A high-strength, recyclable antibacterial polyurethane damping elastomer and its preparation method

Abstract

This invention relates to a high-strength, recyclable, antibacterial polyurethane damping elastomer and its preparation method, belonging to the field of polymer elastomer technology. The UPy-CS functional unit is obtained by grafting chitosan (CS) onto UPy-NCO, an isocyanate-terminated polymer synthesized from hexamethylene diisocyanate (HDI) and 2-ureido-4[1H]pyrimidinone. This functional unit is then introduced into a polyurethane system containing Diels-Alder dynamic covalent bonds in the main chain, resulting in an elastomer with excellent comprehensive properties. The material exhibits a tensile strength of up to 49.75 MPa, achieves efficient self-healing within 5 minutes at 50°C, and possesses both good closed-loop recyclability and antibacterial properties.

Description

Technical Field

[0001] This invention relates to a high-strength recyclable antibacterial polyurethane damping elastomer and its preparation method, belonging to the field of polymer elastomer technology. Background Technology

[0002] Polyurethane damping elastomers are crucial for solving vibration and noise problems, and are widely used in the protection of precision instruments, structural stability, and equipment life extension. With the rapid development of advanced fields such as soft robotics and high-end sports equipment, more stringent and diverse performance requirements are being placed on next-generation elastomers. An ideal elastomer not only needs to possess both high mechanical strength and high toughness to withstand complex loads, but also, based on the concept of sustainable development, recyclability has become an indispensable basic attribute. Furthermore, in applications with strict hygiene and safety requirements, such as wearable devices and medical assistive robots, the inherent antibacterial properties of elastomers are also crucial.

[0003] In recent years, dynamic networks constructed based on dynamic covalent bonds and supramolecular interactions have provided a new strategy for balancing high strength and damping. These networks can dissipate energy through reversible bond breaking and recombination, maintaining strength while continuously consuming energy and even possessing self-healing capabilities. However, their mechanical properties still fall short of high load-bearing requirements, their thermosetting structures make recycling difficult, and their functions are limited. Integrating multiple properties such as high strength, damping, recyclability, and antibacterial properties remains a major challenge in the field of elastomers. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a high-strength, recyclable, antibacterial polyurethane damping elastomer and its preparation method. The UPy-CS functional unit is obtained by grafting chitosan (CS) onto an isocyanate-terminated UPy-NCO synthesized from hexamethylene diisocyanate (HDI) and 2-ureido-4[1H]pyrimidinone. This functional unit is then introduced into a polyurethane system with Diels-Alder dynamic covalent bonds in the main chain, resulting in an elastomer with excellent comprehensive properties. This material exhibits a tensile strength of up to 49.75 MPa, achieves efficient self-healing within 5 minutes at 50°C, and possesses both good closed-loop recyclability and antibacterial properties.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] A high-strength, recyclable, antibacterial polyurethane damping elastomer, with the following composition and mass fraction of each raw material as 100% of the total mass of the raw materials used to prepare the elastomer:

[0007] Polydiol 60%~70%; Diisocyanate 10%~20%; furfurylamine 4%~6%; Bismaleimide 10%~14%; UPy-CS 0.1%~3%; The UPy-CS is obtained by grafting chitosan (CS) onto UPy-NCO, and the structure of UPy-NCO is as follows: .

[0008] Preferably, the UPy-CS is prepared by the following method: UPy-NCO is dissolved in dimethylacetamide (DMAc), then chitosan powder is added, and the mixture is reacted at 40~50℃ for more than 24 hours. After the reaction is completed, the mixture is filtered and dried to obtain UPy-CS.

[0009] Preferably, the weight-average molecular weight of the chitosan is 30-100 kDa.

[0010] Preferably, the mass ratio of chitosan to UPy-NCO is 1~2:1.

[0011] Preferably, the mass fraction of the UPy-CS is 0.5% to 1%.

[0012] Preferably, the polydiol is one or more of polypropylene glycol (PPG), polybutylene glycol (PTMEG), and polyethylene glycol (PEG). More preferably, the polydiol has a molecular weight of 1800-2050 and requires dehydration treatment before use.

[0013] Preferably, the diisocyanate is one or more of diphenylmethane diisocyanate (MDI), toluene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0014] A method for preparing a high-strength, recyclable antibacterial polyurethane damping elastomer according to the present invention, comprising the following steps: (1) Under a protective gas atmosphere, polydiol and diisocyanate are prepolymerized at 75~85℃ for 3~4h to obtain isocyanate-terminated prepolymer; (2) Under a protective gas atmosphere, the prepolymer is added to the solvent dimethylacetamide (DMAc), and then furfurylamine is added. The reaction is carried out at 15~30℃ for 3~3.5h. Then the temperature is raised to 60~65℃, bismaleimide is added, and after the chain extension reaction is carried out for 1~3h, UPy-CS is added, and the reaction is continued for 20~23h. (3) After the reaction is completed, the solvent is removed by vacuum degassing and then heated to evaporate, resulting in a high-strength recyclable antibacterial polyurethane damping elastomer.

[0015] Preferably, in step (3), the solvent is degassed under vacuum for 30-40 minutes and then heated to 80-90°C to evaporate.

[0016] Beneficial effects In this invention, UPy-CS is used as a functional unit, reacting with the -NCO groups at the molecular chain ends to attach to them. Free UPy-CS interacts with the UPy-CS on the molecular chain through multiple hydrogen bonds between UPy groups, increasing the hydrogen bond density of the PU-UPy-CS system. This significantly improves the mechanical strength of the elastomer while maintaining the elongation at break. A unique "multi-scale energy dissipation network" is constructed through the synergy of dynamic Diels-Alder covalent bonds and quadruple hydrogen bonds, achieving a balance between high strength and damping. The dynamic Diels-Alder covalent bonds and multiple hydrogen bonds within the elastomer enable the repair and reconstruction of the macroscopic network, resulting in rapid local energy dissipation. In particular, the strain-induced crystallization effect triggered by UPy-CS significantly increases the tensile strength to 49.75 MPa while maintaining an elongation of 1100%, and keeps the effective damping temperature range stable at 40°C.

[0017] Secondly, the elastomer exhibits sustainability, achieving rapid self-repair within 5 minutes at 50°C, restoring mechanical properties and extending service life. Based on the thermally reversible properties of the dynamic network, the elastomer can be recycled and reprocessed in a closed loop using solvents. After three recycling cycles, the mechanical properties retain more than 75%, demonstrating excellent recyclability. Simultaneously, by introducing UPy-CS functional units, the material is endowed with intrinsic, durable, and safe antibacterial properties, making it suitable for hygiene-sensitive fields such as wearable devices and medical applications.

[0018] In this invention, the key component, furfurylamine, is derived from biomass resources, and chitosan is a natural polymer, embodying the environmentally friendly design concept of elastomers. This invention not only successfully integrates multiple properties such as high strength, damping, recyclability, and antibacterial properties, but also provides an innovative solution for developing advanced "functionally integrated" materials for next-generation intelligent equipment, flexible electronics, and biomedical devices. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of the elastomer in Example 1.

[0020] Figure 2 The diagram shows the mechanical properties of the elastomers in the examples and comparative examples.

[0021] Figure 3 The diagram shows the damping performance of the elastomer in the examples and comparative examples.

[0022] Figure 4 The diagram shows the self-healing performance of the elastomers in Example 3 and Comparative Example 1.

[0023] Figure 5 The images show the mechanical and infrared spectra of the elastomers in Example 3 and Comparative Example 1 after multiple recycling processes.

[0024] Figure 6 The diagram shows the antibacterial properties of the elastomers in Example 3 and Comparative Example 1. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] In the following examples and comparative examples, UPy-CS was prepared by the following method: UPy-NCO was dissolved in dimethylacetamide (DMAc), then chitosan powder (weight-average molecular weight of 50 kDa) was added, and the mixture was reacted at 40°C for 24 h. After the reaction was completed, the mixture was filtered and dried under vacuum to obtain UPy-CS, wherein m(CS):m(UPy) = 1:1. The reaction equation is as follows: .

[0027] Example 1 like Figure 1 As shown, a method for preparing a high-strength, recyclable antibacterial polyurethane damping elastomer includes the following steps: (1) Under nitrogen protection, dehydrated PTMEG2000 (10g) and MDI (2.5g) were reacted at 80℃ for 3h with a -NCO:-OH molar ratio of 2:1 to obtain a prepolymer; (2) Under nitrogen protection, the prepolymer was cooled to room temperature, DMAc (10 mL) was added to reduce the viscosity of the system, and then furfurylamine (0.75 mL) was added. The reaction was carried out at room temperature for 3 h, and then the temperature was raised to 60 °C. Bismaleimide (1.75 g) was added to react with furfurylamine to open the ring and extend the chain. After reacting for 1 h, UPy-CS functional unit was added (the amount of UPy-CS added was 0.1% of the total mass of PTMEG2000, MDI, furfurylamine, bismaleimide and UPy-CS), and the reaction was continued for 23 h. (3) After the reaction is complete, vacuum degassing is performed for 30 min, solvent is evaporated at 80℃, and finally polyurethane elastomer is obtained, which is denoted as PU-UPy-CS1.

[0028] Example 2 In this embodiment, the amount of UPy-CS added is 0.5% of the total mass of PTMEG2000, MDI, furfuralamine, bismaleimide and UPy-CS, and the rest is the same as in Example 1. The resulting elastomer is denoted as PU-UPy-CS2.

[0029] Example 3 In this embodiment, the amount of UPy-CS added is 0.8% of the total mass of PTMEG2000, MDI, furfuralamine, bismaleimide and UPy-CS, and the rest is the same as in Example 1. The resulting elastomer is denoted as PU-UPy-CS3.

[0030] Example 4 In this embodiment, the amount of UPy-CS added is 1% of the total mass of PTMEG2000, MDI, furfuralamine, bismaleimide and UPy-CS, and the rest is the same as in Example 1. The resulting elastomer is denoted as PU-UPy-CS4.

[0031] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that UPy-CS is not added.

[0032] (1) Under nitrogen protection, dehydrated PTMEG2000 (10g) and MDI (2.5g) were reacted at 80℃ for 3h with a -NCO:-OH molar ratio of 2:1 to obtain a prepolymer; (2) Under nitrogen protection, the prepolymer was cooled to room temperature, DMAc (10 mL) was added to reduce the viscosity of the system, and then furfurylamine (0.75 mL) was added. The reaction was carried out at room temperature for 3 h, and then the temperature was raised to 60 °C. Bismaleimide (1.75 g) was added to react with furfurylamine to open the ring and extend the chain. The reaction was carried out for 24 h. (3) After the reaction is complete, vacuum degassing is performed for 30 minutes, and the solvent is evaporated at 80°C to obtain polyurethane elastomer, denoted as DAPU.

[0033] Comparative Example 2 The difference between this comparative example and Example 3 is that chitosan was added.

[0034] (1) Under nitrogen protection, dehydrated PTMEG2000 (10g) and MDI (2.5g) were reacted at 80℃ for 3h with a -NCO:-OH molar ratio of 2:1 to obtain a prepolymer; (2) Under nitrogen protection, the prepolymer was cooled to room temperature, DMAc (10 mL) was added to reduce the viscosity of the system, and then furfurylamine (0.75 mL) was added. The reaction was carried out at room temperature for 3 h, and then the temperature was raised to 60 °C. Bismaleimide (1.75 g) was added to react with furfurylamine to open the ring and extend the chain. After reacting for 1 h, chitosan was added (the amount of chitosan added was 0.8% of the total mass of PTMEG2000, MDI, furfurylamine, bismaleimide and chitosan), and the reaction was continued for 23 h. (3) After the reaction is complete, vacuum degassing is performed for 30 minutes, and the solvent is evaporated at 80°C to obtain polyurethane elastomer, denoted as PU-CS.

[0035] Comparative Example 3 The difference between this comparative example and Example 1 is that it does not use DA dynamic chain extender and does not add UPy-CS functional unit.

[0036] (1) Under nitrogen protection, dehydrated PTMEG2000 (10g) and MDI (2.5g) were reacted at 80℃ for 3h with a -NCO:-OH molar ratio of 2:1 to obtain a prepolymer; (2) Under nitrogen protection, the prepolymer was added to DMAc (10 mL), and then 1,4-butanediol was added. The reaction was carried out at 80 °C for 4 h. After the reaction was completed, the prepolymer was degassed under vacuum for 30 min, and the solvent was evaporated at 80 °C. Finally, polyurethane elastomer was obtained, which was denoted as PU.

[0037] Comparative Example 4 The difference between this comparative example and Example 3 is that the UPy-CS functional unit was added after reacting for 6 hours following the addition of bismaleimide. The rest is the same as in Example 3. The resulting polyurethane elastomer is denoted as PU-UPy-CS5.

[0038] Comparative Example 5 The difference between this comparative example and Example 3 is that the UPy-CS functional unit was added after reacting with bismaleimide for 24 hours. Otherwise, it is the same as Example 3. The resulting polyurethane elastomer is denoted as PU-UPy-CS6.

[0039] The mechanical properties of each embodiment and comparative example were tested according to the standard GB / T 1040.2-2022, and the results are as follows: Figure 2 As shown, in Example 3, PU-UPy-CS3 exhibits the highest tensile strength, reaching 49.75 MPa, while maintaining a high elongation at break of 1100%. In Example 4, PU-UPy-CS4 achieves a strength of 43.61 MPa and an elongation at break of 1192.63%. In Example 2, PU-UPy-CS2 achieves a strength of 42.16 MPa and an elongation at break of 997.29%. In Example 1, PU-UPy-CS1 has a strength of 39.97 MPa and an elongation at break of 1200.77%. In Comparative Example 1, without the addition of the UPy-CS functional unit, the strength of DAPU was 26.68 MPa, significantly lower than that of the examples. In Comparative Example 2, the strength of PU-CS was 31.85 MPa. In Comparative Example 3, without the use of DA dynamic covalent chain extender and UPy-CS functional unit, the strength of PU was 10.34 MPa. In Comparative Example 4, the strength of PU-UPy-CS5 was 30.573 MPa, with an elongation at break of 1032.56%. In Comparative Example 5, the strength of PU-UPy-CS6 was 33.68 MPa, with an elongation at break of 884.92%, significantly lower than that of the examples. These results demonstrate that the combined effect of DA dynamic covalent bonds and multiple hydrogen bonds significantly improves the mechanical properties of polyurethane elastomers.

[0040] The damping performance of each embodiment and comparative example was tested using a Mettler DMA / SDTA861e instrument from Switzerland at temperatures ranging from -80°C to 80°C. The results are as follows: Figure 3As shown, the effective damping temperature range of Comparative Example 3 is 26℃, while the others are all 40℃. This indicates that the presence of DA bonds broadens the effective damping temperature range of polyurethane. Each embodiment significantly improves mechanical properties while ensuring a stable damping temperature range, providing a new approach to resolving the contradiction between damping and mechanical properties.

[0041] The self-healing behavior of Example 3 and Comparative Example 1 was observed using an optical microscope, and the results are as follows: Figure 4 As shown, cracks were cut into the surface of the samples, a small amount of solvent was added to the cracks, and the samples were repaired at 50°C for 2 minutes. The cracks in both groups of samples showed significant reduction in size. After being left for another 3 minutes, the crack in Example 3 almost disappeared, while the crack in Comparative Example 1 became even shallower. The above results clearly demonstrate that, thanks to the rich dynamic hydrogen bond network and DA reversible covalent bonds within the material, the examples possess significant self-healing properties.

[0042] Further evaluation of the recovery performance of the embodiments yielded the following results: Figure 5 As shown, Example 3 was cut into fragments, then completely immersed in DMAc solvent to dissolve them, and then the solvent was evaporated by heating at 80°C, ultimately achieving closed-loop recovery of the example. After three cycles of recovery, the tensile strength and elongation at break of Example 3 showed only a limited decrease, and the recovery efficiency remained stable above 75% each time. Chemical structural stability analysis further confirmed that the solvent recovery process did not change the chemical composition of the material, and the characteristic peak positions in the Fourier transform infrared spectrum remained consistent, indicating that its dynamic bond network structure was completely preserved.

[0043] Example 3 and Comparative Example 1 were selected for antibacterial testing. The inhibitory effects of the elastomer on Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) were evaluated using the inhibition zone method and plate count method. The samples were circular discs with a diameter of 6 mm and a thickness of 1.2 mm, which were sterilized by ultraviolet light before use. The results are as follows... Figure 6 As shown, neither Example 3 nor Comparative Example 1 formed a significant inhibition zone in the *E. coli* group, while both produced an inhibition zone of approximately 2 mm in the *Staphylococcus aureus* group, confirming a significant interfacial antibacterial effect against Gram-positive bacteria. Plate count further quantified the antibacterial efficiency. After 24 hours of mixed culture of the elastomer and bacterial suspension, no viable colonies of *Staphylococcus aureus* were found in either group, achieving a 100% kill rate. *E. coli* showed 64 CFU remaining in Comparative Example 1 (93.75% kill rate), while Example 3 showed only 34 CFU remaining (96.88% kill rate). This high performance stems from the protonated amino groups of chitosan disrupting bacterial membrane integrity and the multiple hydrogen bonds enhancing chitosan dispersibility, synergistically enhancing antibacterial efficiency.

[0044] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A high-strength, recyclable antibacterial polyurethane damping elastomer, characterized in that: Based on the total mass of the raw materials used to prepare the elastomer being 100%, the composition and mass fraction of each raw material are as follows: Polydiol 60%~70%; Diisocyanate 10%~20%; furfurylamine 4%~6%; Bismaleimide 10%~14%; UPy-CS 0.1%~3%; The UPy-CS is obtained by grafting chitosan onto UPy-NCO, and the structure of UPy-NCO is as follows: .

2. The high-strength recyclable antibacterial polyurethane damping elastomer according to claim 1, characterized in that: The UPy-CS was prepared by the following method: UPy-NCO was dissolved in dimethylacetamide, then chitosan powder was added, and the mixture was reacted at 40~50℃ for more than 24 hours. After the reaction was completed, the mixture was filtered and dried to obtain UPy-CS.

3. A high-strength, recyclable antibacterial polyurethane damping elastomer according to claim 1 or 2, characterized in that: The weight-average molecular weight of the chitosan is 30~100 kDa.

4. A high-strength, recyclable antibacterial polyurethane damping elastomer according to claim 1 or 2, characterized in that: The mass ratio of chitosan to UPy-NCO is 1~2:

1.

5. The high-strength recyclable antibacterial polyurethane damping elastomer according to claim 1, characterized in that: The mass fraction of UPy-CS is 0.5% to 1%.

6. The high-strength recyclable antibacterial polyurethane damping elastomer according to claim 1, characterized in that: The polydiol is one or more of polypropylene glycol, polybutylene glycol, and polyethylene glycol.

7. A high-strength, recyclable antibacterial polyurethane damping elastomer according to claim 1 or 6, characterized in that: The molecular weight of the polydiol is 1800~2050.

8. The high-strength recyclable antibacterial polyurethane damping elastomer according to claim 1, characterized in that: The diisocyanate is one or more of diphenylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

9. A method for preparing a high-strength, recyclable antibacterial polyurethane damping elastomer according to any one of claims 1 to 8, characterized in that: The method steps include: (1) Under a protective gas atmosphere, polydiol and diisocyanate are prepolymerized at 75~85℃ for 3~4h to obtain isocyanate-terminated prepolymer; (2) Under a protective gas atmosphere, the prepolymer is added to the solvent dimethylacetamide, and then furfurylamine is added. The reaction is carried out at 15~30℃ for 3~3.5h. Then the temperature is raised to 60~65℃, bismaleimide is added, and after the chain extension reaction is carried out for 1~3h, UPy-CS is added and the reaction is continued for 20~23h. (3) After the reaction is completed, the solvent is removed by vacuum degassing and then heated to evaporate, resulting in a high-strength recyclable antibacterial polyurethane damping elastomer.

10. The method for preparing a high-strength, recyclable antibacterial polyurethane damping elastomer according to claim 9, characterized in that: In step (3), vacuum degassing is performed for 30-40 minutes, and the solvent is evaporated by heating to 80-90°C.

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