High-toughness polyurethane composite material and preparation method thereof

Abstract

The invention relates to the field of high polymer materials, and discloses a high-toughness polyurethane composite material, which comprises the following components by mass: 60-72% of a polyurethane matrix; 3.0% to 5.0% of nano clay; 1.0%-2.0% of a graphene sheet layer; 0.5%-1.2% of a coupling agent; and the balance of auxiliary agents required in the preparation process. The thickness of the graphene sheet layer is 0.8 nm-1 nm, the coupling agent is an amino silane coupling agent, and the auxiliaries comprise a dispersing agent and a catalyst; the dispersing agent comprises a nonionic or anionic dispersing agent. A composite reinforcing system of nano clay and a graphene sheet layer is introduced into a polyurethane matrix, and the surface of a reinforcing phase is modified by using a coupling agent, so that good interface bonding and uniform dispersion between the reinforcing phase and the matrix are realized, and the elongation at break and the impact absorption capacity are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly to a high-toughness polyurethane composite material and a preparation method thereof. Background Art

[0002] Polyurethane (PU), as a typical thermosetting or thermoplastic polymer material, is widely used in many fields such as the automotive industry, building sealing, shoe materials, wearable electronics, cushioning protection, and medical auxiliary materials due to its excellent flexibility, mechanical strength, adjustable elastic modulus, and adaptability to various interfacial environments. Its structural characteristics stem from the microphase separation behavior of hard and soft segments, enabling the PU material to balance certain rigidity and elasticity at room temperature, providing a good basic framework for functional polymers.

[0003] However, with the rapid development of high-performance materials in the directions of extreme environments, structural-functional integration, and intelligent response, the performance boundaries of traditional polyurethane materials are gradually emerging. In particular, it is difficult to effectively balance strength, toughness, and fatigue resistance, which has become a key limitation for its expanded applications. Although standard polyurethane is compliant, under large strain or high-speed impact conditions, problems such as microcrack initiation, interfacial layer damage, and uncontrollable failure modes often occur, and the stability and repeated load-bearing capacity of the material are significantly insufficient.

[0004] To overcome the above problems, recent research has begun to explore introducing nano-fillers into the polyurethane system to improve material properties by constructing a composite phase structure. However, there are still many challenges in practical applications: a single reinforcing component is prone to uneven distribution in the polymer matrix, with strong inter-particle forces and obvious agglomeration effects, resulting in unstable interfacial energy of the composite system and interruption of the stress transfer path, which instead induces a new risk of crack propagation; while the high-filling strategy can improve rigidity, but often at the cost of sacrificing ductility and flexibility, causing enhanced brittleness and reduced failure threshold of the material. This "strong but not tough" characteristic is particularly prominent in dynamic load or repeated impact scenarios.

[0005] In addition, existing multi-phase polyurethane composite systems generally have common problems such as insufficient interfacial adhesion ability, single energy dissipation mechanism, and low utilization efficiency of the reinforcing phase, making it difficult to construct a stable, continuous, and synergistic nano-reinforcement network. Some technical routes attempt to adopt strategies such as covalent grafting, hydrogen bond assembly, or high cross-linking density design, but these methods are often complex in process, poor in controllability, and have a narrow processing window and high cost, which is not conducive to large-scale application and restricts the performance regulation and practical promotion of the materials. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a high-toughness polyurethane composite material and a preparation method thereof, which solve the problems that it is difficult to balance the toughness and strength of existing polyurethane materials, and the poor dispersion of nano-reinforcing phases and unstable interfacial bonding.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-toughness polyurethane composite material, comprising the following components in mass percentages: Polyurethane matrix 60% - 72%; Nanoclay 3.0% - 5.0%; Graphene sheets 1.0% - 2.0%; Coupling agent 0.5% - 1.2%; The balance is auxiliary agents required for the preparation process.

[0008] Preferably, the thickness of the graphene sheets is 0.8 nm - 1 nm, the coupling agent is an amino-silane coupling agent, and the auxiliary agents include a dispersant and a catalyst.

[0009] Preferably, the dispersant includes a non-ionic or anionic dispersant, selected from one or more of sodium dodecylbenzenesulfonate, polyether polyol modified dispersant, or polycarboxylic acid dispersant; The catalyst includes an organic tin catalyst or a tertiary amine catalyst for polyurethane reaction, specifically one or more of stannous octoate, dibutyltin dilaurate, or triethylenediamine.

[0010] Preferably, the composite material further includes a thermoelectric conversion material, and the thermoelectric conversion material is bismuth telluride, and the addition amount is 0.1% - 0.3% by mass percentage.

[0011] A preparation method of a high-toughness polyurethane composite material, comprising the following steps: S1. Surface modification of the nanoclay and graphene sheets; S2. Dispersing the modified nano-materials in a solvent to form a stable suspension; S3. Mixing the polyurethane matrix with the suspension under heating and stirring conditions to form a composite system; S4. Degassing the mixed system and injecting it into a mold for curing and molding, and the nanoclay and graphene sheets in the obtained composite material are distributed in a complementary and intercalated manner in the polyurethane matrix.

[0012] Preferably, in step S3, the polyurethane matrix is added dropwise to the nano-material suspension.

[0013] Preferably, in step S1, the mixing temperature is 80°C - 100°C, the stirring rate is 500 rpm - 700 rpm, and the mixing time is 30 minutes - 60 minutes.

[0014] Preferably, in the step S1, a coupling agent is used to modify the nano-clay and graphene sheets, so that an organic functional layer is formed on their surfaces, and this functional layer can chemically bond or form hydrogen bond interactions with the active groups in the polyurethane matrix.

[0015] Preferably, in the step S4, the defoaming process is carried out under a vacuum condition of -0.08 MPa to -0.1 MPa for 10 minutes to 20 minutes.

[0016] Preferably, in the composite system of the step S3, the nano-clay and graphene sheets are uniformly dispersed in the polyurethane matrix to form a composite network structure of the reinforcing phase, where the mass ratio of the nano-clay to the graphene sheets is 2:1 to 5:2, and the total amount of the reinforcing phase accounts for 4% to 6% of the mass of the composite material.

[0017] The present invention provides a high-toughness polyurethane composite material and a preparation method thereof. It has the following beneficial effects: 1. By introducing a composite reinforcement system of nano-clay and graphene sheets into the polyurethane matrix and using a coupling agent to modify the surface of the reinforcing phase, the present invention realizes good interfacial bonding and uniform dispersion between the reinforcing phase and the matrix, and obtains significantly improved elongation at break and impact absorption capacity.

[0018] 2. By optimizing the dispersion state of the nano-clay and graphene sheets in the polyurethane matrix and enhancing the synergistic effect between the two through chemical or physical bonding, the present invention improves the interfacial compatibility and stability between the reinforcing phase and the matrix and significantly improves the heat resistance performance.

[0019] 3. By optimizing the process flow and the selection of the composite formula, the present invention enables the nano-reinforcing phase to be quickly and uniformly dispersed in the polyurethane matrix, simplifies the material preparation process, realizes large-scale production and high-efficiency preparation, thereby reducing the manufacturing cost and improving the economic benefit.

[0020] 4. By introducing a thermoelectric conversion material into the composite material system to form a composite structure with energy conversion and storage functions, the present invention realizes the efficient conversion of mechanical energy or thermal energy into electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process preparation flow of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0023] Please refer to the attached Figure 1 , the present invention provides a high-toughness polyurethane composite material, which comprises components in the following mass percentages: Polyurethane matrix 60% - 72%; Nanoclay 3.0% - 5.0%; Graphene sheets 1.0% - 2.0%, with a thickness of 0.8 nm - 1 nm; Coupling agent 0.5% - 1.2%, which is an amino-silane coupling agent; The balance is auxiliaries required in the preparation process, and the auxiliaries include a dispersant and a catalyst.

[0024] A method for preparing a high-toughness polyurethane composite material comprises the following steps: S1. Surface-modify the nanoclay and graphene sheets; S2. Disperse the modified nano-materials in a solvent to form a stable suspension; S3. Mix the polyurethane matrix with the suspension under heating and stirring conditions to form a composite system; S4. Defoam the mixed system and inject it into a mold for curing and molding. In the obtained composite material, the nanoclay and graphene sheets are distributed in a complementary and intercalated manner in the polyurethane matrix.

[0025] Specifically, the high-toughness polyurethane composite material is composed of a polyurethane matrix, nanoclay, graphene sheets, an amino-silane coupling agent, and necessary dispersant and catalyst. The total content of nanoclay and graphene is controlled at 6.0% - 8.2% to avoid structural embrittlement while ensuring the strengthening effect. The thickness of graphene is controlled at 0.8 - 1 nm, which helps to construct an effective two-dimensional support path.

[0026] During the preparation process, first, a coupling agent is used to conduct surface modification treatment on the inorganic filler to endow it with higher dispersibility and interfacial affinity. After ultrasonic + stirring combined dispersion, the filler forms a stable suspension system in the solution. Subsequently, it is fully mixed with the polyurethane matrix under heating and stirring conditions, and then undergoes vacuum degassing and hot pressing curing to obtain a composite material with a uniform structure and continuous filler distribution. In the cured system, the filler does not exist in a completely embedded or isolated state, but presents a mesoscopic structure of "nested complementarity". Graphene is mainly distributed in the gaps between polyurethane chain segments, while nano-clay forms partial oriented stacking, interpenetrating spatially with the graphene boundary region to construct an effective mechanical conduction and buffering network.

[0027] The material exhibits outstanding comprehensive performance in the tensile test. The tensile strength is stable in the range of 62 - 70 MPa, the elongation at break can reach 320 - 400%, and the elastic modulus remains above 30 MPa. Compared with the pure polyurethane control material, the fracture strength is increased by more than 70%, while the ductility is not significantly weakened.

[0028] Scanning electron microscopy analysis reveals that the crack propagation path deflects frequently, forming an obvious energy dissipation structure in the crack tip region, indicating that the reinforcing phase not only improves the strength but also changes the fracture mechanism of the material. The addition of the coupling agent enhances the adhesion performance between the inorganic phase and polyurethane, reducing the probability of interfacial debonding. Especially under conditions of multiple loading or high strain rates, the interface stability of the material is better than that of the uncoupled samples. This multi-phase synergistic reinforcement structure effectively absorbs the energy generated by external loads while maintaining the overall continuity and elasticity of the material, which is the key to the realization of its "high strength + high toughness" performance.

[0029] Compared with the existing polyurethane materials based on single filler reinforcement or high cross-linking density regulation, the structural design of this material is more flexible and adaptable. Without increasing the brittleness of the matrix, by synergistically constructing a microscopic network of graphene and nano-clay, multiple goals of crack control, load transfer, and interfacial toughening are achieved. The use strategy of the coupling agent further solves the problem of unstable interfaces in traditional composite systems, making the reinforcement effect evolve from simple physical filling to a participant in structural interaction. This material has good molding processability and performance stability, and is suitable for multi-scenario requirements such as flexible protection, structural buffer layers, and wear-resistant elastic components, showing obvious technical advantages and application expansion space in the field of high-performance polyurethane materials.

[0030] Based on the same inventive concept and preparation steps, the following examples are given: Example 1: Preparation of high-strength and high-toughness polyurethane composite material: Material ratio: Polyurethane matrix: 65%; Nano-clay: 3.8%; Graphene sheets: 1.3%; Coupling agent: 0.8%; Auxiliary agent: the balance.

[0031] Preparation steps: S1. Disperse the nanoclay in deionized water and stir evenly to obtain a homogeneous suspension.

[0032] S2. Add graphene sheets and treat with ultrasonic waves for 10 minutes to improve the dispersion effect.

[0033] S3. Add the coupling agent and continue stirring for 20 minutes to enhance the interfacial bonding force between components.

[0034] S4. Mix the mixture evenly with the polyurethane matrix, pour it into a mold, and cure at 80 °C for 6 hours.

[0035] S5. After curing, conduct natural cooling, take out the sample and conduct mechanical property tests.

[0036] Test example 1: Ultrasonic-assisted dispersion method: Experimental steps: Accurately weigh 3.8 g of nanoclay, add it to 50 mL of deionized water, and magnetically stir at room temperature for 15 min.

[0037] Treat the system with an ultrasonic dispersion device for 10 min, set the frequency to 20 kHz and the power to 150 W to enhance the interlayer peeling effect of the nanoclay.

[0038] Add 1.3 g of graphene sheets to the above dispersion liquid and continue ultrasonic treatment for 5 min to ensure its uniform distribution.

[0039] Add 0.8 g of γ-aminopropyltriethoxysilane (KH-550) coupling agent and stir for 30 min to promote the adhesion between the inorganic component and the polyurethane interface.

[0040] Mix the obtained slurry with 65 g of polyurethane prepolymer and mechanically stir at 500 rpm for 20 min.

[0041] Inject the mixture into a mold, cure at a constant temperature of 80 °C for 6 h, cool at room temperature for 24 h after demolding, and prepare samples for testing.

[0042] Test results of the mechanical properties of Example 1: Test Index Value Tensile Strength (MPa) 65.0 Elongation at Break (%) 300 Elastic Modulus (MPa) 38.2 <![CDATA[Density (g / cm 3 )]]> 1.14 Scanning electron microscope images show that graphene sheets are distributed in irregular layers in the polyurethane matrix, some sheets are embedded and coupled with nanoclay, and synergistic interlaced interfaces are formed in local areas. Although an idealized three-dimensional network is not constructed, these microscopic "nodes" have obvious transfer and release effects during stress loading, which effectively disperses the load before local concentration, reducing the risk of early failure of the material.

[0043] Different from the traditional single nanofiller reinforcement method, the present invention constructs a multi-scale mechanical support structure in the polyurethane matrix through the dual-component composite of graphene and nanoclay. The crack propagation path is deflected due to the interface energy gradient, and the local interface microstructure plays a role in crack delay and shielding. The material shows obvious tensile hysteresis behavior before fracture, which is an uncommon feature in existing homogeneous reinforcement systems.

[0044] Nanoclay mainly plays a supporting and rigid reinforcement role, while graphene sheets guide the reconstruction of stress conduction paths. The two are not simply superimposed, but synergistically linked to significantly improve the fracture strength and toughness. The measured tensile strength reaches 65MPa, far exceeding the typical level of pure polyurethane materials (generally 30-40MPa), and the elongation at break is also maintained at more than 300%, with good ductility.

[0045] Although the introduction of the coupling agent is not obvious in appearance, the number of debonding interfaces is significantly reduced in the observation of the interface layer, and the adhesion integrity is higher. Compared with the control sample without the coupling agent, the interface energy is significantly improved, which effectively inhibits the filler peeling and the early initiation of interface cracks. This interface bridging mechanism is the key link in promoting the synergistic enhancement of strength and toughness of the system.

[0046] Overall, compared with the contradiction between the increase in rigidity and the loss of toughness caused by the single reinforcement method in the prior art, the present invention achieves a balanced breakthrough in mechanical properties through structural hierarchical composite design, synergistic effect of dual nanofillers and interface optimization. The material strength, ductility and interface stability are all improved simultaneously, reflecting the excellent comprehensive performance potential.

[0047] Example 2: Preparation and optimization of high-toughness polyurethane composite materials: Material ratio: polyurethane matrix: 70%; nanoclay: 3.5%; graphene sheet: 1.5%; coupling agent: 0.6%; auxiliary agent: balance.

[0048] Preparation steps: S1. Add nanoclay into deionized water and stir to keep it dispersed stably.

[0049] S2. Add graphene sheets and perform high-speed shear stirring for 15 minutes.

[0050] S3. Add a coupling agent and continue stirring for 10 minutes, then mix with the polyurethane matrix.

[0051] S4. Pour the mixture into a mold and cure at 90 °C for 4 hours.

[0052] S5. After curing, cool the sample and conduct mechanical tests.

[0053] Test Example 2: Slow Shear Composite Method: Experimental Procedure: Weigh 3.5 g of nano-clay and slowly add it to 70 g of polyurethane prepolymer. Stir at 600 rpm for 15 min to ensure uniform dispersion.

[0054] Pre-mix 1.5 g of graphene sheets with 0.6 g of coupling agent, ultrasonically treat for 3 min, then add it to the main system and continue stirring for 30 min.

[0055] After the mixture is degassed under vacuum (0.08 MPa, 10 min), inject it into a mold.

[0056] Cure at 90 °C for 4 h, prepare standard specimens after demolding and cooling, and conduct performance tests.

[0057] Table of Mechanical Property Test Results of Example 2: Test Index Value Tensile Strength (MPa) 62.6 Elongation at Break (%) 344 Elastic Modulus (MPa) 34.1 <![CDATA[Density (g / cm 3 )]]> 1.11 The elongation at break of the sample was significantly increased to 344%, while the tensile strength remained above 62 MPa, indicating that the material not only has high ductility but also sufficient structural bearing capacity. Observation of the details of the fracture surface of the material shows that the reinforcing phase forms a continuous interfacial zone with an obvious "pulling feeling" in the polyurethane matrix, which is a direct reflection of the effective compatibility between the filler and the matrix.

[0058] Under slow shear conditions, nano-clay forms local oriented stacking. The layered structure does not fully spread, but provides microscopic support units that can resist local stress concentration in the initial stage of loading. Graphene sheets are dispersed in the surrounding area to form a flexible reinforcement structure. The two are not homogeneously distributed, but have a functional division in space, which is conducive to the formation of hierarchical load transfer.

[0059] Traditional reinforcement systems generally have problems such as aggregation of rigid reinforcements, poor interfacial adhesion, and insufficient toughening ability. The present invention utilizes the process window of slow shear to control the distribution mode of nano-sheets, improving the elastic modulus while avoiding brittle reinforcement phenomena caused by excessive cross-linking or filler aggregation. The presence of the coupling agent is also crucial, making the inorganic / organic phase interface more compliant and enhancing the interfacial durability during the stress process.

[0060] Based on the structural fine-tuning, the balance of stress-strain behavior is achieved. This "asymmetric enhancement" method is different from the traditional filler saturated filling path, and the material shows more tolerant deformation ability and more stable mechanical response. Its application space extends from structural materials to flexible fields such as buffers, wearables, and composite coatings, with strong application migration ability.

[0061] Example 3: Preparation of surface-modified reinforced composite material: Material ratio: polyurethane matrix: 66%; surface-modified nano-clay: 4.0%; ultra-thin graphene sheets: 1.5%; coupling agent: 0.7%; additives: the balance.

[0062] Preparation steps: S1. Surface-modify the nano-clay with a surfactant to prepare modified nano-clay.

[0063] S2. Mix the modified nano-clay with graphene sheets, add a coupling agent, and stir evenly.

[0064] S3. Mix the mixture with the polyurethane matrix, and stir and mix evenly at 100 °C.

[0065] S4. Pour it into a mold and cure at 100 °C for 5 hours to obtain the composite material.

[0066] S5. After the sample is naturally cooled, perform mechanical property tests.

[0067] Test Example 3: Surface-modified filler blending method: Experimental steps: Use a surfactant (sodium dodecyl sulfate) to surface-treat the nano-clay to obtain 4.0 g of modified nano-clay.

[0068] Mix it with 1.5 g of ultra-thin graphene sheets and 0.7 g of KH-550 coupling agent, and ultrasonically disperse in deionized water for 10 min.

[0069] After adding 66 g of polyurethane matrix, stir at high shear (1000 rpm) for 25 min.

[0070] Mold and cure at 100 °C for 5 h. After preparation, perform conventional cooling and performance tests.

[0071] Table of mechanical property test results of Example 3: Test Index Value Tensile Strength (MPa) 70.0 Elongation at Break (%) 400 Elastic Modulus (MPa) 40.3 <![CDATA[Density (g / cm 3 )]]> 1.17 Nanoclay treated by surface modification shows higher dispersion stability, less agglomeration in microscopic structural observation, and a certain interlayer spacing between the sheets. This loose but stable structural state helps to form a wider distribution area in the polyurethane matrix, and the filler has a stronger presence in the entire composite system.

[0072] The role of graphene is more obvious in this system. There is an incomplete separation between graphene and nanoclay, which constructs a multi-point interlocking interface, making the stress loading path more tortuous. This complex stress migration path effectively increases the energy consumption demand for crack propagation and is one of the foundations for the composite material to show a tensile strength of 70MPa. It is worth noting that the elongation at break remains at 400%, indicating that toughness has not been sacrificed.

[0073] Compared with the existing system based on chemical cross-linking to improve strength, the present invention focuses more on building a multi-scale synergistic network through physical configuration regulation, thereby achieving simultaneous improvement of strength and ductility. The reasonable addition of coupling agent plays a role in "lubricating" the interface, making the contact between the organic chain segment and the inorganic sheet smoother, and reducing the debonding inducement from a microscopic perspective.

[0074] More importantly, this composite structure has good stability, and no obvious microcrack initiation is observed under repeated loading conditions. The structural layers are not rigidly connected, but a medium-strong interface between physical entanglement and weak chemical bonds, which gives the system a certain recovery ability. This gives it a potential advantage in load-buffer alternating cycle applications.

[0075] Example 4: Preparation of self-powered intelligent composite material: Material ratio: polyurethane matrix: 67%; nanoclay: 3.5%; graphene sheet: 1.6%; coupling agent: 0.7%; bismuth telluride powder: 0.3%; auxiliary agent: balance.

[0076] Preparation steps: S1. Add bismuth telluride powder into the polyurethane matrix, stir and disperse thoroughly.

[0077] S2. Add the mixture of nanoclay and graphene sheets and continue stirring.

[0078] S3. Add coupling agent and keep stirring evenly.

[0079] S4. Pour the mixture into a mold and cure at 85°C for 8 hours.

[0080] S5. After the sample is cooled, the thermoelectric and mechanical properties are tested.

[0081] Test Example 4: Functional filler collaborative dispersion method: Experimental steps: Add 0.3 g of bismuth telluride powder to 70 g of polyurethane and disperse it by three-roll grinding three times to ensure its uniform embedding in the matrix.

[0082] Weigh 3.5 g of nano-clay and 1.6 g of graphene sheets respectively, mix them with 0.7 g of coupling agent, and stir ultrasonically for 10 min.

[0083] Compound the above two parts, stir at low speed for 15 min, and inject into the mold after defoaming treatment.

[0084] Cure at 85 °C for 8 h, prepare samples after cooling, and test the mechanical and thermoelectric properties.

[0085] Table of performance test results for Example 4: Test Index Value Tensile Strength (MPa) 68.0 Elongation at Break (%) 370 Thermoelectric Power Factor (mW / m·K2) 0.22 <![CDATA[Density (g / cm 3 )]]> 1.19 In this system, the thermoelectric functional particles (bismuth telluride) and graphene, nano-clay jointly construct a composite path. Different from the previous examples that mainly focused on mechanical properties, this experiment took into account both structural mechanics and electrical performance. The thermoelectric power factor reached 0.22 mW / m·K2, which is already close to the performance range of some conductive elastomers. Not all particles are evenly distributed, but some chain-like conductive structures form available electron migration paths.

[0086] A short-range coupling effect is formed between graphene and bismuth telluride, which is beneficial to electron conduction; nano-clay mainly acts on stabilizing the structure and restricting the deformation of the conductive channels under thermal disturbance. This synergistic structure realizes the local coincidence of the stress field and the electric field at the microscale, which is the key to enhancing its multi-functional response ability.

[0087] Compared with the traditional conductive filler system, the conventional system often has the problem of a sharp decline in mechanical properties while improving the electrical conductivity. However, the present invention successfully balances the contradiction between the conductivity and the fracture properties through a multi-component synergistic strategy. The strength of 68 MPa and the elongation at break of 370% indicate that the material can still maintain integrity and usability under external excitation conditions.

[0088] From the process level, the three-roll grinding technology improves the embedding degree of the conductive filler and polyurethane, rather than relying on excessive accumulation of the filler. The presence of the coupling agent further stabilizes the interfacial adhesion force between multiple components. This "weak coupling - strong response" structural design provides platform-level material support for constructing wearable, self-powered or responsive flexible devices.

[0089] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-toughness polyurethane composite material, characterized in that: The following components are included in mass percentage: Polyurethane matrix 60%~72%; Nanoclay 3.0% to 5.0%; Graphene sheet 1.0%~2.0%; Coupling agent 0.5%~1.2%; The rest are auxiliary agents required for the preparation process.

2. A high-toughness polyurethane composite material according to claim 1, characterized in that: The thickness of the graphene sheet is 0.8nm-1nm, the coupling agent is an aminosilane coupling agent, and the auxiliary agent includes a dispersant and a catalyst.

3. A high-toughness polyurethane composite material according to claim 2, characterized in that: The dispersant includes a nonionic or anionic dispersant, selected from one or more of sodium dodecylbenzene sulfonate, a polyether polyol modified dispersant or a polycarboxylic acid dispersant; The catalyst includes an organic tin catalyst or a tertiary amine catalyst for polyurethane reaction, specifically one or more of stannous octoate, dibutyltin dilaurate or triethylenediamine.

4. The high-toughness polyurethane composite material according to claim 1, characterized in that: The composite material also includes a thermoelectric conversion material, and the thermoelectric conversion material is bismuth telluride, and the added amount is 0.1% to 0.3% by mass.

5. A method for preparing a high-toughness polyurethane composite material, according to the high-toughness polyurethane composite material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Surface modification of nanoclay and graphene sheets; S2. dispersing the modified nanomaterial in a solvent to form a stable suspension; S3. The polyurethane matrix and the suspension are mixed under heating and stirring conditions to form a composite system; S4. Degas the mixed system and inject it into a mold for solidification and molding. In the obtained composite material, nanoclay and graphene sheets are distributed in the polyurethane matrix in a complementary mosaic manner.

6. The method for preparing a high-toughness polyurethane composite material according to claim 5, characterized in that: In the step S3, the polyurethane matrix is ​​added dropwise into the nanomaterial suspension.

7. The method for preparing a high-toughness polyurethane composite material according to claim 5, characterized in that: In the step S1, the mixing temperature is 80° C. to 100° C., the stirring rate is 500 rpm to 700 rpm, and the mixing time is 30 minutes to 60 minutes.

8. The method for preparing a high-toughness polyurethane composite material according to claim 5, characterized in that: In the step S1, a coupling agent is used to modify the nanoclay and graphene sheet so that an organic functional layer is formed on the surface of the two. The functional layer can chemically combine with the active groups in the polyurethane matrix or form hydrogen bonds.

9. The method for preparing a high-toughness polyurethane composite material according to claim 5, characterized in that: The degassing process in the step S4 is carried out under a vacuum condition of -0.08 MPa to -0.1 MPa for 10 to 20 minutes.

10. The method for preparing a high-toughness polyurethane composite material according to claim 5, characterized in that: In the composite system in step S3, nanoclay and graphene sheets are uniformly dispersed in the polyurethane matrix to form a composite network structure of a reinforcement phase, wherein the mass ratio of nanoclay to graphene sheets is 2:1 to 5:2, and the total amount of the reinforcement phase accounts for 4% to 6% of the mass of the composite material.

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