VO2-coated 3GO-based composite modified granulated TPU and preparation method thereof

Abstract

The invention relates to the technical field of thermoplastic polyurethane elastomers, and particularly discloses VO2-at-3GO-based composite modified granulated TPU (thermoplastic polyurethane) and a preparation method thereof in order to solve the problems of poor comprehensive properties such as easy yellowing and low flame retardance of the existing TPU phase change material. The VO2-coated 3GO composite modified granulated TPU is prepared from the following components in parts by weight: 70 to 90 parts of TPU base material, 5 to 25 parts of VO2-coated 3GO composite system, 0.1 to 1 part of antioxidant, 0.1 to 0.5 part of light stabilizer and 0.1 to 0.5 part of lubricant, the VO2-coated 3GO composite system comprises modified VO2 nano powder and GQDs grafted modified 3GO, and the surface of the modified VO2 nano powder forms a bifunctional modified composite interface layer through a silane coupling agent and maleic anhydride. According to the invention, a modified and compounded VO2-coated 3GO composite system is introduced into a TPU base material, and through the synergistic effect of all the components, the performance problems of easy yellowing, low flame retardance and the like of the existing TPU phase change material can be solved.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic polyurethane elastomer technology, and more specifically, to a VO2@3GO composite modified granulated TPU and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU) is a block linear copolymer polymerized from diisocyanate, macromolecular polyol, and chain extender through reaction polymerization, possessing excellent physical and mechanical properties and processing performance. However, traditional TPU has limitations in functional performance, such as insufficient thermal conductivity, and also suffers from problems during production and processing, such as easy yellowing, low flame retardancy, and difficulty in hardness adjustment, thus making it difficult to meet the application requirements of high-end technology fields.

[0003] Based on the above, some technical means to improve the material properties of TPU by compounding functional raw materials are proposed. For example, patent CN112126208A proposes a phase change temperature control material and its preparation method, the raw materials of which include the following components in parts by weight: 70-100 parts of main resin; 1-10 parts of phase change metal oxide powder; 5-20 parts of organic phase change material; 8-25 parts of thermally conductive powder; 1-5 parts of amphiphilic dispersant; 0-5 parts of compatibilizer; and 0.1-1 parts of antioxidant.

[0004] However, existing phase change temperature control materials, such as those mentioned above, suffer from defects such as uneven dispersion of phase change metal oxides and poor functional synergy due to the complexity and large number of raw material components. Therefore, there is an urgent need for a phase change thermoplastic polyurethane elastomer material with high material dispersion and better comprehensive performance, as well as its preparation process. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of insufficient overall performance of existing TPU phase change materials, such as easy yellowing and low flame retardancy.

[0006] This invention is achieved through the following technical solution: This invention provides a VO2@3GO composite modified granulated TPU, comprising, by weight, 70-90 parts TPU base material, 5-25 parts VO2@3GO composite system, 0.1-1 parts antioxidant, 0.1-0.5 parts light stabilizer, and 0.1-0.5 parts lubricant; the VO2@3GO composite system comprises modified VO2 nanopowder and GQDs grafted modified 3GO, wherein the surface of the modified VO2 nanopowder is modified with a silane coupling agent and maleic anhydride to form a bifunctional composite interface layer.

[0007] Preferably, the modified VO2 nanopowder is obtained by pretreatment of VO2 nanopowder, and the pretreatment process is as follows: A1 Take VO2 nanoparticles with a particle size of 50-200nm and dry them under vacuum at 60-100℃; A2 Then, VO2 nanopowder is added to hydrogen peroxide solution, submerged, and stirred and soaked at 65-75℃. It is then washed with deionized water and dried under vacuum at 80-90℃. A3 Take 5 parts by weight of VO2 nanopowder and add it to anhydrous ethanol. Disperse it by ultrasonication, then add 0.2-1.5 parts by weight of silane coupling agent and 0.3-0.6 parts by weight of maleic anhydride. Reflux the mixture at 70-80℃, centrifuge and dry to obtain the modified VO2 nanopowder.

[0008] Preferably, in step A2, before immersion, the solid-liquid ratio is controlled to be 8-12:1; the mixture is stirred and soaked for 2-3 hours, and then washed with deionized water until neutral.

[0009] Preferably, in step A3, before ultrasonic dispersion, the solid-liquid ratio is controlled to be 6-10:1; ultrasonic dispersion is performed for 30-45 minutes, followed by reflux reaction for 4-5 hours.

[0010] Preferably, the GQDs-grafted modified 3GO is obtained by pretreatment of triethylene glycol diisooctanoate, and the pretreatment process is as follows: B1. Add 15-18 parts by weight of triethylene glycol diisooctanoate to a solvent, stir to dissolve, then add 0.2-1.2 parts by weight of amino-based graphene quantum dots with a particle size of 2-5 nm, place at 85-95℃ and stir to react, then distill under reduced pressure until the solvent is completely removed to obtain the GQDs-grafted modified 3GO.

[0011] Preferably, in step B1, the solid-liquid ratio of triethylene glycol diisooctanoate to solvent is 3-8:1; the reaction is stirred for 6-8 hours.

[0012] Preferably, the preparation method of the VO2@3GO composite system is as follows: C1 Take 3-8 parts by weight of modified VO2 nanopowder, 15-20 parts by weight of GQDs grafted modified 3GO, 0.8-2 parts by weight of phosphorus and nitrogen flame retardant synergist and 0.2-0.6 parts by weight of composite anti-mutation agent, mix them, disperse them at 2000-5000 rpm for 15-180 min, and then grind them to obtain VO2@3GO mixture; C2. The VO2@3GO mixture is aged at 40-60℃ for 12-48 hours to obtain the VO2@3GO composite system.

[0013] Preferably, the phosphorus-nitrogen flame retardant synergist comprises ammonium polyphosphate and melamine cyanurate in a mass ratio of 2:08-1.2; the composite anti-mutation agent comprises hindered phenolic antioxidant and ultraviolet absorber in a mass ratio of 3:1.8-2.2.

[0014] The present invention also provides a method for preparing the above-mentioned VO2@3GO composite modified granulated TPU, comprising the following steps: S1 mixes TPU base material with VO2@3GO composite system, antioxidant, light stabilizer and lubricant, and stirs at 800-2000 rpm to obtain premix; S2 feeds the premixed material into a twin-screw extruder for melt blending. Segmented temperature control is used, with the screw temperature controlled sequentially at 160-165℃, 170-180℃, 185-190℃, and 190-200℃. After S3 extrusion, underwater air-cooled pelletizing is used for pelletizing. The pellets are then graded and screened, and then heated and dried to obtain the VO2@3GO composite modified granulated TPU.

[0015] Preferably, in step S3, the material is first cooled by water at a depth of 50-100 cm, then granulated by air cooling at a depth of 10-20 m; then it is first passed through a 10-mesh sieve to remove large particles, and then through an 80-mesh sieve to remove fine powder; finally, it is placed in an environment of -0.09 to -0.08 MPa and 70-90℃ and dried for 2-8 hours to obtain the VO2@3GO composite modified granulated TPU.

[0016] The technical solution of the present invention has the following beneficial effects: (1) The phase change temperature control characteristics of VO2 are combined with the high thermal conductivity of GQDs to form a dual functional mechanism of phase change heat absorption and rapid heat conduction. The modified TPU material of this invention has a thermal conductivity of up to 1.85 W / (m·K), and achieves precise phase change temperature control in the 65-75℃ range, improving thermal response efficiency by more than 30%, which can meet the stringent requirements of high-end electronic devices, automotive interiors, etc. for temperature control and heat conduction.

[0017] (2) By compounding the phosphorus and nitrogen flame retardant synergist of APP-MCA with the hindered phenol-ultraviolet absorber to form a composite anti-variant, and forming a comprehensive functional synergy with the modified composite system, the flame retardant and anti-yellowing performance are simultaneously improved. The limiting oxygen index (LOI) of this modified TPU material is up to 35.2%, and the flame retardant level can reach UL94V-0. After 1000h of ultraviolet aging, the yellowing index ΔE≤1.1 can effectively extend the service life of the product and adapt to complex application environments such as outdoor and high temperature.

[0018] (3) While achieving multiple functional improvements, this invention optimizes process parameters such as segmented temperature control, graded sieving, and vacuum drying, as well as enhances the interfacial bonding force of the composite system, ensuring stable mechanical properties of the product. Its tensile strength can reach up to 38.6 MPa, its elongation at break can be maintained above 520%, and its hardness (Shore A) can be flexibly adjusted between 75 and 88. This not only solves the problem of functional improvement accompanied by decreased mechanical properties in existing modification schemes, but also adapts to the different requirements of material hardness in different scenarios. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents, or raw materials used are not specified, they are all conventional products that can be purchased commercially.

[0020] This invention provides a VO2@3GO composite modified granulated TPU, comprising, by weight, 70-90 parts TPU base material, 5-25 parts VO2@3GO composite system, 0.1-1 parts antioxidant, 0.1-0.5 parts light stabilizer, and 0.1-0.5 parts lubricant; The VO2@3GO composite system can be selected in 5-10 parts or 10-25 parts. The low dosage focuses on hardness adjustment, while the high dosage focuses on thermal conductivity / flame retardancy, so as to adapt to different application scenarios and needs.

[0021] In this invention, the preparation process of the VO2@3GO composite system is as follows: (1) Pretreatment of VO2 nanopowder: 1.1 Pretreatment: Take VO2 nanoparticles with a particle size of 50-200nm and place them in a vacuum dryer at 60-100℃ for 4-6h to remove surface adsorbed water.

[0022] 1.2 Hydroxylation Modification: Take 5 parts (dry weight) of pretreated VO2 nanopowder and add it to a 5-8 wt% hydrogen peroxide solution at a solid-liquid ratio of 8-12:1, ensuring complete immersion. Stir at 65-75℃ for 2-3 hours, then wash with deionized water until neutral, and finally vacuum dry at 80-90℃ for 2-3 hours. Through the oxidation of hydrogen peroxide, a large number of hydroxyl groups are introduced onto the VO2 surface, breaking the surface inertness of VO2 and providing reaction sites for subsequent coupling agent grafting.

[0023] 1.3 Construction of the composite interface layer: Take 5 parts (dry weight) of hydroxylated VO2 nanoparticles and add them to anhydrous ethanol at a solid-liquid ratio of 6-10:1. Disperse ultrasonically for 30-45 min, then add 0.2-1.5 parts of silane coupling agent and 0.3-0.6 parts of maleic anhydride. Reflux at 70-80℃ for 4-5 h, then centrifuge and dry to form a bifunctionalized composite interface layer on the surface of the VO2 nanoparticles. The alkoxy group of the silane coupling agent undergoes a condensation reaction with the hydroxyl group on the VO2 surface, and the double bond functional group can undergo an addition reaction with the amino group of the TPU molecular chain. The carboxyl group of maleic anhydride can form hydrogen bonds with the ester group of 3GO, forming a chemical bond connection of VO2-coupling agent-maleic anhydride-3GO / TPU. This completely solves the problem of weak interfacial bonding between the existing composite raw material system and the TPU matrix, while inhibiting the aggregation of nanoparticles.

[0024] (2) Pretreatment of triethylene glycol diisooctanoate (3GO): 2.1 Take 15-18 parts of 3GO with a dry weight of ≥99.5% purity, add it to N,N-dimethylformamide (DMF) at a solid-liquid ratio of 3-8:1, stir to dissolve, then add 0.2-1.2 parts of aminographene quantum dots (GQDs-NH2) with a particle size of 2-5nm, place it at 85-95℃ and stir to react for 6-8h, remove DMF by vacuum distillation to obtain GQDs-grafted modified 3GO, denoted as GQDs@3GO. By undergoing an amidation reaction between the amino group of GQDs-NH2 and the ester group of 3GO, GQDs are grafted onto the 3GO molecular chain. The excellent thermal conductivity of GQDs can compensate for the poor thermal conductivity of the original 3GO. At the same time, its quantum confinement effect can work synergistically with the phase change characteristics of VO2. When the ambient temperature rises, VO2 undergoes a phase change and absorbs heat, while GQDs rapidly conduct heat, achieving the dual functions of temperature control and heat conduction. This solves the problem that traditional phase change materials rely solely on VO2 for temperature control and have low thermal response efficiency.

[0025] (3) Raw material compounding 3.1 Take 3-8 parts (dry weight) of the pretreated VO2 nanopowder and 15-20 parts (dry weight) of GQDs-grafted modified 3GO, mix with 0.8-2 parts (dry weight) of phosphorus-nitrogen flame retardant synergist and 0.2-0.6 parts (dry weight) of composite anti-regulatory agent, place in a nano-milling mill, and pre-disperse at 2000-5000 rpm for 15-180 min; then transfer to a three-roll mill, adjust the roller spacing to 5-20 μm, and mill 5-10 times to obtain a uniform VO2@3GO mixture; wherein, the phosphorus-nitrogen flame retardant synergist includes ammonium polyphosphate (APP) and melamine cyanurate (MCA) in a mass ratio of 2:08-1.2, and the composite anti-regulatory agent includes hindered phenolic antioxidant and ultraviolet absorber in a mass ratio of 3:1.8-2.2.

[0026] 3.2 Curing treatment: Place the VO2@3GO mixture at 40-60℃ for 12-48h to allow 3GO to fully wet the surface of VO2, thus obtaining VO2@3GO composite slurry.

[0027] The VO2@3GO composite modified granulated TPU of this invention is prepared by the following steps: (1) Take the required amount of each raw material component and set aside.

[0028] (2) Add the TPU base material, VO2@3GO composite system, antioxidant, light stabilizer and lubricant to a high-speed mixer and stir at 800-2000 rpm for 5-15 minutes to form a uniform premix.

[0029] (3) The premixed material is fed into a twin-screw extruder for melt blending. The temperature is controlled in stages, with the screw temperature controlled sequentially at 160-165℃ (feeding section), 170-180℃ (melting section), 185-190℃ (mixing section), and 190-200℃ (extrusion section) to avoid local high temperature causing TPU degradation and yellowing. During this period, the screw speed is controlled at 200-400 rpm.

[0030] (4) The extruded melt is extruded through a die and granulated by underwater air cooling pelletizing. First, it is cooled by water at 50-100cm and then granulated by low-temperature air cooling at 10-20m. Then, the granules are graded and screened. First, they are sieved through a 10-mesh sieve to remove large particles and then through an 80-mesh sieve to remove fine powder, so as to ensure that the particle size is uniform, the particle size range is 1-3mm, and the particle size deviation is ≤0.2mm. Finally, it is placed in an environment of -0.09 to -0.08MPa and 70-90℃ for 2-8h to avoid high-temperature oxidation and further reduce the risk of yellowing, so as to obtain composite modified granulated TPU products.

[0031] Example 1 (1) This embodiment uses a high-volume VO2@3GO composite system, focusing on thermal conductivity and flame retardant properties. The raw material formulation is as follows (by mass): ①TPU base material (model 1185A): 75 parts; ②VO2@3GO complex system: 22 samples; The raw materials include 5 parts modified VO2 nanopowder (particle size 100nm), 15 parts 0.5GQDs@3GO, 1.5 parts phosphorus and nitrogen flame retardant synergist (APP:MCA=2:1), and 0.5 parts composite anti-yellowing agent (hindered phenol 1010:UV531=3:2). After mixing the raw materials, they were pre-dispersed at 3000rpm for 60min, ground 8 times with a roller gap of 10μm using a three-roll mill, and cured at 50℃ for 24h to obtain the VO2@3GO composite system. ③ Antioxidant (1076): 0.3 parts; ④ Light stabilizer (UV-3808PP5): 0.3 parts; ⑤ Lubricant (zinc stearate): 0.2 parts.

[0032] (2) The above five raw material components are placed in a high-speed mixer and stirred at 1500 rpm for 10 min. Then, the material is extruded through a twin-screw extruder with the screw speed controlled at 300 rpm and the screw section temperatures at 160℃, 175℃, 185℃ and 195℃ respectively. The material is then cooled by 80 cm water and 15 m air cooling to form pellets. The pellets are then sieved through an 80-mesh screen to remove fine powder. Finally, the pellets are placed in an environment of -0.08 MPa and 80℃ and dried for 4 h to obtain modified TPU pellets.

[0033] Example 2 (1) This embodiment uses a medium-dosage VO2@3GO composite system, focusing on the balance of multiple properties. The raw material formula is (by mass): ①TPU base material (model 1185A): 82 parts; ②VO2@3GO complex system: 15 parts; The raw materials include 3 parts modified VO2 nanopowder (particle size 150nm), 11 parts 0.3GQDs@3GO, 0.8 parts phosphorus and nitrogen flame retardant synergist (APP:MCA=2:1), and 0.2 parts composite anti-yellowing agent (hindered phenol 1010:UV531=3:2). After mixing the raw materials, they were pre-dispersed at 2500rpm for 40min, milled 6 times with a three-roll mill roller spacing of 15μm, and aged at 45℃ for 18h to obtain the VO2@3GO composite system. ③ Antioxidant (1076): 0.2 parts; ④ Light stabilizer (UV-3808PP5): 0.2 parts; ⑤ Lubricant (zinc stearate): 0.1 parts.

[0034] (2) The above five raw material components are placed in a high-speed mixer and stirred at 1200 rpm for 8 min. Then, the material is extruded through a twin-screw extruder with the screw speed controlled at 280 rpm and the screw segment temperatures at 162℃, 172℃, 186℃ and 192℃ respectively. The material is then granulated by cooling with 70 cm water and 12 m air, and then sieved through an 80-mesh screen to remove fine powder. Finally, the material is placed in an environment of -0.08 MPa and 75℃ and dried for 3 h to obtain modified TPU granules.

[0035] Example 3 (1) This embodiment uses a low-dosage VO2@3GO composite system, focusing on hardness adjustment. The raw material formula is (by mass): ①TPU base material (model 1185A): 88 parts; ②VO2@3GO complex system: 9 parts; The raw materials include 2 parts modified VO2 nanopowder (particle size 200nm), 6.5 parts 0.2GQDs@3GO, 0.3 parts phosphorus and nitrogen flame retardant synergist (APP:MCA=2:1), and 0.1 parts composite anti-yellowing agent (hindered phenol 1010:UV531=3:2). After mixing the raw materials, they were pre-dispersed at 2000rpm for 30min, ground 5 times with a roller gap of 20μm using a three-roll mill, and cured at 40℃ for 12h to obtain the VO2@3GO composite system. ③ Antioxidant (1076): 0.1 parts; ④ Light stabilizer (UV-3808PP5): 0.1 parts; ⑤ Lubricant (zinc stearate): 0.1 parts.

[0036] (2) Place the above five raw material components in a high-speed mixer and stir at 1000 rpm for 5 min. Then, extrude the material through a twin-screw extruder, controlling the screw speed at 300 rpm and the screw segment temperatures at 165℃, 170℃, 185℃, and 190℃ respectively. Then, granulate the material by cooling it with 60 cm of water and 10 m of air, and then sieve it through an 80-mesh screen to remove fine powder. Finally, place it in an environment of -0.08 MPa and 70℃ and dry it for 2 h to obtain modified TPU granules.

[0037] Comparative Example 1 This comparative example does not introduce the VO2@3GO complex system. The raw material formulation is (by mass): ①TPU base material (model 1185A): 99.5 parts; ② Antioxidant (1076): 0.2 parts; ③ Light stabilizer (UV-3808PP5): 0.1 parts; ④ Lubricant (zinc stearate): 0.2 parts.

[0038] The above raw materials were placed in a high-speed mixer and stirred at 1000 rpm for 5 minutes. The mixture was then melt-blended using a twin-screw extruder with the temperature range controlled at 180-195℃. The mixture was then conventionally air-cooled and pelletized, and dried at 80℃ for 3 hours to obtain TPU granules.

[0039] Comparative Example 2 This comparative example introduces a VO2@3GO composite system where all raw materials were untreated. The raw material formulation is as follows (by mass): ①TPU base material (model 1185A): 75 parts; ②VO2@3GO complex system: 22 samples; The difference between this VO2@3GO composite system and the VO2@3GO composite system in Example 1 is that VO2 nanopowder and 3GO are used directly instead of modified VO2 nanopowder and GQDs@3GO. ③ Antioxidant (1076): 0.3 parts; ④ Light stabilizer (UV-3808PP5): 0.3 parts; ⑤ Lubricant (zinc stearate): 0.2 parts.

[0040] The above raw materials were placed in a high-speed mixer and stirred at 1500 rpm for 10 minutes. Then, the mixture was extruded through a twin-screw extruder with the screw speed controlled at 300 rpm and the screw section temperatures set at 160℃, 175℃, 185℃, and 195℃ respectively. The material was then granulated by cooling in water at 80 cm and air at 15 m, and then sieved through an 80-mesh screen to remove fine powder. Finally, the mixture was dried in an environment of -0.08 MPa and 80℃ for 4 hours to obtain modified TPU granules.

[0041] Comparative Example 3 This comparative example introduces a VO2@3GO complex system with VO2 as a single modification. The raw material formulation is as follows (by mass): ①TPU base material (model 1185A): 75 parts; ②VO2@3GO complex system: 22 samples; The difference between this VO2@3GO composite system and the VO2@3GO composite system in Example 1 is that the modified VO2 nanopowder is only modified by a silane coupling agent and is not modified by maleic anhydride. ③ Antioxidant (1076): 0.3 parts; ④ Light stabilizer (UV-3808PP5): 0.3 parts; ⑤ Lubricant (zinc stearate): 0.2 parts.

[0042] The above raw materials were placed in a high-speed mixer and stirred at 1500 rpm for 10 minutes. Then, the mixture was extruded through a twin-screw extruder with the screw speed controlled at 300 rpm and the screw section temperatures set at 160℃, 175℃, 185℃, and 195℃ respectively. The material was then granulated by cooling in water at 80 cm and air at 15 m, and then sieved through an 80-mesh screen to remove fine powder. Finally, the mixture was dried in an environment of -0.08 MPa and 80℃ for 4 hours to obtain modified TPU granules.

[0043] Comparative Example 4 This comparative example is a conventional TPU phase change material proposed in the background art, with the following raw material formulation (by mass): ①TPU base material (model 1185A): 80 parts; ② Phase change metal oxide powder (unmodified VO2): 5 parts; ③ Organic phase change material (paraffin): 8 parts; ④ Thermally conductive powder (graphite): 10 parts; ⑤ Amphiphilic dispersant: 2 parts; ⑥ Antioxidant (1076): 0.3 parts.

[0044] The above raw materials are mixed and stirred at 1200 rpm for 10 minutes. The mixture is then melt-blended using a twin-screw extruder with the temperature controlled within the range of 170-190℃. The mixture is then granulated and dried to obtain TPU phase change material.

[0045] Test case The TPU materials prepared in Examples 1-3 and Comparative Examples 1-4 were used as samples, and their different properties were measured according to different methods as shown in Table 1 below. The measurement results are summarized in Table 2: Table 1 Test methods for different performance levels

[0046] Table 2. Material property test results of different samples

[0047] The material performance results obtained from Table 2 above show that, compared with the TPU phase change materials in Comparative Examples 1-4 that did not introduce an equivalent VO2@3GO composite system or existing TPU, Examples 1-3, which use the VO2@3GO composite-modified granulated TPU proposed in this invention, are significantly superior to the samples in Comparative Examples 1-4 in terms of thermal conductivity, flame retardancy rating, yellowing index, and tensile strength. This indicates that the VO2@3GO composite-modified granulated TPU and its preparation method proposed in this invention can solve the problems of insufficient performance of existing TPU materials, such as easy yellowing and low flame retardancy. This modified TPU material has a stronger comprehensive performance and can be more widely used in more high-performance technical fields.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A VO2@3GO composite modified pelletized TPU, characterized in that, According to mass parts, including 70-90 parts of TPU base material, 5-25 parts of VO2@3GO composite system, 0.1-1 part of antioxidant, 0.1-0.5 part of light stabilizer, 0.1-0.5 part of lubricant; The VO2@3GO composite system comprises modified VO2 nano powder and GQDs grafted 3GO, and a double-functional group modified composite interface layer is formed on the surface of the modified VO2 nano powder by silane coupling agent and maleic anhydride.

2. The VO2@3GO composite modified pelletized TPU according to claim 1, wherein, The modified VO2 nano powder is obtained by pretreatment of VO2 nano powder, and the pretreatment process is as follows: A1 Take VO2 nano powder with a particle size of 50-200 nm and place it in a vacuum dryer at 60-100℃; A2 Then add the VO2 nano powder into the hydrogen peroxide solution, immerse it, and place it in a 65-75℃ stirring bath for soaking, then wash it with deionized water, and then place it in a vacuum dryer at 80-90℃; A3 Then take 5 parts of VO2 nano powder and add it to anhydrous ethanol, ultrasonic dispersion, then add 0.2-1.5 parts of silane coupling agent and 0.3-0.6 parts of maleic anhydride, and place it in a 70-80℃ reflux reactor for 4-5 hours, then centrifugal dry to obtain the modified VO2 nano powder.

3. The VO2@3GO composite modified pelletized TPU according to claim 2, characterized in that, In step A2, before immersion, control the solid-liquid ratio to be 8-12:1; stir and soak for 2-3 hours, and then wash with deionized water until neutral.

4. The VO2@3GO composite modified pelletized TPU according to claim 2, wherein, In step A3, before ultrasonic dispersion, control the solid-liquid ratio to be 6-10:1; ultrasonic dispersion for 30-45 minutes, and reflux reaction for 4-5 hours.

5. The VO2@3GO composite modified pelletized TPU according to claim 1, wherein, The GQDs grafted 3GO is obtained by pretreatment of triethylene glycol diisooctanoate, and the pretreatment process is as follows: B1 Add 15-18 parts of triethylene glycol diisooctanoate to a solvent, stir and dissolve, then add 0.2-1.2 parts of amino-functionalized graphene quantum dots with a particle size of 2-5 nm, place it in a 85-95℃ stirring reactor, and distill under reduced pressure until the solvent is completely removed to obtain the GQDs grafted 3GO.

6. The VO2@3GO composite modified pelletized TPU according to claim 5, characterized in that, In step B1, the solid-liquid ratio of triethylene glycol diisooctanoate to solvent is 3-8:1; stir and react for 6-8 hours.

7. The VO2@3GO composite modified pelletized TPU according to claim 1, wherein, The preparation method of the VO2@3GO composite system is as follows: C1 Take 3-8 parts of modified VO2 nano powder, 15-20 parts of GQDs grafted 3GO, 0.8-2 parts of phosphorus-nitrogen flame retardant synergist, and 0.2-0.6 parts of composite anti-deformation agent, mix them, first disperse them at 2000-5000 rpm for 15-180 minutes, and then grind them to obtain a VO2@3GO mixture; C2 Place the VO2@3GO mixture in a 40-60℃ aging oven for 12-48 hours to obtain the VO2@3GO composite system.

8. The VO2@3GO composite modified pelletized TPU according to claim 7, characterized in that, The phosphorus-nitrogen flame retardant synergist comprises ammonium polyphosphate and melamine cyanurate in a mass ratio of 2:08-1.2; the composite anti-deformation agent comprises a hindered phenol antioxidant and an ultraviolet absorber in a mass ratio of 3:1.8-2.

2.

9. A process for the preparation of VO2@3GO composite modified pelletized TPU as claimed in any one of claims 1 to 8, wherein the process comprises the steps of: a) mixing the VO2@3GO composite with the TPU; b) pelletizing the mixture of step (a) to obtain the VO2@3GO composite modified pelletized TPU. The method comprises the following steps: S1 Mix the TPU base material with the VO2@3GO composite system, antioxidant, light stabilizer, and lubricant, and stir them at a speed of 800-2000 rpm to obtain a premix; S2 The premix is put into a twin-screw extruder for melt blending treatment, and the temperature is controlled by stages, and the screw temperature is controlled to be 160-165 DEG C, 170-180 DEG C, 185-190 DEG C, 190-200 DEG C in turn. S3 After extrusion, underwater air cooling is adopted for pelletizing, and the pelletized granules are classified and screened, and then dried to obtain the VO2@3GO composite modified pelletized TPU.

10. The preparation method of VO2@3GO composite modified granulated TPU according to claim 9, characterized in that, In step S3, the temperature is first lowered by 50-100 cm underwater, and then the pelletizing is performed by 10-20 m air cooling; Then, the large particles are removed by passing through a 10-mesh screen, and then the fine powder is removed by passing through an 80-mesh screen; Then, it is placed in an environment of-0.09 to-0.08 MPa and 70-90 DEG C, and dried for 2-8 h to obtain the VO2@3GO composite modified pelletized TPU.

Images