Functionalized graphene reinforced polyurethane nanocomposites, methods of making and applications thereof

Abstract

The application relates to the technical field of high-molecular composite materials and gas barrier materials, and particularly discloses a functionalized graphene reinforced polyurethane nanocomposite material as well as a preparation method and application thereof. The nanocomposite material comprises a polyurethane matrix containing Diels-Alder dynamic covalent bonds and functionalized graphene nanofillers dispersed in the polyurethane matrix; wherein the functionalized graphene surface contains active groups capable of chemically reacting with the polyurethane matrix; the dynamic Diels-Alder bonds are simultaneously present in the polyurethane network and the dynamic Diels-Alder bonds are simultaneously present at the filler-matrix interface in the composite material. By simultaneously introducing the dynamic Diels-Alder bonds in the polyurethane network and the filler-matrix interface, the self-repairing capability of the material after damage is realized, and the mechanical properties and hydrogen barrier properties of the material are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials and gas barrier materials, and particularly to a functionalized graphene-reinforced polyurethane nanocomposite material, its preparation method, and its application. Background Technology

[0002] With the development of hydrogen energy technology, the demand for high-performance hydrogen storage and transportation materials is increasing. Polymer materials, due to their light weight and good processability, have been widely used in the linings and related sealing structures of Type IV hydrogen storage cylinders. However, traditional polymer materials still face the following problems in actual service: (1) Hydrogen is easily permeable: Hydrogen molecules are small in size and have strong diffusion ability, which makes it difficult for polymer materials to achieve long-term stable gas barrier performance; (2) Irreversible damage: Microcracks or macroscopic damage generated during service will significantly accelerate gas leakage, while traditional materials lack effective self-healing capabilities; (3) Difficulty in performance coupling: Existing studies usually optimize mechanical properties, barrier properties or self-healing properties separately, making it difficult to achieve synergistic improvement of the three properties in the same material system; (4) Insufficient interfacial interaction: Although the introduction of nanofillers can improve the barrier performance, the interfacial interaction between the filler and the matrix is ​​weak, which limits the effect of stress transmission and diffusion path regulation.

[0003] In recent years, self-healing polymers based on dynamic covalent bonds (such as the Diels-Alder system) have provided new ideas for solving material damage problems. However, most studies only focus on the dynamic behavior inside the matrix and ignore the dynamic regulation effect of the filler-matrix interface, resulting in limited improvement in overall performance.

[0004] Therefore, there is an urgent need to develop a novel composite material system that can introduce dynamic structures at both the matrix and interface levels to achieve synergistic optimization of self-healing, mechanical reinforcement, and hydrogen barrier properties. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a functionalized graphene-reinforced polyurethane nanocomposite material, which achieves synergistic improvement in self-healing properties, mechanical properties, and hydrogen barrier properties by simultaneously introducing dynamic Diels-Alder bonds into the polyurethane matrix and the filler-matrix interface, as well as its preparation method and application.

[0006] This invention is achieved through the following technical solution: A functionalized graphene-reinforced polyurethane nanocomposite material is characterized in that: the composite material comprises a polyurethane matrix containing Diels-Alder dynamic covalent bonds, and functionalized graphene nanofillers dispersed in the polyurethane matrix; wherein the surface of the functionalized graphene contains active groups capable of chemically reacting with the polyurethane matrix, thereby forming Diels-Alder dynamic covalent bonds at the interface between the nanofiller and the matrix.

[0007] This invention develops a novel composite material system that can simultaneously introduce dynamic covalent bonds in the matrix and interface. The composite material contains dynamic Diels-Alder bonds located in the polyurethane network and dynamic Diels-Alder bonds located at the filler-matrix interface to construct a dynamic network structure in which the matrix and interface work together to achieve synergistic optimization of self-healing, mechanical reinforcement and hydrogen barrier properties.

[0008] A more preferred technical solution of the present invention is as follows: The functionalized graphene is a graphene oxide that has been surface-modified by a compound containing a furan group.

[0009] The functionalized graphene has a mass fraction of 0.1-10% of the polyurethane matrix.

[0010] The composite structure of this invention constructs a dynamic network structure of "matrix-interface synergy". Functionalized graphene forms a confined interface region in the matrix, thereby inhibiting the cooperative movement of polymer chain segments and restricting the diffusion of hydrogen in the interface region, resulting in a highly tortuous gas diffusion path.

[0011] The dynamic Diels-Alder bond of this invention is formed by a reversible reaction between furan groups and maleimide groups. After mechanical damage, the composite material can achieve structural repair and restore its mechanical properties under heating conditions.

[0012] The preparation method of the above-mentioned functionalized graphene-reinforced polyurethane nanocomposite material includes the following steps: (1) Graphene oxide is uniformly dispersed in water or N,N-dimethylformamide (DMF), and then furfurylamine is added to modify the graphene oxide to introduce furan rings on the surface of the graphene oxide to obtain functionalized graphene. (2) Polyurethane containing dynamic Diels-Alder bonds was synthesized by using polypropylene glycol, isophorone diisocyanate, furfurylamine and 4,4'-bismaleimide diphenylmethane. (3) Disperse the functionalized graphene in the polyurethane obtained in step (2); (4) The nanocomposite material is obtained by curing.

[0013] More preferably, in step (1), the concentration of graphene oxide in water or N,N-dimethylformamide is 0.1-30 mg / mL, the mass ratio of graphene oxide to furfurylamide is 1:1-20, and furfurylamide and graphene oxide are ultrasonically dispersed in water or N,N-dimethylformamide, and then reacted at 100°C for 1-20 h to complete the modification.

[0014] More preferably, the concentration of graphene oxide in water or N,N-dimethylformamide is 2 mg / mL, the mass ratio of graphene oxide to furfurylamide is 1:5, and the furfurylamide and graphene oxide are ultrasonically dispersed or mechanically stirred in water or N,N-dimethylformamide, and then reacted at 100°C for 12 h.

[0015] More preferably, in step (2), polypropylene glycol and isophorone diisocyanate are mixed evenly, and dibutyltin dilaurate is added as a catalyst. The mixture is stirred and reacted for 1 h under a nitrogen atmosphere at 75 °C. Then, furfurylamine is dissolved in DMF and slowly added to the system. The mixture is stirred and reacted for another 1 h. Then, 4,4'-bismaleimide diphenylmethane is added and the mixture is stirred and reacted for another 4 h at 75 °C. The molar ratio of polypropylene glycol, isophorone diisocyanate, furfurylamine, and 4,4'-bismaleimide diphenylmethane is 1:2:2:2.

[0016] More preferably, in step (3), the functionalized graphene is mechanically stirred at 75°C and 50-500 rpm / min for 24 hours to achieve uniform dispersion in polyurethane; preferably, the mass fraction of the functionalized graphene is 0.1-5% of the polyurethane matrix.

[0017] More preferably, in step (4), the curing process is to spray or coat the sample surface, or to place the mixture in a mold and cast it into shape, and then dry it at 60°C for 48 hours. In the existing technology, most studies only introduce dynamic covalent bonds in the matrix, while dynamic covalent bonds at the interface are missing; even if a few studies introduce dynamic covalent bonds in the matrix and interface, they only study the self-healing behavior of the material and do not involve application aspects, such as hydrogen barrier performance.

[0018] The present invention also discloses the application of the above-mentioned functionalized graphene-reinforced polyurethane nanocomposite material as a coating material. Specifically, the coating material is applied to the surface of the substrate by spraying.

[0019] More preferably, the base layer is a polyamide material, a polyolefin material, or a polyester material.

[0020] Compared with the prior art, the present invention has the following advantages: (1) Excellent self-healing performance: After the material is cut or damaged, it can reconstruct its structure through dynamic DA bonds and restore its structural integrity; (2) Significantly improved mechanical properties: After the introduction of functionalized graphene, the tensile strength is significantly improved while maintaining good ductility. Moreover, the tensile strength of the repaired graphene is almost back to the original level and the toughness can exceed the original data. (3) Significantly enhanced hydrogen barrier performance: The hydrogen permeability coefficient is significantly reduced and remains at a low level after repair; (4) Clear interface regulation mechanism: By forming a restricted interface region through dynamic interface bonding, the cooperative movement of polymer chain segments is suppressed, thereby increasing diffusion resistance; (5) Synergistic enhancement of multiple performances: Achieving unified control of self-repair, mechanical enhancement and hydrogen barrier performance.

[0021] This invention enables the material to self-repair after damage by simultaneously introducing dynamic Diels-Alder bonds into the polyurethane network and the filler-matrix interface, and significantly improves its mechanical properties and hydrogen barrier properties. Attached Figure Description

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] Figure 1 This is a comparison diagram of the macroscopic sample before and after self-healing according to the present invention; Among them, (a) and (b) are comparison pictures of the tensile sample before and after repair, (c) is a picture of the tensile sample after repair and in use, and (d) and (e) are comparison pictures of the hydrogen barrier sample before and after repair. Figure 2 These are polarized light microscope comparison images of the composite material before and after cutting and repair according to the present invention; Figure 3 This is a schematic diagram of the composite material spraying implementation and samples before and after spraying according to the present invention; Figure 4 A comparison chart of tensile strength and Young's modulus of pure polyurethane materials and their composites; Figure 5 A comparison chart of the elongation at break and toughness of pure polyurethane materials and their composites; Figure 6 Stress-strain curves of pure polyurethane materials and their composites before and after repair; Figure 7 A comparison chart of the repair efficiency of pure polyurethane materials and their composites under different mechanical properties; Figure 8 A comparison chart of hydrogen permeability coefficients for pure polyurethane materials and their composites; Figure 9 This is a schematic diagram of the diffusion mechanism of the composite material of the present invention; Figure 10 Comparison of hydrogen permeability coefficients before and after repair using pure polyurethane materials and their composites; Figure 11 A comparison chart of hydrogen permeability coefficients for polyurethane 6 substrate material and sprayed samples. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Example 1: A functionalized graphene-reinforced polyurethane nanocomposite material A polyurethane matrix (PU-DA) containing Diels-Alder bonds was prepared, and functionalized graphene (fGO) was added to the system at a mass fraction of 5 wt%. The composite material was prepared by solution blending and in-situ reaction.

[0027] The composite material underwent performance testing, and the test results showed that: (1) The tensile strength increased from 5.6 MPa to 9.8 MPa; (2) The hydrogen permeability coefficient decreased by approximately 64%; (3) The material strength was basically restored after cutting and repair, and the toughness exceeded the original level; (4) It still maintains a significant advantage in hydrogen barrier after repair.

[0028] The tensile test used a dumbbell-shaped specimen of type 5A according to ISO 527-2 standard, and the tensile speed was set to 50 mm·min. -1 For the self-healing tensile test, the specimen was first heat-treated at 130°C for 10 min to activate the reverse Diels-Alder reaction, and then repaired at 60°C for 24 h to promote the reformation of Diels-Alder bonds.

[0029] The hydrogen permeability test temperature was 23℃, and the hydrogen test pressure was 0.1 MPa. The hydrogen permeability coefficient was determined under steady-state conditions. Samples used for the self-healing permeability test underwent the same treatment process as those used for tensile repair before testing.

[0030] Macroscopic sample images such as Figure 1 The restored microscopic images are as follows Figure 2 .

[0031] Some of the data is illustrated in the attached figures; the following are the specific data obtained from the tests.

[0032] Table 1 Comparison of mechanical properties of pure polyurethane and its composites

[0033] pass Figure 4 , Figure 5 As can be seen from the comparison in Table 1, the 5wt% functionalized graphene-reinforced polyurethane nanocomposite material has the highest tensile strength, while retaining good elongation at break and toughness, indicating the importance of filler doping for improving the mechanical properties of polyurethane.

[0034] Table 2 Comparison of mechanical properties of polyurethane reinforced with graphene oxide and functionalized graphene

[0035] As shown in Table 2, graphene oxide modification significantly improves the mechanical properties of the composite material. At the same concentration, without modification, the mechanical properties of the material deteriorate significantly, even falling below those of pure polyurethane. This difference primarily stems from the formation of dynamic Diels-Alder interfacial covalent bonds between functionalized graphene and polyurethane, which facilitates stress transfer and reduces microcrack formation. This comparative analysis highlights the importance of functionalized graphene.

[0036] Table 3 Comparison of mechanical properties of pure polyurethane and its composites before and after repair.

[0037] Table 4 Repair efficiency of pure polyurethane and its composites under different mechanical properties

[0038] Combination Figure 6 and Table 3, Figure 7 As shown in Table 4, both pure polyurethane and its composites can achieve high tensile strength repair efficiency after cutting and repair. Among them, the elongation at break and toughness of the composites are significantly higher than those of pure polyurethane, and even exceed the data of the original sample. This indicates that the dynamic Diels-Alder interface covalent bonds have an extremely obvious advantage in maintaining the long-term mechanical properties of the material.

[0039] Table 5 Normalized hydrogen permeability coefficient of pure polyurethane and its composites

[0040] Table 6 Comparison of barrier enhancement factors before and after repair of pure polyurethane and its composites

[0041] from Figure 8 As can be seen from Table 5, the composite material has lower hydrogen permeability and a barrier enhancement factor of 2.74, demonstrating excellent barrier performance. Figure 10 Table 6 shows that the composite material can still maintain a barrier enhancement factor of 1.98 after repair, indicating that the double Diels-Alder covalent bonds introduced at the matrix and interface can repair the barrier pathway.

[0042] Table 7 Hydrogen permeability coefficient of coating systems based on polyamide 6

[0043] Figure 11 The data in Table 7 show that the polyurethane nanocomposite material prepared by this invention can significantly reduce the hydrogen permeability coefficient of the substrate, and has important engineering application value.

[0044] Example 2: Preparation method of functionalized graphene-reinforced polyurethane nanocomposite materials The preparation method of this embodiment includes the following steps: (1) 0.1676 g of graphene oxide was dispersed in 50 mL of deionized water, 0.838 g of furfural was added, and then the mixture was stirred at 200 rpm and reacted at 100 °C for 12 hours to introduce furan rings on the surface of graphene oxide to obtain functionalized graphene. (2) 10g of polypropylene glycol 2000 and 2.22g of isophorone diisocyanate were mixed evenly, and 3 drops of dibutyltin dilaurate were added as a catalyst. The mixture was stirred at 75°C under a nitrogen atmosphere for 1h. Then, 0.96g of furfurylamine dissolved in 10mL of DMF was slowly added to the system, and the mixture was stirred for another 1h to ensure a complete reaction. Next, 3.58g of 4,4'-bismaleimide diphenylmethane was added, and the mixture was stirred at 75°C for another 24h to obtain a polyurethane containing dynamic Diels-Alder bonds. (3) Add 0.1676g of functionalized graphene according to the ratio of 1wt% of polyurethane, stir mechanically at 100rpm until uniform, and continue to react at 75℃ for 24h to obtain self-healing composite material. (4) The polyurethane composite material mixture obtained in step (3) is poured into a mold and baked at 60°C for 48 hours to completely remove DMF from the system. At this time, the mixture becomes a solid nanocomposite material.

[0045] Example 3: Preparation method of functionalized graphene-reinforced polyurethane nanocomposite materials The preparation method of this embodiment includes the following steps: (1) 0.6704 g of graphene oxide was dispersed in 100 mL of DMF, 3.352 g of furfural was added, and then the mixture was stirred at 300 rpm and reacted at 100 °C for 12 hours to introduce furan rings on the surface of graphene oxide to obtain functionalized graphene. (2) 20g of polypropylene glycol 2000 and 4.44g of isophorone diisocyanate were mixed evenly, and 3 drops of dibutyltin dilaurate were added as a catalyst. The mixture was stirred at 75°C under a nitrogen atmosphere for 1h. Then, 1.92g of furfurylamine dissolved in 10mL of DMF was slowly added to the system, and the mixture was stirred for another 1h to ensure complete reaction. Next, 7.16g of 4,4'-bismaleimide diphenylmethane was added, and the mixture was stirred at 75°C for another 24h to obtain a polyurethane containing dynamic Diels-Alder bonds. (3) According to the ratio of functionalized graphene to polyurethane 2wt%, add 0.6704g of functionalized graphene, disperse the functionalized graphene in 80ml of DMF and ultrasonically disperse it evenly, then add it to the polyurethane solution obtained in step (2), mechanically stir it evenly at 300rpm, and continue to react at 75℃ for 24h to obtain self-healing composite material. (4) The polyurethane composite material mixture obtained in step (3) is poured into a mold and baked at 60°C for 48 hours to completely remove DMF from the system. At this time, the mixture becomes a solid nanocomposite material.

[0046] Example 4: Preparation method of functionalized graphene-reinforced polyurethane nanocomposite materials The preparation method of this embodiment includes the following steps: (1) 2.514 g of graphene oxide was dispersed in 200 mL of deionized water, 12.57 g of furfural was added, and then the mixture was stirred at 500 rpm and reacted at 100 °C for 12 hours to introduce furan rings on the surface of graphene oxide to obtain functionalized graphene. (2) 30g of polypropylene glycol 2000 and 6.66g of isophorone diisocyanate were mixed evenly, and 3 drops of dibutyltin dilaurate were added as a catalyst. The mixture was stirred at 75°C under a nitrogen atmosphere for 1 h. Then, 2.88g of furfurylamine dissolved in 30mL of DMF was slowly added to the system, and the mixture was stirred for another 1 h to ensure a complete reaction. Next, 10.74g of 4,4'-bismaleimide diphenylmethane was added, and the mixture was stirred at 75°C for another 24 h to obtain a polyurethane containing dynamic Diels-Alder bonds. (3) According to the ratio of 5wt% of polyurethane, 2.514g of functionalized graphene was added. The functionalized graphene was dispersed in 150mL of DMF and ultrasonically dispersed evenly. Then it was added to the polyurethane solution obtained in step (2). After being mechanically stirred evenly at 500rpm, the reaction was continued at 75℃ for 24h to obtain the self-healing composite material. (4) The polyurethane composite material mixture obtained in step (3) is poured into a mold and baked at 60°C for 48 hours to completely remove DMF from the system. At this time, the mixture becomes a solid nanocomposite material.

[0047] Example 5: Application of Functionalized Graphene-Reinforced Polyurethane Nanocomposites The composite materials prepared in Examples 2-4 were applied to the surface of PA6 substrate in the form of a coating, and a composite coating system was prepared by spraying.

[0048] The results show that: (1) The coating system still exhibits excellent hydrogen barrier properties; the hydrogen permeability coefficient of the pure PA6 substrate is 3.552.23×10 -14 cm 3 ·cm / cm 2 The hydrogen permeability coefficients of the three coatings are 3.02 × 10⁻⁶ s·Pa. -14 cm 3 ·cm / cm 2 ·s·Pa, 2.85×10 -14 cm 3 ·cm / cm 2 ·s·Pa, 2.23×10 -14 cm 3 ·cm / cm 2 The gas barrier properties of ·s·Pa decrease with increasing content of functionalized graphene, indicating that the coating system prepared in this invention has superior gas barrier performance. (2) The feasibility of the material in practical engineering applications has been verified.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A functionalized graphene-reinforced polyurethane nanocomposite material, characterized in that: The composite material includes a polyurethane matrix containing Diels-Alder dynamic covalent bonds and functionalized graphene nanofillers dispersed in the polyurethane matrix; wherein, the surface of the functionalized graphene contains active groups that can chemically react with the polyurethane matrix, thereby forming Diels-Alder dynamic covalent bonds at the interface between the nanofiller and the matrix; the composite material simultaneously contains dynamic Diels-Alder bonds located in the polyurethane network and dynamic Diels-Alder bonds located at the filler-matrix interface, so as to construct a dynamic network structure in which the matrix and the interface work together.

2. The functionalized graphene-reinforced polyurethane nanocomposite material as described in claim 1, characterized in that: The functionalized graphene is a graphene oxide that has been surface-modified by a compound containing furan groups; the mass fraction of the functionalized graphene is 0.1-10% of the polyurethane matrix.

3. The method for preparing the functionalized graphene-reinforced polyurethane nanocomposite material as described in claim 1, characterized in that, The process includes the following steps: (1) uniformly dispersing graphene oxide in water or N,N-dimethylformamide, then adding furfurylamine to modify the graphene oxide, introducing furan rings on the surface of the graphene oxide to obtain functionalized graphene; (2) synthesizing polyurethane using polypropylene glycol, isophorone diisocyanate, furfurylamine, and 4,4'-bismaleimide diphenylmethane to obtain polyurethane containing dynamic Diels-Alder bonds; (3) dispersing the functionalized graphene in the polyurethane obtained in step (2); and (4) curing to obtain a nanocomposite material.

4. The preparation method according to claim 3, characterized in that: In step (1), the concentration of graphene oxide in water or N,N-dimethylformamide is 0.1-30 mg / mL, the mass ratio of graphene oxide to furfurylamine is 1:1-20, and furfurylamine and graphene oxide are ultrasonically dispersed or mechanically stirred in water or N,N-dimethylformamide, and then reacted at 100℃ for 1-20 h to complete the modification.

5. The preparation method according to claim 4, characterized in that: The concentration of graphene oxide in water or N,N-dimethylformamide was 2 mg / mL, the mass ratio of graphene oxide to furfurylamide was 1:5, and furfurylamide and graphene oxide were ultrasonically dispersed in water or N,N-dimethylformamide and then reacted at 100℃ for 12 h.

6. The preparation method according to claim 3, characterized in that: In step (2), polypropylene glycol and isophorone diisocyanate are mixed evenly, and dibutyltin dilaurate is added as a catalyst. The mixture is stirred and reacted for 1 h under a nitrogen atmosphere at 75 °C. Then, furfurylamine is dissolved in DMF and slowly added to the system. The mixture is stirred and reacted for another 1 h. Then, 4,4'-bismaleimide diphenylmethane is added and the mixture is stirred and reacted for another 4 h at 75 °C. The molar ratio of polypropylene glycol, isophorone diisocyanate, furfurylamine, and 4,4'-bismaleimide diphenylmethane is 1:2:2:

2.

7. The preparation method according to claim 3, characterized in that: In step (3), the functionalized graphene is mechanically stirred at 75°C and 50-500 rpm / min for 24 hours to achieve uniform dispersion in polyurethane; the mass fraction of the functionalized graphene is 0.1-5% of the polyurethane matrix.

8. The preparation method according to claim 3, characterized in that: In step (4), the curing process is to spray or coat the sample surface, or to place the mixture in a mold and pour it into shape, and then dry it at 60°C for 48 hours.

9. The application of the functionalized graphene-reinforced polyurethane nanocomposite material as described in any one of claims 1-8 as a coating material.

10. The application as described in claim 9, characterized in that: The coating material is applied to the surface of the substrate by spraying; the base layer is a polyamide material, a polyolefin material, or a polyester material.

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