechanical characterization.

[0051] Toughness characterization: According to GB / T528-2009 standard, the polyurethane elastomer prepared in Example 2 was made into standard specimens for testing. The calculated fracture energy was 235.8 MJ / m³, indicating that the material can absorb a large amount of energy before fracture and has high impact resistance and tear resistance.

[0052] Dynamic thermomechanical analysis (DMA): Tests showed that the material's glass transition temperature was as low as -48°C, and its storage modulus remained stable at 1.2 GPa within the operating temperature range of 0°C to 70°C, indicating that the material has both good elasticity and shape retention capabilities over a wide temperature range.

[0053] Simulated use test: After the yoga mat sample was subjected to 100 consecutive tight rolls, no visible creases or damage were produced on its surface and structure.

[0054] Based on the above results, the material in Example 2 exhibits high toughness, excellent low-temperature elasticity, and resistance to repeated deformation, fully demonstrating its suitability for sports equipment such as yoga mats that need to withstand dynamic bending and complex deformation.

[0055] Fatigue resistance and barrier performance testing (corresponding to Example 4) The polyurethane elastomer film prepared in Example 4 was subjected to specific tests for flexible packaging applications. Folding fatigue resistance: Following the standard film folding fatigue test method, the sample was folded 180° back and forth. After 1000 cycles, no damage or cracks appeared, indicating that the film has excellent flexibility and fatigue life.

[0056] Moisture permeability test: According to GB / T1037 standard, the water vapor permeability of this film is as low as 0.8g / (m²·24h), showing excellent moisture barrier performance.

[0057] The above data shows that the film material prepared in Example 4 has both excellent resistance to repeated bending and effective water vapor barrier capabilities, and its comprehensive performance meets the dual requirements of high-end flexible packaging materials for durability and protection.

[0058] Mechanical property testing: According to the standard method of GB / T528-2009, the cured polyurethane elastomers of each embodiment and comparative example were made into standard specimens, and their tensile strength and elongation at break were tested using a universal testing machine. Self-healing performance test: According to the GB / T528-2009 method, the cured polyurethane elastomers of each embodiment and comparative example were made into standard specimens and conditioned for 24 hours in a standard environment of 23±2℃ and 50±5% relative humidity. The specimens were completely cut at the center of the gauge length and the two broken surfaces were joined together. The joined specimens were placed in an oven at 80±2℃ and left to stand for 12 hours, and then naturally cooled to room temperature. The tensile strength of the original specimens and the repaired specimens were tested using a universal testing machine at a tensile rate of 500 mm / min. The repair efficiency (%) = (repaired tensile strength / original tensile strength) × 100%. The specific results are shown in Table 1 below.

[0059] Table 1

[0060] As shown in Table 1, Example 1 achieved ultra-high tensile strength (62.8 MPa) while maintaining a repair efficiency of over 39%, indicating that the polyurethane elastomer of the present invention can be applied to industrial pipeline seals under this raw material ratio and achieve self-repair.

[0061] Example 2 showed excellent performance in terms of tensile strength (49.2 MPa) and elongation at break (1489%), while achieving a repair efficiency of 81.6%. This indicates that the polyurethane elastomer with this raw material ratio is very suitable for use in sports equipment accessories such as yoga mats, and can maintain high strength and self-healing ability while withstanding large deformations.

[0062] Example 3 achieved the best balance between tensile strength (32.4 MPa) and repair efficiency (90.3%), and had an extremely high elongation at break (1612%), with particularly outstanding overall performance. This indicates that the polyurethane elastomer with this raw material ratio can not only meet the application requirements of flexible packaging films, but also has good self-healing properties.

[0063] Example 4 achieved a repair efficiency of up to 98.1% while maintaining a tensile strength of 10.3 MPa, ensuring the basic structural integrity during use. This demonstrates that the polyurethane elastomer of the present invention, while pursuing extremely high repair performance, has not lost its strength when applied to flexible packaging films.

[0064] The strength and repair efficiency of Comparative Example 1 were significantly inferior to those of Example 2, demonstrating that isophthalic acid dihydrazide can improve the self-healing properties and tensile strength of polyurethane elastomers.

[0065] The repair efficiency of Comparative Example 2 was much lower than that of Example 2, demonstrating that 4,4'-diaminodiphenyl disulfide can improve the self-healing properties of polyurethane elastomers.

[0066] The performance of the hybrid chain extension synthesis process in Comparative Example 3 was significantly lower than that of Example 2, which used stepwise chain extension. This shows that the stepwise chain extension process, which first constructs hydrogen-bonded hard segments and then introduces disulfide-bonded soft segments, can achieve better tensile strength, elongation at break, and self-healing properties.

[0067] Figure 2 These are Fourier transform infrared (FTIR) spectra comparisons of the polyurethane elastomers prepared in Examples 1-4 of this invention, where PU-ID1 is Example 1, PU-ID2 is Example 2, PU-ID3 is Example 3, and PU-ID4 is Example 4; Figure 2 It can be seen that the characteristic NH absorption peak appears at about 3359 cm⁻¹, which belongs to the acylaminourea structure generated by the reaction of isophthalic dihydrazide and isocyanate. This structure is the basis for the formation of strong hydrogen bond hard segments. The characteristic C=O absorption peak appears at about 1710 cm⁻¹. The characteristic SS bond absorption peak appears at about 630 cm⁻¹, which belongs to the disulfide bond introduced by 4,4'-diaminodiphenyl disulfide. The spectral characterization confirms the successful construction of the target chemical structure.

[0068] Figure 3 The figures show the stress-strain curves of the polyurethane elastomers prepared in Examples 1 to 4 of the present invention, where PU-ID1 is Example 1, PU-ID2 is Example 2, PU-ID3 is Example 3, and PU-ID4 is Example 4. The dashed lines represent the test results of each example after repair at 80°C for 12 hours. like Figure 3 As shown, with the increase of the proportion of isophthalic acid dihydrazide in the formulation, the tensile strength of the curve increases significantly, while the elongation at break decreases accordingly; this demonstrates that by adjusting the ratio of IPDH to DTDA, the mechanical properties of the material can be continuously controlled over a wide range, making it suitable for different application scenarios ranging from high rigidity and high strength to high flexibility and ultra-high elongation.

[0069] Figure 4This is a schematic diagram showing the stress-strain curves and repair efficiency of the polyurethane elastomer in Example 2 of the present invention at different temperatures; Figure 4 It can be seen that the stress-strain curve of the polyurethane elastomer prepared in Example 2 of the present invention is closest to the original sample after repair at 80°C for 12 hours, and the repair efficiency reaches 81.6%.

[0070] Figure 5 This is a schematic diagram showing the weight changes of the polyurethane elastomers in Examples 1-4 of the present invention at different temperatures, wherein PU-ID1 is Example 1, PU-ID2 is Example 2, PU-ID3 is Example 3, and PU-ID4 is Example 4; Figure 5 It can be seen that the polyurethane elastomers of Examples 1 to 4 have excellent stability over a wide temperature range, which meets the temperature resistance requirements of the application scenarios.

[0071] 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 technical principles 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 dual-dynamic-knot self-healing polyurethane elastomer, characterized in that, The raw materials for preparing the self-repairing polyurethane elastomer include, in mass percentage: 74-76% of polyether polyol, 15.5-18% of diisocyanate, 1.67-7% of dihydrazide compound, and 2.1-6.7% of disulfide compound; The mass ratio of the dihydrazide compound to the disulfide compound is (0.25-3):1; The raw materials further include a catalyst; The mass of the catalyst is 0.1-0.15wt% of the total mass of the polyether polyol, diisocyanate, dihydrazide compound, and disulfide compound.

2. The dual-dynamic-knot self-healing polyurethane elastomer according to claim 1, wherein, The polyether polyol is polytetrahydrofuran ether diol.

3. The dual-dynamic-key self-healing polyurethane elastomer according to claim 1, wherein, The diisocyanate is isophorone diisocyanate.

4. The dual-dynamic-key self-healing polyurethane elastomer according to claim 1, wherein, The catalyst is dibutyltin dilaurate.

5. The dual-dynamic-key self-healing polyurethane elastomer according to claim 1, wherein, The dihydrazide compound is one or more of the following: isophthalic acid dihydrazide and adipic acid dihydrazide.

6. The dual-dynamic-key self-healing polyurethane elastomer according to claim 1, wherein, The disulfide compound is one or more of the following: 4,4'-diaminodiphenyl disulfide and bis(2-hydroxyethyl) disulfide.

7. A process for the preparation of a dual-dynamic-knot self-healing polyurethane elastomer as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: (1) After vacuum dehydration of the polyether polyol, the polyether polyol is reacted with diisocyanate and a catalyst in N,N-dimethylacetamide solution at 60-85℃ for 2-4h to obtain an isocyanate-terminated prepolymer; (2) The isocyanate-terminated prepolymer is cooled to 35-45℃, and an N,N-dimethylacetamide solution of dihydrazide compound is added, and reacted for 10-14h to form a hydrogen-bonded hard segment; at 35-45℃, an N,N-dimethylacetamide solution of disulfide compound is added to the reaction system of the hydrogen-bonded hard segment, and the reaction is continued for 10-14h to obtain a reaction liquid; (3) The reaction liquid obtained above is subjected to molding processing, and then dried and cured at 70-90℃ to obtain a dual-dynamic-bond self-repairing polyurethane elastomer.

8. Use of the dual-dynamic-bond self-repairing polyurethane elastomer according to any one of claims 1-6 in industrial pipeline seals, flexible packaging films, and sports equipment accessories.

Images