A graphene nanocomposite and its preparation method

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a graphene nanocomposite and a preparation method thereof. The composition of the graphene nanocomposite includes graphite powder, APTES, polyvinyl alcohol, nano-TiO2, polyethylene glycol diol, trimethylolpropane, and isocyanate; the specific preparation steps of the graphene nanocomposite are as follows: S1: Preparation of graphene oxide; S2: Introduction of amino silyl groups into graphene oxide; S3: Grafting of polyvinyl alcohol and nano-titanium dioxide; S4: In-situ polymerization of graft-modified graphene oxide and polyurethane polyol to obtain the graphene nanocomposite; the present invention enhances the dispersion of graphene in the polyurethane matrix through APTES functionalization and PVA grafting to prevent agglomeration; APTES forms covalent bonds with polyurethane to enhance interfacial bonding; PVA increases steric hindrance to improve toughness; TiO2 nanoparticles are stably dispersed to improve impact resistance and tensile strength.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and specifically relates to a graphene nanocomposite material and a preparation method thereof. Background Art

[0002] Since graphene was first successfully exfoliated in 2004, this material, which consists of carbon atoms connected by sp 2 Two-dimensional single-layer materials formed by close hybrid arrangement have quickly become the forefront of nanomaterial research due to their excellent physical, chemical and mechanical properties. Graphene not only has an extremely high specific surface area, excellent electrical and thermal conductivity, but also exhibits excellent mechanical strength and flexibility. However, pure graphene still faces some limitations in practical applications, such as difficult processing, easy agglomeration and limited functionalization. Therefore, compounding graphene with other materials to prepare graphene-based nanocomposites has become an important strategy to improve its comprehensive performance and broaden its application areas. Although graphene has many excellent properties, during the preparation process, single-layer graphene usually inevitably introduces certain defects. These defects may affect the performance of graphene to a certain extent. However, the appropriate introduction of defects has a positive effect on the preparation and performance improvement of graphene-based nanocomposites, and can effectively improve the interfacial interaction between graphene and the matrix material, thereby enhancing the comprehensive performance of the material.

[0003] Polyurea is a type of polymer material formed by the reaction of isocyanate and amine. It is widely used in protective coatings and high-performance elastomeric materials due to its excellent wear resistance, chemical corrosion resistance and high elasticity. Compared with polyurethane, polyurea system does not contain ester bonds, so it is less sensitive to moisture and exhibits better water resistance and chemical resistance. Polyurethane is a polymer material formed by the reaction of isocyanate and polyol. It has a variety of physical forms and good mechanical properties, wear resistance and flexibility. It is widely used in building materials, automotive parts, foam plastics and coatings. Introducing graphene into polyurea or polyurethane matrix can significantly enhance the mechanical strength of the composite material and improve its electrical conductivity and thermal conductivity. In addition, the lamellar structure of graphene has an excellent shielding effect, which significantly improves the composite material in terms of UV resistance, fire resistance and gas barrier properties. For example, graphene can effectively block the penetration of oxygen and water vapor, thereby greatly improving the weather resistance and anti-aging properties of the material. In the development of polyurea or polyurethane-based graphene nanocomposites, the strong van der Waals forces between graphene sheets easily lead to sheet agglomeration, which in turn affects the performance of the material. Summary of the invention

[0004] In view of the defects of the prior art, the object of the present invention is to provide a graphene nanocomposite material and a preparation method thereof.

[0005] The technical effects of the present invention are achieved through the following technical solutions: A preparation method of a graphene nanocomposite, the composition of the graphene nanocomposite includes graphite powder, APTES, polyvinyl alcohol, nano-TiO2, polyethylene glycol diol, trimethylolpropane, and isocyanate;

[0006] Preferably, the specific preparation steps of the graphene nanocomposite are as follows:

[0007] S1: Preparation of graphene oxide; Graphene oxide is prepared by the improved Hummers method;

[0008] S2: Introduction of amino silyl groups into graphene oxide;

[0009] S3: Grafting of polyvinyl alcohol and nano-titanium dioxide; Through the action of initiator ammonium persulfate, polyvinyl alcohol is grafted onto the graphene oxide introduced with amino silyl groups in step S2, and then surface-modified nano-TiO2 is introduced;

[0010] S4: In-situ polymerization grafting modification of graphene oxide and polyurethane polyol to obtain a graphene nanocomposite; By selecting hydrophilic polyol polyethylene glycol diol, adding dibutyltin dilaurate catalyst and trimethylolpropane crosslinking agent, a graphene nanocomposite is prepared.

[0011] Preferably, in step S1, the specific preparation steps of the graphene oxide are as follows:

[0012] A1: Add graphite powder to a flask, slowly add concentrated sulfuric acid and concentrated phosphoric acid, control the reaction temperature at 0-5°C, stir and mix evenly, control the temperature to 10°C, slowly add potassium permanganate, after adding, raise the temperature to 35-40°C, stir and react for 12-24h, after the reaction is completed, slowly add deionized water to dilute, then add hydrogen peroxide to terminate the reaction, centrifuge at 8000rpm for 10min, wash repeatedly with deionized water and 1M HCl solution for 3 times, and dry at 60°C to constant weight to obtain graphene oxide;

[0013] Preferably, in step A1, the dosage ratio of the graphite powder, concentrated sulfuric acid and concentrated phosphoric acid is 1g:24mL:3mL; the dosage ratio of the potassium permanganate, deionized water, hydrogen peroxide and graphite powder is 3g:80-100mL:5-6mL:1g;

[0014] Preferably, in step S2, the introduction of the amino silyl groups, the specific preparation steps are as follows:

[0015] B1: Disperse the graphene oxide prepared in step A1 in absolute ethanol, and ultrasonically treat it at 200 W for 30 - 60 min to obtain a graphene oxide dispersion; slowly add 3 - aminopropyltriethoxysilane to the graphene oxide dispersion, control the temperature to 0 - 5 °C and continuously stir. After the addition is completed, raise the temperature to 80 °C and continuously stir for 12 - 24 h. After the reaction is completed, cool it to room temperature, centrifuge at 8000 rpm for 10 min, wash it 5 times repeatedly with absolute ethanol, and vacuum - dry it at 50 °C to constant weight to obtain modified graphene oxide;

[0016] Preferably, in step B1, the dosage ratio of the graphene oxide, absolute ethanol, and 3 - aminopropyltriethoxysilane is 5 mg: 1 - 2 mL: 0.05 - 0.1 mL;

[0017] Preferably, in step S3, the grafting of polyvinyl alcohol and nano - titanium dioxide is specifically prepared as follows:

[0018] C1: Add polyvinyl alcohol to 20 times the mass of deionized water, raise the temperature to 90 °C, and stir until completely dissolved to obtain a transparent polyvinyl alcohol solution; add the modified graphene oxide prepared in step B1 to deionized water, ultrasonically stir at 200 W for 30 min, and disperse it evenly to obtain a modified graphene oxide solution;

[0019] C2: Slowly add the modified graphene oxide solution in step C1 to the polyvinyl alcohol solution, control the temperature to 60 °C, add a sodium persulfate solution with a concentration of 0.025 g / mL, adjust the pH to 3.5 with HCl solution, and continuously stir and react for 4 - 6 h. After the reaction is completed, cool it to room temperature, centrifuge at 8000 rpm for 10 min, wash it 5 times repeatedly with deionized water, and vacuum - dry it at 50 °C to constant weight to obtain grafted graphene oxide;

[0020] C3: Add TiO2 to absolute ethanol, ultrasonically treat it at 200 W for 30 min, and after dispersing it evenly, add KH - 570 and acetic acid, and stir and react at 60 °C for 2 h. Centrifuge at 8000 rpm for 10 min, wash it 3 times repeatedly with absolute ethanol, and vacuum - dry it at 60 °C to constant weight to obtain modified TiO2;

[0021] C4: Add the modified TiO2 prepared in step C3 to 50 times the mass of deionized water, ultrasonically treat it to disperse it evenly to obtain a modified TiO2 suspension; add the grafted graphene oxide prepared in step C2 to deionized water, ultrasonically treat it to disperse it evenly, prepare a concentration of 5 mg / mL, and then slowly add it to the modified TiO2 suspension, stir and react at room temperature for 1 - 2 h, centrifuge at 6000 rpm for 10 min, wash it with deionized water, and vacuum - dry it at 50 °C to constant weight to obtain composite graphene oxide;

[0022] Preferably, in step C1, the dosage ratio of the modified graphene oxide to deionized water is 5 mg: 1 mL; in step C2, the volume dosage ratio of the polyvinyl alcohol solution, the modified graphene oxide solution and the ammonium persulfate solution is 10 - 12 mL: 5 - 6 mL: 1 mL; in step C3, the dosage ratio of TiO2, absolute ethanol, KH-570 and acetic acid is 2 g: 100 mL: 2 - 2.5 mL: 1 - 1.2 mL; in step C4, the mass ratio of the modified TiO2 to the grafted graphene oxide is 4:1;

[0023] Preferably, in step S4, the specific preparation steps of the in-situ polymerization reaction are as follows:

[0024] D1: Add the composite graphene oxide prepared in step C4 into dimethylformamide, and perform ultrasonic treatment at 200 W for 30 min to disperse evenly, obtaining a composite graphene oxide dispersion; dissolve polyethylene glycol diol in dimethylformamide, and stir to dissolve evenly, obtaining a polyethylene glycol diol solution;

[0025] D2: Add dibutyltin dilaurate and trimethylolpropane into the polyethylene glycol diol solution prepared in step D1. After mixing evenly, slowly add the composite graphene oxide dispersion, perform ultrasonic treatment to disperse evenly, slowly add isocyanate, control the reaction temperature to 60 - 80 °C, stir and react for 2 - 4 h, then cure at 60 - 80 °C for 6 - 12 h, and vacuum dry at 60 °C to constant weight to obtain a graphene nanocomposite;

[0026] Preferably, in step D1, the dosage ratio of the composite graphene oxide to dimethylformamide is 8 - 10 mg: 1 mL; the dosage ratio of the polyethylene glycol diol to dimethylformamide is 0.8 - 1 g: 5 mL;

[0027] Preferably, in step D2, the dosage ratio of dibutyltin dilaurate, trimethylolpropane, the polyethylene glycol diol solution, the composite graphene oxide dispersion and isocyanate is 0.06 - 0.1 g: 0.2 - 0.5 g: 50 mL: 50 mL: 5 g.

[0028] The beneficial effects of the present invention are as follows:

[0029] The present invention effectively enhances the dispersion of graphene in the polyurethane matrix through the functionalization treatment with 3-aminopropyltriethoxysilane (APTES) and the grafting of polyvinyl alcohol (PVA), and solves the agglomeration phenomenon caused by the strong van der Waals force between graphene sheets. Specifically, APTES introduces amino-silyl groups onto the graphene surface through siloxane bonds. These amino groups form steric hindrance on the surface of the graphene sheets, disrupting the π-π stacking and strong van der Waals force between the graphene sheets and hindering the re-stacking and agglomeration of the sheets. At the same time, the amino-silyl groups can form covalent bonds with the isocyanate groups in the polyurethane matrix, significantly enhancing the interfacial bonding strength between graphene and polyurethane. The hydroxyl groups of PVA interact with the amino-silyl groups on the graphene surface and the polyurethane segments through hydrogen bonds, further enhancing the dispersion of graphene in the polymer matrix and strengthening the interfacial bonding of the composite material. In addition, PVA forms a polymer coating layer on the surface of the graphene sheets, increasing steric hindrance and hydrogen bond interactions, preventing direct contact between the graphene sheets, and reducing the agglomeration caused by van der Waals force. The flexibility and crosslinkability of the PVA segments contribute to improving the toughness and ductility of the composite material and avoiding the increase in brittleness caused by graphene agglomeration. The present invention further stabilizes the dispersion state of graphene in the polyurethane matrix by introducing TiO2 nanoparticles. Although the TiO2 nanoparticles mainly endow the composite material with excellent photocatalytic and antibacterial properties, their appropriate addition and uniform distribution synergistically act with the high strength of graphene, enhancing the impact resistance and tensile strength of the composite material.

[0030] During the synthesis of polyurethane, the functionalized graphene directly participates in the polymerization reaction due to its surface active groups, ensuring the uniform dispersion of graphene in the polyurethane matrix. Trimethylolpropane is added as a multifunctional crosslinking agent to form a highly crosslinked polyurethane network. During the in-situ polymerization process, graphene is "fixed" in the polyurethane network, preventing its agglomeration during the curing process. The introduction of the crosslinking agent increases the crosslinking density of polyurethane, enhances the physical and chemical bonding between graphene and the matrix, and improves the overall mechanical properties and thermal stability of the composite material, enabling it to maintain good performance in high-temperature environments.

[0031] In summary, the present invention effectively solves the problem of easy agglomeration of graphene in the polyurethane matrix through the synergistic effects of APTES functionalization, PVA grafting, and TiO2 nanoparticles. The functionalized graphene forms covalent bonds with the polyurethane chains, enhancing the interfacial bonding. The introduction of PVA improves the dispersion of graphene and the toughness of the composite material. The TiO2 nanoparticles not only endow the material with photocatalytic and antibacterial functions but also further enhance the mechanical properties. Brief Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a graph of the flexural test results of the graphene nanocomposites prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention;

[0034] Figure 2 It is a graph of the impact test results of the graphene nanocomposites prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention;

[0035] Figure 3 It is a graph of the thermogravimetric test results of the graphene nanocomposites prepared in Example 2 and Comparative Examples 1-3 of the present invention. Detailed implementation manners

[0036] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. It should be noted that unless otherwise specified, the raw materials involved in the present invention are purchased through conventional commercial channels.

[0037] Example 1: A preparation method of a graphene nanocomposite, the composition of the graphene nanocomposite includes graphite powder, APTES, polyvinyl alcohol, nano-TiO2, polyethylene glycol diol, trimethylolpropane and isocyanate;

[0038] The specific preparation steps of the graphene nanocomposite are as follows:

[0039] A1: Add 10 g of graphite powder to a flask, slowly add 240 mL of concentrated sulfuric acid and 30 mL of concentrated phosphoric acid, control the reaction temperature at 5 °C, stir and mix evenly, control the temperature to 10 °C, slowly add 30 g of potassium permanganate, after the addition is completed, raise the temperature to 35 °C, stir and react for 24 h, after the reaction is completed, slowly add 800 mL of deionized water for dilution, then add 50 mL of hydrogen peroxide to terminate the reaction, centrifuge at 8000 rpm for 10 min, wash repeatedly with deionized water and 1 M HCl solution for 3 times, and dry at 60 °C to constant weight to obtain graphene oxide;

[0040] B1: Disperse 1000 mg of graphene oxide prepared in step A1 in 2000 mL of absolute ethanol, and ultrasonically treat it at 200 W for 30 min to obtain a graphene oxide dispersion; slowly add 20 mL of 3-aminopropyltriethoxysilane to the graphene oxide dispersion, control the temperature to 5 °C and continuously stir. After the addition is completed, raise the temperature to 80 °C and continuously stir for 12 h. After the reaction is completed, cool it to room temperature, centrifuge at 8000 rpm for 10 min, wash it 5 times repeatedly with absolute ethanol, and vacuum dry it at 50 °C to constant weight to obtain modified graphene oxide;

[0041] C1: Add 20 g of polyvinyl alcohol to 400 mL of deionized water, raise the temperature to 90 °C, and stir until completely dissolved to obtain a transparent polyvinyl alcohol solution; add 1000 mg of the modified graphene oxide prepared in step B1 to 200 mL of deionized water, ultrasonically stir it at 200 W for 30 min to disperse it evenly to obtain a modified graphene oxide solution;

[0042] C2: Slowly add 200 mL of the modified graphene oxide solution in step C1 to 400 mL of the polyvinyl alcohol solution, control the temperature to 60 °C, add 35 mL of a 0.025 g / mL sodium persulfate solution, adjust the pH to 3.5 with HCl solution, continuously stir and react for 4 h. After the reaction is over, cool it to room temperature, centrifuge at 8000 rpm for 10 min, wash it 5 times repeatedly with deionized water, and vacuum dry it at 50 °C to constant weight to obtain grafted graphene oxide;

[0043] C3: Add 10 g of TiO2 to 500 mL of absolute ethanol, ultrasonically treat it at 200 W for 30 min. After dispersing it evenly, add 11 mL of KH-570 and 5.5 mL of acetic acid, stir and react at 60 °C for 2 h, centrifuge at 8000 rpm for 10 min, wash it 3 times repeatedly with absolute ethanol, and vacuum dry it at 60 °C to constant weight to obtain modified TiO2;

[0044] C4: Add 4 g of the modified TiO2 prepared in step C3 to 200 mL of deionized water, ultrasonically treat it to disperse it evenly to obtain a modified TiO2 suspension; add 1000 mg of the grafted graphene oxide prepared in step C2 to 200 mL of deionized water, ultrasonically treat it to disperse it evenly, prepare a concentration of 5 mg / mL, and then slowly add it to the modified TiO2 suspension, stir and react at room temperature for 1 h, centrifuge at 6000 rpm for 10 min, wash it with deionized water, and vacuum dry it at 50 °C to constant weight to obtain composite graphene oxide;

[0045] D1: Add 1000 mg of the composite graphene oxide prepared in step C4 into 125 mL of dimethylformamide, and perform ultrasonic treatment at 200 W for 30 min to disperse evenly, obtaining a composite graphene oxide dispersion; dissolve 32 g of polyethylene glycol diol in 200 mL of dimethylformamide, and stir to dissolve evenly to obtain a polyethylene glycol diol solution;

[0046] D2: Add 0.24 g of dibutyltin dilaurate and 0.8 g of trimethylolpropane into the 200 mL of polyethylene glycol diol solution prepared in step D1. After mixing evenly, slowly add 200 mL of the composite graphene oxide dispersion, perform ultrasonic treatment to disperse evenly, slowly add 20 g of isocyanate, control the reaction temperature to 60 °C, stir and react for 2 h, then cure at 60 °C for 12 h, and vacuum dry at 60 °C to constant weight to obtain a graphene nanocomposite.

[0047] Example 2: A preparation method of a graphene nanocomposite, the composition of the graphene nanocomposite includes graphite powder, APTES, polyvinyl alcohol, nano-TiO2, polyethylene glycol diol, trimethylolpropane, and isocyanate;

[0048] The specific preparation steps of the graphene nanocomposite are as follows:

[0049] A1: Add 10 g of graphite powder into a flask, slowly add 240 mL of concentrated sulfuric acid and 30 mL of concentrated phosphoric acid, control the reaction temperature at 0 °C, stir and mix to disperse evenly, control the temperature to 10 °C, slowly add 30 g of potassium permanganate, after adding, raise the temperature to 40 °C, stir and react for 24 h. After the reaction is completed, slowly add 1000 mL of deionized water to dilute, then add 600 mL of hydrogen peroxide to terminate the reaction, centrifuge at 8000 rpm for 10 min, and repeat washing 3 times with deionized water and 1 M HCl solution, and dry at 60 °C to constant weight to obtain graphene oxide;

[0050] B1: Disperse 1000 mg of the graphene oxide prepared in step A1 in 1000 mL of absolute ethanol, perform ultrasonic treatment at 200 W for 60 min to obtain a graphene oxide dispersion; slowly drop 10 mL of 3-aminopropyltriethoxysilane into the graphene oxide dispersion, control the temperature at 0 °C and continuously stir. After dropping, raise the temperature to 80 °C and continuously stir for 24 h. After the reaction is completed, cool to room temperature, centrifuge at 8000 rpm for 10 min, and repeat washing 5 times with absolute ethanol, and vacuum dry at 50 °C to constant weight to obtain modified graphene oxide;

[0051] C1: Add 20 g of polyvinyl alcohol to 400 mL of deionized water, raise the temperature to 90 °C, and stir until completely dissolved to obtain a transparent polyvinyl alcohol solution; add 1000 mg of modified graphene oxide prepared in step B1 to 200 mL of deionized water, perform ultrasonic stirring at 200 W for 30 min, disperse evenly to obtain a modified graphene oxide solution;

[0052] C2: Slowly add 200 mL of the modified graphene oxide solution in step C1 to 400 mL of the polyvinyl alcohol solution, control the temperature to 60 °C, add 40 mL of a 0.025 g / mL sodium persulfate solution, adjust the pH to 3.5 with HCl solution, continuously stir and react for 6 h. After the reaction, cool to room temperature, centrifuge at 8000 rpm for 10 min, wash repeatedly with deionized water 5 times, and vacuum dry at 50 °C to constant weight to obtain grafted graphene oxide;

[0053] C3: Add 10 g of TiO2 to 500 mL of absolute ethanol, perform ultrasonic treatment at 200 W for 30 min. After dispersing evenly, add 10 mL of KH-570 and 5 mL of acetic acid, stir and react at 60 °C for 2 h, centrifuge at 8000 rpm for 10 min, wash repeatedly with absolute ethanol 3 times, and vacuum dry at 60 °C to constant weight to obtain modified TiO2;

[0054] C4: Add 4 g of the modified TiO2 prepared in step C3 to 200 mL of deionized water, perform ultrasonic treatment to disperse evenly to obtain a modified TiO2 suspension; add 1000 mg of the grafted graphene oxide prepared in step C2 to 200 mL of deionized water, perform ultrasonic treatment to disperse evenly, prepare a concentration of 5 mg / mL, and then slowly add it to the modified TiO2 suspension. Stir and react at room temperature for 2 h, centrifuge at 6000 rpm for 10 min, wash with deionized water, and vacuum dry at 50 °C to constant weight to obtain composite graphene oxide;

[0055] D1: Add 1000 mg of the composite graphene oxide prepared in step C4 to 100 mL of dimethylformamide, perform ultrasonic treatment at 200 W for 30 min, disperse evenly to obtain a composite graphene oxide dispersion; dissolve 40 g of polyethylene glycol diol in 200 mL of dimethylformamide, stir and dissolve evenly to obtain a polyethylene glycol diol solution;

[0056] D2: Add 0.4 g of dibutyltin dilaurate and 2 g of trimethylolpropane to 200 mL of the polyethylene glycol diol solution prepared in step D1. After mixing evenly, slowly add 200 mL of the composite graphene oxide dispersion, perform ultrasonic treatment to disperse evenly, slowly add 20 g of isocyanate, control the reaction temperature to 80 °C, stir and react for 4 h, then cure at 80 °C for 12 h, and vacuum dry at 60 °C to constant weight to obtain a graphene nanocomposite.

[0057] Example 3: A preparation method of a graphene nanocomposite, the composition of the graphene nanocomposite includes graphite powder, APTES, polyvinyl alcohol, nano-TiO2, polyethylene glycol diol, trimethylolpropane and isocyanate;

[0058] The specific preparation steps of the graphene nanocomposite are as follows:

[0059] A1: Add 10 g of graphite powder into a flask, slowly add 240 mL of concentrated sulfuric acid and 30 mL of concentrated phosphoric acid, control the reaction temperature at 4 °C, stir and mix evenly, control the temperature to 10 °C, slowly add 30 g of potassium permanganate, after the addition is completed, raise the temperature to 38 °C, stir and react for 18 h, after the reaction is completed, slowly add 900 mL of deionized water for dilution, then add 550 mL of hydrogen peroxide to terminate the reaction, centrifuge at 8000 rpm for 10 min, wash repeatedly with deionized water and 1M HCl solution for 3 times, and dry at 60 °C to constant weight to obtain graphene oxide;

[0060] B1: Disperse 1000 mg of the graphene oxide prepared in step A1 in 1600 mL of absolute ethanol, perform ultrasonic treatment at 200 W for 50 min to obtain a graphene oxide dispersion; slowly drop 16 mL of 3-aminopropyltriethoxysilane into the graphene oxide dispersion, control the temperature at 4 °C and keep stirring, after the dropping is completed, raise the temperature to 80 °C, keep stirring for 18 h, cool to room temperature after the reaction is completed, centrifuge at 8000 rpm for 10 min, wash repeatedly with absolute ethanol for 5 times, and dry in vacuum at 50 °C to constant weight to obtain modified graphene oxide;

[0061] C1: Add 20 g of polyvinyl alcohol into 400 mL of deionized water, raise the temperature to 90 °C, stir until completely dissolved to obtain a transparent polyvinyl alcohol solution; add 1000 mg of the modified graphene oxide prepared in step B1 into 200 mL of deionized water, perform ultrasonic stirring at 200 W for 30 min to disperse evenly to obtain a modified graphene oxide solution;

[0062] C2: Slowly add 200 mL of the modified graphene oxide solution in step C1 into 396 mL of the polyvinyl alcohol solution, control the temperature at 60 °C, add 33 mL of a 0.025 g / mL sodium persulfate solution, adjust the pH to 3.5 with HCl solution, keep stirring and reacting for 5 h, after the reaction is over, cool to room temperature, centrifuge at 8000 rpm for 10 min, wash repeatedly with deionized water for 5 times, and dry in vacuum at 50 °C to constant weight to obtain grafted graphene oxide;

[0063] C3: Add 10 g of TiO2 into 500 mL of absolute ethanol, and ultrasonically treat it for 30 min at 200 W. After uniform dispersion, add 12.5 mL of KH-570 and 6 mL of acetic acid, stir and react at 60 °C for 2 h, centrifuge at 8000 rpm for 10 min, wash repeatedly with absolute ethanol three times, and vacuum dry at 60 °C until constant weight to obtain modified TiO2;

[0064] C4: Add 4 g of the modified TiO2 prepared in step C3 into 200 mL of deionized water, ultrasonically treat it to disperse evenly to obtain a modified TiO2 suspension; add 1000 mg of the grafted graphene oxide prepared in step C2 into 200 mL of deionized water, ultrasonically treat it to disperse evenly, prepare a solution with a concentration of 5 mg / mL, and then slowly add it to the modified TiO2 suspension. Stir and react at room temperature for 1.5 h, centrifuge at 6000 rpm for 10 min, wash with deionized water, and vacuum dry at 50 °C until constant weight to obtain composite graphene oxide;

[0065] D1: Add 1000 mg of the composite graphene oxide prepared in step C4 into 110 mL of dimethylformamide, ultrasonically treat it for 30 min at 200 W to disperse evenly to obtain a composite graphene oxide dispersion; dissolve 35 g of polyethylene glycol diol in 200 mL of dimethylformamide, stir and dissolve evenly to obtain a polyethylene glycol diol solution;

[0066] D2: Add 0.35 g of dibutyltin dilaurate and 1.5 g of trimethylolpropane into the 200 mL of polyethylene glycol diol solution prepared in step D1, mix evenly, then slowly add 200 mL of the composite graphene oxide dispersion, ultrasonically treat it to disperse evenly, slowly add 20 g of isocyanate, control the reaction temperature to 70 °C, stir and react for 3 h, then cure at 70 °C for 10 h, and vacuum dry at 60 °C until constant weight to obtain a graphene nanocomposite.

[0067] Comparative Example 1: The operation of Comparative Example 1 is basically the same as that of Example 2, except that in Comparative Example 1, graphene oxide is not subjected to APTES functionalization treatment, and the untreated graphene oxide is directly mixed and reacted with polyethylene glycol diol.

[0068] Comparative Example 2: The operation of Comparative Example 2 is basically the same as that of Example 2, except that in Comparative Example 2, APTES-functionalized graphene oxide is used, but no PVA grafting treatment is carried out, and it is directly subjected to in-situ polymerization with polyethylene glycol diol.

[0069] Comparative Example 3: The operation of Comparative Example 3 is basically the same as that of Example 2, except that in Comparative Example 3, TiO2 nanoparticles are not added to the composite material.

[0070] Performance test:

[0071] Tensile test: Fix the nano-graphene composite material samples prepared in Examples 1-3 and Comparative Examples 1-3 in the fixture of a universal material testing machine. Use a tensile speed of 10 mm / min, set the initial tensile force to 0 N, ensure that the sample starts the test without initial stress, start the testing machine, continuously apply a tensile load until the sample breaks, record and calculate the tensile strength and elongation at break. The results are shown in Table 1 below;

[0072] Table 1. Tensile strength test results

[0073]

[0074] As can be seen from the results in Table 1, the nano-graphene composite materials prepared by the present invention have good mechanical properties and certain toughness, and are suitable for high-strength applications; from the results of Example 2 and Comparative Example 1, it can be seen that unfunctionalized graphene oxide may lead to poor dispersion of graphene in the polyurethane matrix, easy agglomeration, resulting in weak interfacial bonding force and lack of interfacial strengthening mechanism, which will reduce the overall mechanical properties of the material, and then lead to lower tensile strength. At the same time, due to the agglomeration of graphene, the ductility of the composite material is poor, resulting in a decrease in elongation at break; from the results of Example 2 and Comparative Example 2, it can be seen that polyvinyl alcohol strengthens the interfacial bonding through hydrogen bonds, forms a coating layer, and increases the dispersion and toughness of graphene; without polyvinyl alcohol grafting, the dispersion of graphene is affected, and there may still be some agglomeration, resulting in the toughness and ductility of the material being affected; from the results of Example 3 and Comparative Example 2, it can be seen that the introduction of TiO2 plays a role in enhancing the dispersion stability and mechanical properties of graphene, and the lack of this synergistic effect leads to a certain degree of influence on the elongation at break and tensile strength of the material.

[0075] Flexural test: Horizontally place the nano-graphene composite material samples prepared in Examples 1-3 and Comparative Examples 1-3 on the support frame of a three-point bending tester. The distance between the fulcrums is 80% of the sample length. Set the bending speed to 1 mm / min, set the initial load to 0 N, and record the flexural strength. The results are as Figure 1 shown.

[0076] From Figure 1It can be seen from the results that the graphene nanocomposite prepared by the present invention has excellent flexural strength; from the results of Example 2 and Comparative Example 1, it can be seen that due to the lack of APTES functionalization, the interfacial bonding between graphene and polyurethane is weak, and the agglomeration of graphene in the matrix is relatively serious, which will lead to poor stress transfer ability of the composite material, and the material is prone to fracture when bent, thus significantly affecting the flexural strength; from the results of Comparative Example 2 and Example 2, it can be seen that due to the lack of polyvinyl alcohol grafting, the flexibility and ductility of the composite material are limited. Although the dispersion and interfacial bonding strength of graphene sheets are improved, without the flexible chain segments and steric hindrance effect of polyvinyl alcohol, the flexural strength is significantly affected; from the results of Comparative Example 3 and the Example, it can be seen that TiO2 improves the mechanical properties of the material through synergistic action with graphene, and its absence leads to a certain degree of influence on the flexural strength.

[0077] Impact test: Vertically install the nano-graphene composite material samples prepared in Examples 1-3 and Comparative Examples 1-3 on the sample fixture of the impact testing machine, ensure that the notch is directly opposite to the impact position, start the testing machine, the pendulum is released to impact the sample, record the energy difference before and after the pendulum impact, calculate the energy absorption capacity of the material, and calculate the impact strength according to the absorbed energy and the cross-sectional area of the sample. The results are as Figure 2 shown.

[0078] From Figure 2 the results, it can be seen that the graphene nanocomposite prepared by the present invention has excellent impact resistance; from the results of Comparative Example 1 and Example 2, it can be seen that without APTES functionalization treatment, graphene agglomerates, resulting in low impact strength of the material; from the results of Comparative Example 2 and Example 2, it can be seen that due to the lack of the synergistic strengthening effect of polyvinyl alcohol grafting, the toughness and dispersion of the material are relatively poor, and the impact strength is affected; from the results of Comparative Example 3 and Example 2, it can be seen that due to the absence of TiO2, the impact strength of the material is slightly affected.

[0079] Thermogravimetric analysis test: Place the graphene nanocomposite materials prepared in Example 2 and Comparative Examples 1-3 in a TGA device, and heat them to 200 °C, 300 °C and 500 °C at a rate of 10 °C / min under a nitrogen atmosphere, and test the mass loss percentage at 200 °C, 300 °C and 500 °C, and record the results as Figure 3 shown.

[0080] From Figure 3It can be seen from the results that the graphene nanocomposite prepared by the present invention has excellent thermal stability and can have a relatively high residue at high temperatures. From the results of Comparative Example 1 and Example 2, it can be seen that the interfacial bonding between graphene without APTES functionalization and polyurethane is weak, which may lead to the agglomeration of graphene sheets, poor dispersion of graphene, and affect the thermal stability. From the results of Comparative Example 2 and Example 2, it can be seen that without grafting with polyvinyl alcohol, the functionalized graphene binds strongly to polyurethane, but lacks the coating effect of polyvinyl alcohol, resulting in a decrease in the dispersion of graphene and the toughness of the composite material, and the thermal decomposition is affected. From the results of Comparative Example 3 and Example 2, it can be seen that the grafting of polyvinyl alcohol improves the dispersion of the composite material, but the absence of TiO2 affects the performance at high temperatures.

[0081] Chemical corrosion resistance test: The graphene nanocomposites prepared in Example 2 and Comparative Examples 1-3 were tested in a 5% NaCl solution at a temperature of 35 ± 2 °C for 168 h, and the mass loss and appearance changes were recorded. The results are shown in Table 2 below.

[0082] Table 2. Chemical corrosion resistance test results of graphene nanocomposites

[0083]

[0084] It can be seen from the results in Table 2 that the graphene nanocomposite prepared by the present invention has excellent chemical corrosion resistance. From the results of Comparative Example 1 and Example 2, it can be seen that due to the poor dispersion of graphene in the matrix and weak interfacial bonding, water and salts are more likely to penetrate into the composite material, resulting in the decomposition of the polyurethane matrix due to corrosion, and further leading to more significant mass loss and appearance changes. From the results of Comparative Example 2 and Example 2, it can be seen that there is a covalent bond between the functionalized graphene oxide and the polyurethane matrix, but without the protection and steric hindrance of the polyvinyl alcohol grafting layer on the graphene sheets, there may still be some agglomeration between the graphene sheets, resulting in an increase in the mass loss of the graphene nanocomposite. From the results of Comparative Example 3 and Example 2, it can be seen that the absence of the stabilizing effect of TiO2 nanoparticles significantly affects the overall corrosion resistance of the composite material.

[0085] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in 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 method for preparing a graphene nanocomposite material, characterized in that: The graphene nanocomposite material comprises graphite powder, APTES, polyvinyl alcohol, nano-TiO2, polyethylene glycol, trimethylolpropane and isocyanate; The specific preparation steps of the graphene nanocomposite material are as follows: S1: Preparation of graphene oxide; Preparation of graphene oxide using a modified Hummers method; S2: introduction of aminosilane groups into graphene oxide; S3: Grafting polyvinyl alcohol and nano-titanium dioxide; through the action of initiator ammonium persulfate, polyvinyl alcohol is grafted onto the graphene oxide introduced with aminosilane groups in step S2, and then the surface-modified nano-TiO2 is introduced; S4: In-situ polymerization and grafting of modified graphene oxide and polyurethane polyol to obtain graphene nanocomposites; The graphene nanocomposite material is prepared by selecting a hydrophilic polyol polyethylene glycol diol, adding a dibutyltin dilaurate catalyst and a trimethylolpropane crosslinking agent; In step S1, the specific preparation steps of the graphene oxide are as follows: A1: Add graphite powder to a flask, slowly add concentrated sulfuric acid and concentrated phosphoric acid, control the reaction temperature, stir and mix to disperse evenly, control the temperature, slowly add potassium permanganate, increase the temperature, stir and react, after the reaction is completed, slowly add deionized water to dilute, then add hydrogen peroxide to terminate the reaction, centrifuge, repeat washing with deionized water and HCl solution for 3 times, dry to constant weight, and obtain graphene oxide; In step A1, the ratio of the amount of graphite powder, concentrated sulfuric acid and concentrated phosphoric acid is 1g:24mL:3mL; the ratio of the amount of potassium permanganate, deionized water, hydrogen peroxide and graphite powder is 3g:80-100mL:5-6mL:1g; in step S2, the introduction of the aminosilane group, the specific preparation steps are as follows: B1: dispersing the graphene oxide prepared in step A1 in anhydrous ethanol, and ultrasonically treating to obtain a graphene oxide dispersion; slowly dropping 3-aminopropyltriethoxysilane into the graphene oxide dispersion, controlling the temperature and continuously stirring, after the dropping is completed, heating up, continuously stirring, cooling to room temperature after the reaction is completed, centrifuging, washing with anhydrous ethanol, and vacuum drying to constant weight to obtain modified graphene oxide; In step B1, the ratio of the amount of graphene oxide, anhydrous ethanol and 3-aminopropyltriethoxysilane is 5 mg: 1-2 mL: 0.05-0.1 mL; In step S3, the grafting of polyvinyl alcohol and nano-titanium dioxide is specifically prepared as follows: C1: adding polyvinyl alcohol to deionized water, raising the temperature, stirring until completely dissolved, and obtaining a transparent polyvinyl alcohol solution; adding the modified graphene oxide prepared in step B1 to deionized water, stirring by ultrasonication, and dispersing uniformly to obtain a modified graphene oxide solution; C2: slowly adding the modified graphene oxide solution in step C1 to the polyvinyl alcohol solution, controlling the temperature, adding sodium persulfate solution, adjusting the pH with HCl solution, and continuously stirring the reaction. After the reaction is completed, cooling to room temperature, centrifuging, washing with deionized water, and vacuum drying to constant weight to obtain grafted graphene oxide; C3: Add TiO2 to anhydrous ethanol, perform ultrasonic treatment, and after uniform dispersion, add KH-570 and acetic acid, stir to react, centrifuge, wash with anhydrous ethanol, and vacuum dry to constant weight to obtain modified TiO2; C4: adding the modified TiO2 prepared in step C3 to deionized water, dispersing it evenly by ultrasonic treatment, and obtaining a modified TiO2 suspension; adding the grafted graphene oxide prepared in step C2 to deionized water, dispersing it evenly by ultrasonic treatment, and then slowly adding the modified TiO2 suspension, stirring the reaction at room temperature, centrifuging, washing with deionized water, and vacuum drying to constant weight to obtain composite graphene oxide; In step C1, the ratio of the amount of the modified graphene oxide to deionized water is 5 mg: 1 mL; in step C2, the volume ratio of the polyvinyl alcohol solution, the modified graphene oxide solution and the ammonium persulfate solution is 10-12 mL: 5-6 mL: 1 mL; in step C3, the ratio of the amount of TiO2, anhydrous ethanol, KH-570 and acetic acid is 2 g: 100 mL: 2-2.5 mL: 1-1.2 mL; in step C4, the mass ratio of modified TiO2 and grafted graphene oxide is 4: 1; In step S4, the specific preparation steps of the in-situ polymerization reaction are as follows: D1: adding the composite graphene oxide prepared in step C4 to dimethylformamide, performing ultrasonic treatment, and dispersing the composite graphene oxide uniformly to obtain a composite graphene oxide dispersion; dissolving polyethylene glycol diol in dimethylformamide, stirring and dissolving the polyethylene glycol diol uniformly to obtain a polyethylene glycol diol solution; D2: adding dibutyltin dilaurate and trimethylolpropane to the polyethylene glycol diol solution prepared in step D1, mixing evenly, slowly adding the composite graphene oxide dispersion, ultrasonically dispersing evenly, slowly adding isocyanate, controlling the reaction temperature, stirring the reaction, curing, and vacuum drying to constant weight to obtain a graphene nanocomposite material; In step D1, the ratio of the composite graphene oxide to dimethylformamide is 8-10 mg:1 mL; the ratio of the polyethylene glycol diol to dimethylformamide is 0.8-1 g:5 mL; and the ratio of the dibutyltin dilaurate, trimethylolpropane, polyethylene glycol diol solution, composite graphene oxide dispersion and isocyanate in step D2 is 0.06-0.1 g:0.2-0.5 g:50 mL:50 mL:5 g.

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