Preparation method of graphene oxide modified phthalonitrile resin

Abstract

The invention relates to a preparation method of graphene oxide modified phthalonitrile resin, and belongs to the technical field of toughening and reinforcing of high-temperature-resistant resin. The preparation method of the graphene oxide modified phthalonitrile resin comprises the following steps: carrying out cyanation modification on the surface of graphene oxide by adopting aminated phthalonitrile; carrying out mechanical blending dispersion on the modified graphene and the phthalonitrile resin; and finally, heating and curing the resin to obtain a modified phthalonitrile resin cured product, or preparing a fiber-reinforced phthalonitrile resin-based composite material. According to the preparation method, cyanation modification is carried out on the graphene oxide, so that the compatibility of the graphene oxide and the phthalonitrile resin is improved, the dispersion effect and the toughening and reinforcing effect of the graphene oxide in the phthalonitrile resin are improved, and the mechanical property of the fiber-reinforced phthalonitrile resin-based composite material can also be improved.

Description

Technical Field

[0001] The invention relates to a graphene oxide modified phthalonitrile resin and a preparation method thereof, and belongs to the technical field of toughening and strengthening of high-temperature resistant resins. Background Art

[0002] Phthalonitrile is a high-temperature resistant thermosetting resin system. It utilizes the carbon-nitrogen triple bond (—C≡N) at the ortho position of the benzene ring as a reactive cyano group. During crosslinking and curing, the ortho-cyano group absorbs electrons, forming conjugated stabilizing aromatic heterocycles such as phthalocyanine and triazine rings through addition reactions. Its glass transition temperature is greater than 450°C. Phthalonitrile resins have attracted widespread attention in aerospace and other fields due to their advantages, such as the absence of small molecule release during curing and high thermal stability. They are used in high-temperature load-bearing and heat-resistant structures. Their heat resistance is higher than that of bismaleimide and benzoxazine resins, their processability is superior to that of polyimide resins, and their cost is reasonable. They hold great promise for application in advanced composite materials. However, the high crosslink density and strong molecular chain rigidity of phthallonitrile resins result in poor toughness and low mechanical properties of the resin and composites, which has severely hindered their further development and application. Adopt traditional thermosetting resin toughening mode, as grafting flexible chain segment at molecular chain, blending with thermoplastic resin, can significantly reduce the heat resistance of phthalonitrile resin.Graphene oxide (GO) is due to its own excellent heat resistance, mechanical property and surface activity, thereby improves resin toughness and intensity by absorbing energy such as interface action, bridging action in resin matrix, and does not reduce the heat resistance of resin.But along with the increase of graphene oxide content, owing to reunion, cause toughening and strengthening effect to obviously reduce, performance fluctuation is large.In addition, there is no group that obvious chemical bonding can occur between graphene oxide and phthalonitrile resin, and both compatibility is relatively poor, further reduces the dispersibility of graphene oxide in resin and the toughening and strengthening effect after resin curing.Therefore, how to promote the compatibility of graphene oxide and phthalonitrile resin becomes the key of phthalonitrile resin modification. This patent achieves high-yield, low-cost preparation of cyanated graphene through a simple and efficient preparation method, improves the compatibility of graphene with phthalonitrile resin, and can significantly improve the mechanical properties and heat resistance of phthalonitrile resin and its fiber-reinforced composites. Summary of the Invention

[0003] The purpose of the present invention is to provide a simple and efficient method for cyanation modification of graphene oxide, improve the compatibility with phthalonitrile resin, and enhance the dispersion effect and toughening and strengthening effect of graphene oxide in phthalonitrile resin.

[0004] 1. The present invention provides a method for preparing a graphene oxide modified phthalonitrile resin, comprising the following steps:

[0005] (1) Graphene oxide (GO) is surface-chlorinated by thionyl chloride, and chlorinated graphene (GO-COCl) powder is obtained after drying the thionyl chloride;

[0006] (2) Surface amidation modification of acylated graphene oxide (GO-COCl) was performed using aminophthalonitrile (APN), followed by washing with N,N-dimethylformamide (DMF) and centrifugation to remove unreacted APN, followed by vacuum drying to obtain cyanated graphene (GO-APN) powder;

[0007] (3) mechanically blending the cyanated graphene (GO-APN) powder with phthalonitrile resin, including mechanical stirring and three-roll milling;

[0008] (4) The resin mixture obtained in (3) is heated and cured to obtain a cured product or to prepare a fiber-reinforced composite material.

[0009] Preferably, the concentration of graphene oxide in thionyl chloride in step (1) is 0.00125-0.002 g / ml, the reaction temperature is 70-75° C., and the reaction time is 24 h.

[0010] Preferably, in the step (2), the concentration of the graphene chloride GO-COCl powder in the DMF solution is 0.0005-0.001 g / ml, the mass ratio of the aminophthalonitrile APN to GO-COCl is 3:1-5:1, the reaction temperature is 80-100° C., and the reaction time is 8-10 h.

[0011] Preferably, in step (3), the amount of GO-APN powder added to the phthalonitrile resin is 0.1%wt-0.5wt%, and mechanical stirring and dispersion are performed at 140-150°C, a stirring rate of 1000-2000 r / min, and a stirring time of 0.5-1h. Subsequently, after the three-roll temperature is heated to the softening point of the resin, the resin mixture is subjected to three-roll grinding once with a roller gap of 20-10 μm, once with a roller gap of 10-5 μm, and once with a roller gap of 5-3 μm.

[0012] Preferably, the heating rate of the oven in step (4) is 1-10°C / min, and the product is naturally cooled to room temperature after curing at 200-380°C / 5h-20h.

[0013] Preferably, in step (4), fiber-reinforced phthalonitrile resin-based composite materials such as carbon fiber, quartz fiber, high silica fiber, glass fiber, basalt fiber, and aramid fiber can be prepared, and the preparation process can adopt one of the following processes: autoclave process, molding process, liquid molding process, and winding process.

[0014] The preparation method of the graphene oxide modified phthalonitrile resin provided by the present invention has the advantages of simple process, high yield, good compatibility between graphene oxide and phthalonitrile resin, and excellent heat resistance, toughness and strength of the resin. (1) The graphene oxide is surface modified with amino phthalonitrile (APN), and then washed with N,N-dimethylformamide (DMF) and centrifuged to remove unreacted APN. The unreacted APN is washed with N,N-dimethylformamide (DMF) and centrifuged to remove the unreacted APN. After vacuum drying, cyanated graphene GO-APN powder is obtained, which has the characteristics of high yield and low cost. (2) The cyanated graphene GO-APN powder is mechanically blended with the phthalonitrile resin and finally solidified into a resin casting body, which is easy to operate and has a simple process. (3) The present invention modifies the surface of graphene oxide by first grafting acyl chloride bonds onto the surface oxygen-containing active groups, and then further subjecting the acyl chloride bonds to an amidation reaction to prepare graphene GO-APN powder in which amide bonds are grafted onto phthalonitrile. The powder has cyano grafted groups on the surface, thereby improving the compatibility between the graphene oxide and the resin. The graphene oxide-modified phthalonitrile resin and its fiber-reinforced composite prepared by the present invention have excellent mechanical properties and high heat resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the basic reaction chemical formula of the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0017] Example 1

[0018] The preparation method of the graphene oxide modified phthalonitrile resin of this embodiment comprises the following steps:

[0019] (1) 1 part by weight of GO powder and 80 parts by volume of thionyl chloride were added to a three-necked flask, nitrogen was passed through, the temperature was raised to 70°C, magnetic stirring was carried out for 24 hours, and then the GO-COCl powder was obtained by drying at 100°C for 24 hours.

[0020] (2) 1 part by weight of the chlorinated GO-COCl powder obtained in (1) and 200 parts by volume of DMF solvent were added to a three-necked flask, and 3 parts by weight of aminophthalonitrile APN were added at 80°C. After reacting for 8 hours, the resulting solution was repeatedly added with DMF solvent, centrifuged several times, washed to a clear solution, and finally dried in a vacuum oven at 80°C for 24 hours to obtain GO-APN powder.

[0021] (3) 1 part by weight of the GO-APN powder obtained in (2) and 1000 parts by weight of 4,4-(phenoxy)phthalonitrile resin were mechanically stirred and dispersed at 150°C at a stirring rate of 1500 r / min for 1 h. After heating to the softening point of the resin, the resin mixture was subjected to three-roll milling once with a roller gap of 20-10 μm, once with a roller gap of 10-5 μm, and once with a roller gap of 5-3 μm.

[0022] (4) The phthalonitrile resin mixture obtained in (3) (denoted as 0.1% wt GO-APN) was heated and cured at 375°C for 5 h at a heating rate of 1°C / min and then naturally cooled to room temperature.

[0023] Example 2

[0024] The preparation method of the graphene oxide modified phthalonitrile resin of this embodiment comprises the following steps:

[0025] (1) 1 part by weight of GO powder and 80 parts by volume of thionyl chloride were added to a three-necked flask, nitrogen was passed through, the temperature was raised to 70°C, magnetic stirring was carried out for 24 hours, and then the GO-COCl powder was obtained by drying at 100°C for 24 hours.

[0026] (2) 1 part by weight of the chlorinated GO-COCl powder obtained in (1) and 200 parts by volume of DMF solvent were added to a three-necked flask, and 4 parts by weight of aminophthalonitrile APN were added at 80°C. After reacting for 8 hours, the resulting solution was repeatedly added with DMF solvent, centrifuged several times, washed to a clear solution, and finally dried in vacuum at 80°C for 24 hours to obtain GO-APN powder.

[0027] (3) 1 part by weight of the GO-APN powder obtained in (2) and 333 parts by weight of 4,4-(phenoxy)phthalonitrile resin were mechanically stirred and dispersed at 150°C at a stirring rate of 1500 r / min for 1 h. After heating to the softening point of the resin, the resin mixture was subjected to three-roll milling once with a roller gap of 20-10 μm, once with a roller gap of 10-5 μm, and once with a roller gap of 5-3 μm.

[0028] (4) The phthalonitrile resin mixture obtained in (3) (denoted as 0.3% wt GO-APN) was heated and cured at 375°C for 5 h at a heating rate of 1°C / min and then naturally cooled to room temperature.

[0029] Example 3

[0030] The preparation method of the graphene oxide functionalized modified phthalonitrile resin of this embodiment comprises the following steps:

[0031] (1) 1 part by weight of GO powder and 80 parts by volume of thionyl chloride were added to a three-necked flask, nitrogen was passed through, the temperature was raised to 70°C, magnetic stirring was carried out for 24 hours, and then the GO-COCl powder was obtained by drying at 100°C for 24 hours.

[0032] (2) 1 part by weight of the chlorinated GO-COCl powder obtained in (1) and 200 parts by volume of DMF solvent were added to a three-necked flask, and 4 parts by weight of aminophthalonitrile APN were added at 80°C. After reacting for 8 hours, the resulting solution was repeatedly added with DMF solvent, centrifuged several times, washed to a clear solution, and finally dried in vacuum at 80°C for 24 hours to obtain GO-APN powder.

[0033] (3) 1 part by weight of the GO-APN powder obtained in (2) and 333 parts by weight of 4,4-(phenoxy)phthalonitrile resin were mechanically stirred and dispersed at 150°C at a stirring rate of 1500 r / min for 1 h. After heating to the softening point of the resin, the resin mixture was subjected to three-roll milling once with a roller gap of 20-10 μm, once with a roller gap of 10-5 μm, and once with a roller gap of 5-3 μm.

[0034] (4) The phthalonitrile resin mixture obtained in (3) (denoted as 0.3% wt GO-APN) was mixed with T700 grade carbon fiber to prepare a prepreg, and the composite material was prepared by a molding process and cured at 200°C / 4h, 315 / 5h, and 375°C / 5h.

[0035] Comparative Example 1

[0036] The preparation method of the graphene oxide modified phthalonitrile resin of this comparative example comprises the following steps:

[0037] A mixture of 1 part by weight of unmodified graphene oxide (GO) and 1000 parts by weight of 4,4-(phenoxy)phthalonitrile resin was poured into a mold and mechanically dispersed at 150°C at a stirring rate of 1500 rpm for 1 hour. After heating to the resin's softening point on three rollers, the resin mixture (denoted as 0.1% wt GO) was milled once with a roller gap of 20-10 μm, once with a roller gap of 10-5 μm, and once with a roller gap of 5-3 μm. After vacuum degassing, the mixture was cured at 375°C for 5 hours and then naturally cooled to room temperature.

[0038] Comparative Example 2

[0039] The preparation method of the graphene oxide modified phthalonitrile resin of this comparative example comprises the following steps:

[0040] A mixture of 1 part by weight of unmodified graphene oxide (GO) and 333 parts by weight of 4,4-(phenoxy)phthalonitrile resin was poured into a mold and mechanically dispersed at 150°C at a stirring rate of 1500 rpm for 1 hour. After heating to the resin's softening point on three rollers, the resin mixture (denoted as 0.3% wt GO) was milled once with a roller gap of 20-10 μm, once with a roller gap of 10-5 μm, and once with a roller gap of 5-3 μm. After vacuum degassing, the mixture was cured at 375°C for 5 hours at a heating rate of 5°C / min and then naturally cooled to room temperature.

[0041] Comparative Example 3

[0042] The preparation method of the graphene oxide modified phthalonitrile resin of this comparative example comprises the following steps:

[0043] Prepregs were prepared by combining 4,4-(phenoxy)phthalonitrile resin and T700 grade carbon fiber. Composite materials were prepared by a molding process and cured at 200℃ / 4h, 315℃ / 5h, and 375℃ / 5h.

[0044] Experimental example

[0045] Test Example 1, Example 2, Comparative Example 1, and Comparative Example 2, and the 5% thermal weight loss temperature, room temperature bending performance, and 400°C bending performance of the obtained graphene oxide and cyanated graphene GO-APN modified 4,4-(phenoxy)phthalonitrile resin in air atmosphere are shown in Tables 1, 2, and 3.

[0046] Table 1 T of phthalonitrile resin in air atmosphere 5％ Thermal weight loss temperature comparison

[0047]

[0048] Table 2 Bending properties of unmodified GO and GO-APN modified phthalonitrile resin at room temperature

[0049]

[0050] Table 3 400℃ flexural properties of unmodified GO and GO-APN modified phthalonitrile resin

[0051]

[0052]

[0053] Compared with the 5% thermal decomposition temperature, room temperature bending performance and 400°C bending performance of Comparative Example 1 and Comparative Example 2, the 5% thermal decomposition temperature of the resin modified with cyanated graphene GO-APN in Example 1 and Example 2 does not change much, that is, the heat stability remains unchanged, while the bending modulus and bending strength are improved. At the same time, the heat stability and mechanical properties of the resin modified with non-cyanated graphene GO are reduced compared with the graphene-free resin, indicating the necessity of cyanation modification of graphene oxide. The surface is grafted with cyano groups, which improves the dispersibility of graphene oxide and its compatibility with the resin, and improves the mechanical properties of the resin without reducing the temperature resistance of the phthalonitrile resin.

[0054] The mechanical properties of the T700-grade carbon fiber composite material prepared in Example 3 and Comparative Example 3 at room temperature and 450°C are shown in Table 4.

[0055] Table 4 Comparison of mechanical properties of T700 grade carbon fiber composite materials

[0056]

[0057] Compared with Comparative Example 3, the flexural strength, flexural modulus, and interlaminar shear strength of the carbon fiber composite material modified with cyanated graphene oxide in Example 3 are all improved, especially the retention rate of mechanical properties at high temperature is improved, which reflects the significant effect of cyanated graphene oxide modification.

[0058] As can be seen from the above examples, the present invention provides a cyanation modification of graphene oxide, which improves the compatibility of graphene oxide with phthalonitrile resin, improves the dispersion effect and high-temperature toughening and strengthening effect of graphene oxide in phthalonitrile resin, and improves the room temperature and high-temperature mechanical properties of phthalonitrile resin-based composite materials.

Claims

1. A method for preparing a graphene oxide modified phthalonitrile resin, characterized in that: The following steps are involved: (1) Graphene oxide (GO) is surface-chlorinated by thionyl chloride, and chlorinated graphene GO-COCl powder is obtained after drying the thionyl chloride; (2) Surface amidation modification of acylated graphene GO-COCl powder was performed using aminophthalonitrile (APN), followed by washing with N,N-dimethylformamide (DMF) and centrifugation to remove unreacted APN, followed by vacuum drying to obtain cyanated graphene (GO-APN) powder; (3) mechanically blending the cyanated graphene (GO-APN) powder with phthalonitrile resin, including mechanical stirring and three-roll milling; (4) The resin mixture obtained in (3) is heated and cured to obtain a cured product or to prepare a fiber-reinforced composite material.

2. The method for preparing graphene oxide-modified phthalonitrile resin according to claim 1, wherein: The method for chlorinating graphene oxide (GO) in step (1) comprises the following steps: first dispersing graphene oxide in thionyl chloride at a concentration of 0.00125-0.002 g / ml, heating to 70-75° C. for reaction for 24 hours, and drying at 80-100° C. for 24 hours to remove residual thionyl chloride to obtain chlorinated graphene GO-COCl powder.

3. The method for preparing graphene oxide-modified phthalonitrile resin according to claim 1, wherein: The method for amidating the chlorinated graphene GO-COCl in step (2) comprises the following steps: adding the chlorinated graphene GO-COCl into a DMF solvent at a concentration of 0.0005-0.001 g / ml, adding the chlorinated graphene GO-COCl into the DMF solution with a mass ratio of amination phthalonitrile APN to GO-COCl of 3:1-5:1, heating the amination phthalonitrile APN to the DMF solution to 80-100° C. and reacting for 8-10 hours. The obtained solution is repeatedly added with DMF solvent, centrifuged several times, washed to a clear solution, and finally vacuum dried at 70-80° C. for 24 hours to obtain cyanated graphene GO-APN powder.

4. The method for preparing graphene oxide-modified phthalonitrile resin according to claim 1, wherein: In the step (3), the amount of cyanide graphene GO-APN powder added to the phthalonitrile resin is 0.1-0.5 wt%; mechanical stirring and dispersion are performed at 140-150° C., the stirring rate is 1000-2000 r / min, and the stirring time is 0.5-1 h; Subsequently, after the temperature of the three rollers is heated to the softening point of the resin, the mechanically stirred resin mixture is ground once with a roller gap of 10-20 μm, once with a roller gap of 5-10 μm, and once with a roller gap of 3-5 μm.

5. The method for preparing graphene oxide-modified phthalonitrile resin according to claim 1, wherein: In the step (4), the heating rate of the oven is 1-10°C / min, and the mixture is naturally cooled to room temperature after being cured at 200-380°C / 5-20h.

6. The method for preparing graphene oxide-modified phthalonitrile resin according to claim 1, wherein: In the step (4), fiber-reinforced phthalonitrile resin-based composite materials such as carbon fiber, quartz fiber, high silica fiber, glass fiber, basalt fiber, and aramid fiber can be prepared, and the preparation process can adopt one of the following processes: autoclave process, molding process, liquid molding process, and winding process.

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