Preparation method of five-membered ring carbonate group grafted modified graphene oxide and preparation of composite material thereof

Abstract

The application discloses a preparation method of graphene oxide grafted with five-membered ring carbonate groups, which comprises the following steps: 1) adding diphenylmethane diisocyanate dropwise into a graphene oxide dispersion solution to perform reaction, so as to obtain graphene oxide intermediate grafted with isocyanate groups; and 2) adding glycerol carbonate dropwise into the graphene oxide intermediate to perform reaction, so as to obtain graphene oxide grafted with five-membered ring carbonate groups. The application further discloses a preparation method of a composite material containing the modified graphene oxide, wherein the modified graphene oxide is uniformly dispersed in a cyclic carbonate active diluent, and then reacts with polyamine and epoxy resin to prepare a hybrid non-isocyanate polyurethane composite material containing the modified graphene oxide. The composite material prepared by the application has very strong physical bonding and chemical bonding effects between the modified graphene oxide and the matrix material, can be uniformly dispersed in the composite material, has good toughness, and has excellent mechanical properties and load transfer capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of graphene-modified composite materials, and particularly relates to a method for preparing five-membered cyclic carbonate group-grafted modified graphene oxide and a non-isocyanate polyurethane composite material containing the modified graphene oxide. Background Art

[0002] With growing public awareness of environmental protection and the need for sustainable development, the use of green and environmentally friendly synthetic routes to prepare polymer materials has attracted widespread attention. Non-isocyanate polyurethanes are polymers synthesized using CO2 as a raw material, completely avoiding the use of toxic isocyanates. Due to the presence of urethane groups and β-hydroxyl groups in their molecular chains, they exhibit excellent wear resistance and chemical resistance. However, due to strong hydrogen bonding within the molecules, chain growth is hindered during the synthesis process, resulting in a low molecular weight and, consequently, poor mechanical properties. Therefore, the modification of non-isocyanate polyurethanes is particularly important.

[0003] In recent years, graphene, an emerging two-dimensional nanocarbon material, has been widely used in polymer modification due to its unique lamellar structure and nanoscale properties, resulting in excellent mechanical properties, chemical stability, and heat resistance. While retaining these advantages, graphene oxide (GO) also possesses surface oxygen-containing functional groups that can interact physically or chemically with the polymer matrix, further improving the material's properties. However, GO's micro-nanoscale size can lead to severe aggregation within the matrix, compromising the composite's performance. Therefore, GO needs to be modified to enhance the interaction between the two.

[0004] Among various graphene oxide modification methods, grafting can significantly improve the interaction between graphene sheets and the polymer matrix. For example, Wan et al. (Wan, Yan-Jun, Tang, Long-Cheng, Carbon, 2014, Vol. 69, pp. 467-480) grafted epoxy resin segments onto the surface of graphene oxide and applied this to reinforced epoxy resins. This approach improved the interaction between the graphene sheets and the matrix to a certain extent, thereby enhancing the mechanical properties of the material. However, this method only strengthens the physical bond between the graphene sheets and the matrix through grafting epoxy segments, and does not result in a stronger chemical bond. Doley et al. (Doley, Simanta, Sarmah, Asish, Sarkar, Chandrama, Polymer International, 2018, Vol. 67, P1062-1069) used amines to modify the surface of graphene oxide and applied it to the modification of non-isocyanate polyurethanes. They relied on the chemical bonding between the graphene sheets and the matrix to improve the mechanical properties of the product. However, due to the poor dispersion of the sheets in the matrix and the increase in cross-linking density, the toughness of the composite material was significantly reduced.

[0005] Therefore, how to apply graphene oxide to non-isocyanate polyurethane through effective methods to give the composite material excellent comprehensive properties requires considering how to surface treat graphene oxide and enhance its bonding with the non-isocyanate polyurethane matrix. However, the existing technology does not provide a corresponding solution. Summary of the Invention

[0006] The present invention addresses the shortcomings of the prior art and practical application needs by providing a method for preparing graphene oxide grafted with five-membered cyclic carbonate groups and a method for preparing a non-isocyanate polyurethane composite material containing the modified graphene oxide. The composite material prepared by this method exhibits strong chemical and physical bonding between the modified graphene oxide and the matrix material, and the graphene sheets are uniformly dispersed in the matrix material, resulting in excellent performance.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing five-membered cyclic carbonate group-grafted modified graphene oxide comprises the following steps:

[0009] 1) Preparation of isocyanate-grafted graphene oxide: adding an organic solvent to a reactor, adding graphene oxide thereto, and ultrasonically dispersing the mixture in a water bath at room temperature for 2-4 hours; then adding diphenylmethane diisocyanate, and ultrasonically dispersing the mixture in a water bath under inert gas protection for 2-5 hours; then heating the water bath to 50-70°C, and continuing the reaction for 10-12 hours to obtain an isocyanate-grafted graphene oxide solution; and washing the product solution to obtain an isocyanate-grafted graphene oxide intermediate.

[0010] 2) Preparation of graphene oxide grafted with pentacyclic carbonate groups: an organic solvent is added to a reactor, the modified graphene oxide intermediate prepared in step 1) is added thereto, and ultrasonic dispersion is carried out in a water bath under inert gas protection for 2 to 4 hours; glycerol carbonate is then added, and ultrasonic dispersion is continued for 0.5 to 1 hour; the temperature is then raised to 50 to 70° C., and the reaction is continued for 24 hours to obtain a graphene oxide solution grafted with pentacyclic carbonate groups; the product solution is washed and dried to obtain graphene oxide grafted with pentacyclic carbonate groups.

[0011] In step 1) or step 2), the inert gas is nitrogen.

[0012] Furthermore, in step 1) or step 2), the organic solvent is selected from any one of N, N-dimethylformamide (DMF), N, N-dimethylacetamide, acetone, tetrahydrofuran, and dimethyl sulfoxide; preferably N, N-dimethylformamide.

[0013] Furthermore, in step 1), the mass ratio of the graphene oxide to the organic solvent is 1:150-500; and in step 2), the mass ratio of the modified graphene oxide intermediate to the organic solvent is 1:500-2000. When the amount of organic solvent used is less than 150, the concentration of graphene oxide in the solution is high, easily causing precipitation, and also hindering the dispersion of diphenylmethane diisocyanate or glycerol carbonate in the system. When the amount of organic solvent used is greater than 500, the concentration of graphene oxide and solvent is too low. When diphenylmethane diisocyanate or glycerol carbonate is used for the reaction, this low concentration may affect the reaction rate. Excessive solvent also increases preparation costs and creates unnecessary difficulties for recovery and post-processing.

[0014] Furthermore, in step 1), the mass ratio of graphene oxide to diphenylmethane diisocyanate is 1:20-100. The reaction between graphene oxide and the isocyanate primarily relies on the reaction between -OH groups and other groups on the graphene oxide surface and -NCO groups on the isocyanate. The molecular weight of this isocyanate is approximately 250 g / mol. Too low an isocyanate content results in a small amount of reaction with the organic functional groups on the graphene oxide surface, preventing effective grafting. Too high an isocyanate content may lead to isocyanate aggregation on the graphene surface.

[0015] Furthermore, in step 2), the mass ratio of the modified graphene oxide intermediate to glycerol carbonate is 1:0.5-4. The primary consideration is that the amount of glycerol carbonate should be in excess to ensure complete reaction of the isocyanate groups on the surface of the graphene oxide intermediate. Considering extreme conditions, if the intermediate graphene is entirely composed of diphenylmethane diisocyanate (a single molecule reacts with only one NCO group), only a mass ratio of 0.5 glycerol carbonate to diphenylmethane diisocyanate is required. In practice, other groups may also be present on the surface of the intermediate while also oxidizing the graphene carbon layer, so a lower limit of 0.5 glycerol carbonate is acceptable. An upper limit of 4 glycerol carbonate is sufficient to ensure an excess of glycerol carbonate, but excessive excess can make subsequent washing and drying of the modified graphene oxide inconvenient, so it should be avoided.

[0016] Furthermore, in step 1) or step 2), the washing method is: first centrifuging the product, washing it with N, N-dimethylformamide for 3 to 5 times, and then washing it with dichloromethane for 5 to 8 times.

[0017] The chemical reaction process of the five-membered cyclic carbonate group grafted modified graphene oxide of the present invention is as follows:

[0018]

[0019] Based on the prepared five-membered cyclic carbonate group grafted modified graphene oxide, the present invention also provides a method for preparing a non-isocyanate polyurethane composite material containing the modified graphene oxide, the method comprising the following steps:

[0020] A. Add the modified graphene oxide to the cyclic carbonate active diluent and heat in a water bath and ultrasonically disperse for 2 to 4 hours;

[0021] B. adding a polyamine to the solution of step A, reacting at 60-100° C. for 2-8 hours to obtain a prepolymer containing modified graphene oxide;

[0022] C. Add epoxy resin to the prepolymer in step B and mix evenly, and cure at 100° C. for 1 to 2 hours to finally obtain a non-isocyanate polyurethane composite material containing modified graphene oxide.

[0023] Furthermore, in step A, the cyclic carbonate reactive diluent used is one or more of ethylene carbonate, propylene carbonate, ethylene glycol diglycidyl ether type cyclic carbonate, 1,4-butanediol diglycidyl ether type cyclic carbonate, hexanediol diglycidyl ether type cyclic carbonate, polyethylene glycol diglycidyl ether type cyclic carbonate, and polypropylene glycol diglycidyl ether type cyclic carbonate.

[0024] Furthermore, the number average molecular weight of the polyethylene glycol diglycidyl ether type cyclic carbonate is 600 to 2000 g / mol; the number average molecular weight of the polypropylene glycol diglycidyl ether type cyclic carbonate is 500 to 2500 g / mol.

[0025] Furthermore, in step B, the polyamine used is one or more of ethylenediamine, 1,3-propylenediamine, 1,6-hexanediamine, polyetheramine D230, polyetheramine T403, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0026] Furthermore, in step C, the epoxy resin used is one or more of bisphenol A epoxy resin E51, E44, E54, bisphenol F epoxy resin NPEF170 or novolac epoxy resin F-44.

[0027] Furthermore, the mass ratio of the modified graphene oxide, the cyclic carbonate active diluent and the epoxy resin is 0.1-2:50-100:100.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. The five-membered cyclic carbonate group-grafted modified graphene oxide prepared by the present invention has excellent compatibility with non-isocyanate polyurethane matrices and can be evenly dispersed within the matrix. Because the five-membered cyclic carbonate group-grafted modified graphene oxide dispersed in the cyclic carbonate reactive diluent has similar polarity, the former can be evenly dispersed in the solution. When this solution reacts with amines and epoxy resins in subsequent steps, the graphene can also be evenly dispersed in the system.

[0030] 2. The five-membered cyclic carbonate group-grafted modified graphene oxide prepared by the present invention exhibits both strong physical and chemical bonding with the non-isocyanate polyurethane matrix. The composite material exhibits significantly improved tensile and tear strength compared to the unmodified material, along with excellent toughness, mechanical properties, and load transfer capacity. This is because both the five-membered cyclic carbonate groups on the graphene oxide surface and the cyclic carbonate groups in the diluent can undergo a ring-opening reaction with amines to form -NHCOO- groups containing a -OH group at the β-position. These groups can form numerous internal hydrogen bonds (physical bonding) within the molecular chain system, thereby enhancing mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is the infrared spectrum of modified graphene oxide at different preparation stages in Example 1;

[0032] Among them, (1) is the infrared spectrum of original graphene oxide; (2) is the infrared spectrum of graphene oxide modified by isocyanate group grafting; (3) is the infrared spectrum of graphene oxide modified by five-membered cyclic carbonate group grafting.

[0033] Figure 2 is the SEM image of the tensile cross section of the composite material;

[0034] Among them, (1) is the tensile cross-section SEM image of the original graphene oxide / non-isocyanate polyurethane composite material; (2) is the tensile cross-section SEM image of the modified graphene oxide / non-isocyanate polyurethane composite material. DETAILED DESCRIPTION

[0035] The features and advantages of the present invention will be further described below with reference to the embodiments. However, the embodiments should be understood as merely illustrating the technical solutions of the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0036] Example 1: Preparation of five-membered cyclic carbonate group-grafted modified graphene oxide

[0037] 1) Add 100 ml of N, N-dimethylformamide (DMF) to a reactor, add 100 mg of graphene oxide, and disperse in a water bath ultrasonically for 2 hours. Then add 5 g of diphenylmethane diisocyanate (MDI) and disperse in a water bath ultrasonically under the protection of N2 for 2 hours. Then, raise the water bath temperature to 50°C and continue the reaction for 10 hours to obtain an MDI-grafted graphene oxide solution. The graphene oxide solution is washed three times with DMF and then five times with CH2Cl2 to obtain an isocyanate-grafted graphene oxide intermediate.

[0038] 2) Add 100 ml of DMF to the reactor, add 100 mg of the modified graphene oxide intermediate thereto, and perform water bath ultrasonic dispersion under the protection of N2 for 2 hours; then add 400 mg of glycerol carbonate and continue ultrasonic dispersion for 1 hour; then raise the temperature to 70°C and continue the reaction for 24 hours to obtain a graphene oxide solution grafted with pentacyclic carbonate groups; wash the graphene oxide solution five times with DMF and then five times with CH2Cl2, and then place it in a freeze dryer for drying to obtain graphene oxide grafted with pentacyclic carbonate groups.

[0039] The modified graphene oxide in each preparation stage in Example 1 was characterized by infrared spectroscopy, and the results were as follows: Figure 1As shown. Among them, (1) is the infrared spectrum of the original graphene oxide in step 1), (2) is the infrared spectrum of the graphene oxide intermediate modified by isocyanate group grafting obtained in step 1), and (3) is the infrared spectrum of the graphene oxide modified by five-membered cyclic carbonate group grafting obtained in step 2). In the figure, 3500cm -1 ~3200cm -1 is the stretching vibration peak of hydroxyl group on the graphene oxide surface; 1640 cm -1 is the carbon-carbon double bond skeleton vibration of the benzene ring. In (2), the graphene oxide modified by isocyanate group grafting has a wavelength of 2270 cm -1 There is an absorption peak of isocyanate group at 2270 cm -1 The absorption peak of the isocyanate group disappears completely at 1780 cm -1 The C=O absorption peak of cyclic carbonate appears at , indicating that the cyclic carbonate group is successfully grafted onto the graphene oxide surface.

[0040] The following Examples 1-1, 1-2, and 1-3 are based on Example 1, except that DMF in steps 1) and 2) is replaced with other solvents. All other conditions remain the same as in Example 1, and graphene oxide grafted with five-membered cyclic carbonate groups is prepared using the same method as in Example 1. The solvents used in each example are listed in Table 1 below. The objective was to investigate whether replacing DMF with other solvents, as well as using different solvents in steps 1) and 2), affects the mechanical properties of the resulting modified graphene oxide composites.

[0041]

[0042] Example 2: Preparation of composite materials

[0043] 0.6 g of the five-membered cyclic carbonate group-grafted modified graphene oxide prepared in Example 1 was added to 100 g of polypropylene glycol diglycidyl ether type cyclic carbonate (number average molecular weight of 1200 g / mol), and ultrasonically dispersed in a water bath for 3 h; then 17.2 g of triethylenetetramine was added to the mixed system and reacted at 90° C. for 4 h; then 100 g of bisphenol A type epoxy resin E51 was added to the prepolymer, stirred and mixed uniformly, poured into a mold and cured at 100° C. for 1 h to obtain the modified graphene oxide / non-isocyanate polyurethane composite material. The tensile cross-section SEM image of the modified graphene oxide / non-isocyanate polyurethane composite material is shown in FIG. Figure 2 As shown in (2).

[0044] In the following Examples 2-(1-1), 2-(1-2), and 2-(1-3), modified graphene oxide prepared in Examples 1-1, 1-2, and 1-3, respectively, were used to prepare modified graphene oxide / non-isocyanate polyurethane composites using the same method as in Example 2. The mechanical properties of the composites are shown in Table 2 below.

[0045]

[0046] Toughness / MJ / m 3 Test: Refer to the literature Polymer, 2007, 48(7):1857-1865.; Tear strength / KN / m test: Refer to GB / T 529-1999; Tensile strength / Mpa test: Refer to GB / T 528-1998, the test tensile rate is 500mm / min.

[0047] The mechanical properties test results in Table 2 show that the mechanical properties of the composite materials of Examples 2-(1-1), 2-(1-2), and 2-(1-3) differ somewhat from those of Example 2. This is because graphene oxide disperses differently in different organic solvents due to differences in the solubility parameters between the surface functional groups and the solvent. The dispersibility of graphene oxide directly affects its subsequent reactions with organic groups. In both steps 1) and 2) of Example 1, DMF was used. The good affinity between graphene oxide and the oxygen-containing groups in DMF facilitates dispersion. Furthermore, ultrasound can exfoliate the graphene oxide flakes to a certain extent. While graphene oxide can also disperse evenly in dimethyl sulfoxide and N,N-dimethylacetamide, the differences in solubility parameters and the higher boiling points of these solvents significantly affect the actual reaction of the graphene oxide during subsequent processing. In addition, acetone and THF also have good dispersibility for graphene oxide, but both have low boiling points and vapor pressures. During the ultrasonic dispersion process, they are easily vaporized and their wettability for graphene oxide is slightly worse than that of DMF. Therefore, the mechanical properties of the corresponding Example 2-(1-3) are slightly lower than those of Example 2.

[0048] The following Examples 2(1)-1, 2(2)-1, and 2(3)-1 are based on Example 2, except that the modified graphene oxide prepared in Example 2 is used to prepare modified graphene oxide / non-isocyanate polyurethane composites. The cyclic carbonate reactive diluent, polyamine, and epoxy resin used in each example are listed in Table 3 below. Other conditions are the same as in Example 2. The purpose is to investigate whether the use of different cyclic carbonate reactive diluents, polyamines, and epoxy resins to prepare the composites affects their mechanical properties. The mechanical properties of the composites are shown in Table 4 below.

[0049]

[0050]

[0051] Toughness / MJ / m 3 Test: Refer to the literature Polymer, 2007, 48(7):1857-1865.; Tear strength / KN / m test: Refer to GB / T 529-1999; Tensile strength / Mpa test: Refer to GB / T 528-1998, the test tensile rate is 500mm / min.

[0052] From the mechanical property test results in Table 4, it can be seen that the mechanical properties of the composite materials of Example 2 (1)-1, Example 2 (2)-1, and Example 2 (3)-1 have significant performance differences compared with those of Example 2, which is mainly due to the differences in the types of cyclic carbonate active diluent, polyamine and epoxy resin. Compared with Example 2, the type of cyclic carbonate selected in Example 2 (1)-2 is polypropylene glycol diglycidyl ether type cyclic carbonate with a molecular weight of 2500 g / mol, and the type of polyamine is D230. Therefore, the composite material prepared in Example 2 (1)-2 contains longer-chain flexible alkane chains, which can give the corresponding product better flexibility. Therefore, the tensile strength and tear strength of the corresponding product are reduced, while the elongation at break and toughness are significantly improved, which can reach 242.7% and 26.5 MJ / m respectively. 3 .

[0053] As for Example 2 (2) -1, the cyclic carbonate types selected are propylene carbonate and hexanediol diglycidyl ether type cyclic carbonate. Compared with the polypropylene glycol diglycidyl ether type cyclic carbonate in Example 2, the molecular chain is shorter. At the same time, the polyamine types selected are difunctional 1,3-propylenediamine and 1,6-hexanediamine. Therefore, the prepared composite material has shorter chain segments and the number of cross-linking points between the molecular chains is more moderate, so its tensile strength and tear strength can reach 29.7MPa and 94.5KN / m respectively. In addition, although the elongation at break of the composite material is reduced to 86.4%, the toughness can be as high as 22.7 MJ / m 3 The modified graphene oxide / non-isocyanate polyurethane composite material prepared by this method can achieve both mechanical strength and high flexibility.

[0054] For Example 2 (3)-1, the cyclic carbonate diluent used was 1,4-butanediol diglycidyl ether type cyclic carbonate, the polyamine used was tetraethylene pentamine, and the epoxy resin used was a multifunctional phenolic epoxy resin F44. Compared with Example 2, the flexible alkane chain in the cyclic carbonate diluent was shortened, and the number of secondary amines in the polyamine structure increased. At the same time, the epoxy resin also provided multifunctional reactive groups. Therefore, the tensile strength of the corresponding composite material was greatly improved, but the flexibility was greatly reduced, with the elongation at break and toughness being only 69.5% and 12.7 MJ / m, respectively. 3 In addition, the tear strength is also reduced accordingly.

[0055] Therefore, through the analysis of the above examples, it is possible to select the types of cyclic carbonate diluent, polyamine and epoxy resin, and preferably select the ratio required for actual use, so as to obtain a composite material with suitable performance.

[0056] Example 3: Preparation of five-membered cyclic carbonate group-grafted modified graphene oxide

[0057] 1) Add 50 ml of N, N-dimethylacetamide to a reactor, add 100 mg of graphene oxide, and disperse in a water bath by ultrasonication for 3 hours. Then, add 2 g of MDI and disperse in a water bath by ultrasonication under the protection of N2 for 3 hours. Then, raise the water bath temperature to 60°C and continue the reaction for 10 hours to obtain an MDI-grafted graphene oxide solution. The graphene oxide solution is washed four times with DMF and then six times with CH2Cl2 to obtain an isocyanate-grafted graphene oxide intermediate.

[0058] 2) Add 50 ml of N, N-dimethylacetamide to the reactor, add 100 mg of the modified graphene oxide intermediate thereto, and perform water bath ultrasonic dispersion under the protection of N2 for 3 hours; then add 150 mg of glycerol carbonate and continue ultrasonic dispersion for 0.5 hours; then raise the temperature to 60°C and continue the reaction for 24 hours to obtain a graphene oxide solution grafted with pentacyclic carbonate groups; wash the graphene oxide solution three times with DMF and then six times with CH2Cl2, and then place it in a freeze dryer for drying to obtain graphene oxide grafted with pentacyclic carbonate groups.

[0059] Example 4: Preparation of composite materials

[0060] 0.1 g of the five-membered cyclic carbonate group-grafted modified graphene oxide obtained in Example 3 was added to 50 g of ethylene carbonate, and the mixture was ultrasonically dispersed in a water bath for 2 h. Subsequently, 16 g of ethylenediamine was added to the mixed system and reacted at 60° C. for 8 h. Then, 100 g of bisphenol A epoxy resin E44 was added to the prepolymer, stirred and mixed evenly, poured into a mold, and cured at 100° C. for 2 h.

[0061] Example 5: Preparation of five-membered cyclic carbonate group-grafted modified graphene oxide

[0062] 1) Add 150 ml of acetone to a reactor, add 100 mg of graphene oxide thereto, and disperse in a water bath ultrasonically for 3 hours; then add 10 g of MDI and disperse in a water bath ultrasonically under the protection of N2 for 4 hours; then raise the water bath temperature to 70°C and continue the reaction for 12 hours to obtain an MDI-grafted graphene oxide solution; wash the graphene oxide solution with DMF five times and then with CH2Cl2 eight times to obtain an isocyanate-grafted graphene oxide intermediate;

[0063] 2) Add 200 ml of acetone to the reactor, add 100 mg of the modified graphene oxide intermediate thereto, and perform water bath ultrasonic dispersion under the protection of N2 for 4 hours; then add 300 mg of glycerol carbonate and continue ultrasonic dispersion for 1 hour; then raise the temperature to 70°C and continue the reaction for 24 hours to obtain a graphene oxide solution grafted with pentacyclic carbonate groups; wash the graphene oxide solution with DMF 5 times, then with CH2Cl2 8 times, and then place it in a freeze dryer for drying to obtain graphene oxide grafted with pentacyclic carbonate groups.

[0064] Example 6: Preparation of composite materials

[0065] 0.5 g of the modified graphene oxide having the structure shown in (II) obtained in Example 5 was added to 80 g of polyethylene glycol diglycidyl ether type cyclic carbonate (number average molecular weight of 1000 g / mol), and ultrasonically dispersed in a water bath for 4 h; then 14.5 g of diethylenetriamine was added to the mixed system and reacted at 100° C. for 2 h; then 100 g of bisphenol A epoxy resin E54 was added to the prepolymer, stirred and mixed evenly, poured into a mold, and cured at 100° C. for 1.5 h to obtain the product.

[0066] Example 7: Preparation of five-membered cyclic carbonate group-grafted modified graphene oxide

[0067] 1) Add 200 ml of tetrahydrofuran to a reactor, add 100 mg of graphene oxide thereto, and disperse in a water bath by ultrasonication for 3 hours; then add 5 g of MDI and disperse in a water bath by ultrasonication under the protection of N2 for 3 hours; then raise the water bath temperature to 50°C and continue the reaction for 11 hours to obtain an MDI-grafted graphene oxide solution; wash the graphene oxide solution with DMF five times and then with CH2Cl2 five times to obtain an isocyanate-grafted graphene oxide intermediate;

[0068] 2) Add 150 ml of tetrahydrofuran to the reactor, add 100 mg of the modified graphene oxide intermediate thereto, and perform water bath ultrasonic dispersion for 3 hours under the protection of N2; then add 50 mg of glycerol carbonate and continue ultrasonic dispersion for 1 hour; then raise the temperature to 60°C and continue the reaction for 24 hours to obtain a graphene oxide solution grafted with pentacyclic carbonate groups; wash the graphene oxide solution with DMF three times, then with CH2Cl2 five times, and then place it in a freeze dryer for drying to obtain graphene oxide grafted with pentacyclic carbonate groups.

[0069] Example 8: Preparation of composite materials

[0070] 2 g of the five-membered cyclic carbonate group-grafted modified graphene oxide prepared in Example 7 was added to 120 g of ethylene glycol diglycidyl ether type cyclic carbonate, and ultrasonically dispersed in a water bath for 2 h; then 45 g of polyetheramine was added to the mixed system and reacted at 80° C. for 6 h; then 100 g of phenolic epoxy resin F-44 was added to the prepolymer, stirred and mixed evenly, poured into a mold, and cured at 100° C. for 2 h.

[0071] The present invention is further described in more detail with reference to the following comparative examples.

[0072] Comparative Example 1

[0073] This comparative example is similar to Example 2 except that modified graphene oxide is not added. Specifically, 17 g of triethylenetetramine was added to 100 g of polypropylene glycol diglycidyl ether-type cyclic carbonate (number average molecular weight 1200 g / mol) and reacted at 90°C for 4 hours. Then, 100 g of bisphenol A epoxy resin E51 was added, stirred and mixed thoroughly, and the mixture was poured into a mold and cured at 100°C for 1 hour to obtain a non-isocyanate polyurethane polymer.

[0074] Comparative Example 2

[0075] Compared with Example 2, this comparative example uses pristine graphene oxide instead of modified graphene oxide to prepare a hybrid non-isocyanate polyurethane composite material. Specifically, 0.6g of pristine graphene oxide was added to 100g of polypropylene glycol diglycidyl ether-type cyclic carbonate (number average molecular weight of 1200g / mol), and ultrasonically dispersed in a water bath for 3h. Triethylenetetramine was then added to the mixture and reacted at 90°C for 4h. 100g of bisphenol A epoxy resin E51 was then added, stirred and mixed uniformly, poured into a mold, and cured at 100°C for 1h to obtain the obtained composite material. The tensile cross-section SEM image of the pristine graphene oxide / non-isocyanate polyurethane composite is shown in FIG. Figure 2 As shown in (1).

[0076] Comparative Example 3

[0077] Compared to Example 2, this comparative example used graphene oxide grafted with isocyanate groups instead of graphene oxide grafted with five-membered cyclic carbonate groups to prepare a hybrid non-isocyanate polyurethane composite. Specifically, 0.6 g of graphene oxide grafted with isocyanate groups was added to 100 g of polypropylene glycol diglycidyl ether-type cyclic carbonate (number-average molecular weight 1200 g / mol). The mixture was ultrasonically dispersed in a waterbath for 3 hours. Triethylenetetramine was then added to the mixture, reacted at 90°C for 4 hours, and then 100 g of bisphenol A epoxy resin E51 was added. The mixture was stirred and mixed thoroughly, and the mixture was poured into a mold and cured at 100°C for 1 hour.

[0078] Mechanical properties test comparison test

[0079] The composite materials prepared in Examples 2, 4, 6, 8 and Comparative Examples 2-3, and the polymer prepared in Comparative Example 1 were molded into sheets, respectively, and then tested according to the following mechanical property test standards. The test results are shown in Table 5 below.

[0080] Toughness / MJ / m 3 Test: Refer to Polymer, 2007, 48(7):1857-1865.

[0081] Tear strength / KN / m test: refer to GB / T 529-1999;

[0082] Tensile strength / Mpa test: refer to GB / T 528-1998, the test tensile rate is 500mm / min.

[0083]

[0084] From the above examples 2, 4, 6, 8 and comparative examples 1-3, it can be seen that compared with the polymer without modified graphene oxide (comparative example 1), the composite material with the addition of original graphene oxide (comparative example 2) and the composite material with the addition of isocyanate group-grafted modified graphene oxide (comparative example 3), the mechanical properties of the composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide (examples 2, 4, 6, 8) of the present invention are significantly improved, with a tensile strength of 15.7 to 42.2 MPa, a tear strength of 43.1 to 87 KN / m, and a toughness of 7.24 to 16 MJ / m 3 The composite materials containing pristine graphene oxide and the composite materials containing isocyanate-grafted modified graphene oxide showed some improvement in tensile strength and tear strength, but their toughness decreased. However, the composite materials containing five-membered cyclic carbonate-grafted modified graphene oxide showed a significant improvement in toughness.

[0085] from Figure 2 The SEM images of the tensile cross-sections of the composite materials (1) and (2) also show that compared Figure 2 In (1), Figure 2 The graphene sheets in (2) are dispersed more uniformly and densely in the composite material of the five-membered cyclic carbonate group-grafted modified graphene oxide. Therefore, the five-membered cyclic carbonate group-grafted modified graphene oxide / non-isocyanate polyurethane composite material prepared by the modification method of the present invention has excellent mechanical properties.

[0086] The above embodiments are only for better illustrating the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent replacements, improvements, etc. based on the above contents of the present invention fall within the scope of protection of the present invention.

Claims

1. A method for preparing a non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide, characterized in that: The following steps are involved: A. Add the five-membered cyclic carbonate group-grafted modified graphene oxide into a cyclic carbonate active diluent, and heat in a water bath and ultrasonically disperse for 2 to 4 hours; B. adding a polyamine to the solution of step A, reacting at 60-100° C. for 2-8 hours to obtain a prepolymer containing modified graphene oxide; C. adding epoxy resin to the prepolymer of step B and mixing them evenly, and curing them at 100° C. for 1 to 2 hours to finally obtain a non-isocyanate polyurethane composite material containing modified graphene oxide; The five-membered cyclic carbonate group grafted modified graphene oxide is prepared by the following method: 1) Preparation of isocyanate-grafted graphene oxide: adding an organic solvent to a reactor, adding graphene oxide thereto, and ultrasonically dispersing the mixture in a water bath at room temperature for 2-4 hours; then adding diphenylmethane diisocyanate, and ultrasonically dispersing the mixture in a water bath under inert gas protection for 2-5 hours; then heating the water bath to 50-70°C, and continuing the reaction for 10-12 hours to obtain an isocyanate-grafted graphene oxide solution; and washing the product solution to obtain an isocyanate-grafted graphene oxide intermediate. 2) Preparation of graphene oxide grafted with pentacyclic carbonate groups: an organic solvent is added to a reactor, the modified graphene oxide intermediate prepared in step 1) is added thereto, and ultrasonic dispersion is carried out in a water bath under inert gas protection for 2 to 4 hours; glycerol carbonate is then added, and ultrasonic dispersion is continued for 0.5 to 1 hour; the temperature is then raised to 50 to 70° C., and the reaction is continued for 24 hours to obtain a graphene oxide solution grafted with pentacyclic carbonate groups; the product solution is washed and dried to obtain graphene oxide grafted with pentacyclic carbonate groups.

2. The method for preparing a non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step A, the cyclic carbonate reactive diluent is one or more of ethylene carbonate, propylene carbonate, ethylene glycol diglycidyl ether type cyclic carbonate, 1,4-butanediol diglycidyl ether type cyclic carbonate, hexanediol diglycidyl ether type cyclic carbonate, polyethylene glycol diglycidyl ether type cyclic carbonate, and polypropylene glycol diglycidyl ether type cyclic carbonate; the number average molecular weight of the polyethylene glycol diglycidyl ether type cyclic carbonate is 600 to 2000 g / mol; the number average molecular weight of the polypropylene glycol diglycidyl ether type cyclic carbonate is 500 to 2500 g / mol.

3. The method for preparing the non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step B, the polyamine is one or more of ethylenediamine, 1,3-propylenediamine, 1,6-hexanediamine, polyetheramine D230, polyetheramine T403, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

4. The method for preparing a non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step C, the epoxy resin is one or more of bisphenol A epoxy resin E51, E44, E54, bisphenol F epoxy resin NPEF170 or novolac epoxy resin F-44.

5. The method for preparing the non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: The mass ratio of the modified graphene oxide, the cyclic carbonate active diluent and the epoxy resin is 0.1-2:50-100:

100.

6. The method for preparing a non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step 1) or step 2) of preparing modified graphene oxide, the inert gas is nitrogen; and the organic solvent is selected from any one of N, N-dimethylformamide, N, N-dimethylacetamide, acetone, tetrahydrofuran, and dimethyl sulfoxide.

7. The method for preparing a non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step 1) of preparing the modified graphene oxide, the mass ratio of the graphene oxide to the organic solvent is 1:150-500; the mass ratio of the graphene oxide to the diisocyanate is 1:20-100.

8. The method for preparing the non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step 2) of preparing the modified graphene oxide, the mass ratio of the modified graphene oxide intermediate to the organic solvent is 1:500-2000; the mass ratio of the modified graphene oxide intermediate to glycerol carbonate is 1:0.5-4.

9. The method for preparing a non-isocyanate polyurethane composite material containing five-membered cyclic carbonate group-grafted modified graphene oxide according to claim 1, characterized in that: In step 1) or step 2) of preparing modified graphene oxide, the washing method is: first centrifuging the product, washing it with N, N-dimethylformamide for 3 to 5 times, and then washing it with dichloromethane for 5 to 8 times.

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