Silane coupling agent functionalized graphene oxide modified bismaleimide resin and preparation method thereof

Abstract

The invention provides silane coupling agent functionalized graphene oxide modified bismaleimide resin and a preparation method thereof, and belongs to the technical field of resin materials. The preparation method comprises the following steps: carrying out first modification treatment on graphene oxide, a silane coupling agent, a first organic solvent and water, carrying out second modification treatment on the obtained silane coupling agent modified graphene oxide, a second organic solvent and part of bismaleimide, mixing an obtained second modified product system with the rest of bismaleimide, and carrying out ball milling treatment; carrying out solvent replacement on the obtained ball-milled material liquid and a poor solvent of bismaleimide, mixing the obtained modified mixed powder with a cross-linking agent, and carrying out a cross-linking reaction to obtain a prepolymer; the prepolymer is subjected to curing treatment, and the silane coupling agent functionalized graphene oxide modified bismaleimide resin is obtained. The silane coupling agent functionalized graphene oxide modified bismaleimide resin prepared by the method provided by the invention has excellent mechanical properties and heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of resin materials, and particularly relates to a silane coupling agent-functionalized graphene oxide modified bismaleimide resin and a preparation method thereof. Background Art

[0002] The service temperature of bismaleimide resin is higher than that of traditional epoxy resins, and the processing difficulty is lower than that of polyimide resins. It is an extremely important thermosetting resin in the aerospace field. However, bismaleimide resin has a high crosslinking density, strong molecular chain rigidity, and poor toughness, which seriously hinders the further development and application of bismaleimide resin. Traditional toughening methods such as adding rubber containing active groups, chain extension with diamine, and forming an interpenetrating network structure usually reduce the crosslinking density of bismaleimide resin, resulting in an increase in toughness, but will have an adverse effect on the rigidity and heat resistance of bismaleimide resin, usually leading to a decrease in its glass transition temperature.

[0003] Due to its excellent mechanical properties, graphene oxide can be added to bismaleimide to hinder the movement of molecular chains at high temperatures, thereby increasing the glass transition temperature of bismaleimide resin. When bismaleimide resin is damaged, the crack deflects to improve its toughness, that is, it can simultaneously achieve the effects of toughening, strengthening, and improving heat resistance. However, graphene oxide is a nanomaterial with a small particle size and extremely high surface energy, which is easy to approach each other and agglomerate. Moreover, bismaleimide resin has a high viscosity and poor fluidity. These reasons lead to poor dispersion and serious agglomeration of graphene oxide in bismaleimide resin, and its function cannot be fully exerted. Summary of the Invention

[0004] The purpose of the present invention is to provide a silane coupling agent-functionalized graphene oxide modified bismaleimide resin and a preparation method thereof. The silane coupling agent-functionalized graphene oxide modified bismaleimide resin prepared by the method of the present invention has excellent mechanical properties and heat resistance.

[0005] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a silane coupling agent-functionalized graphene oxide modified bismaleimide resin, comprising the following steps:

[0007] Mix graphene oxide, a silane coupling agent, a first organic solvent and water, and perform a first modification treatment to obtain a silane coupling agent-modified graphene oxide;

[0008] Mix the silane coupling agent modified graphene oxide, the second organic solvent and a part of bismaleimide for a second modification treatment, and mix the obtained second modification product system with the remaining bismaleimide to obtain a premixed liquid; the second organic solvent is a good solvent for bismaleimide;

[0009] Perform ball milling on the premixed liquid to obtain a ball-milled liquid;

[0010] Mix the ball-milled liquid with a poor solvent of bismaleimide for solvent replacement to obtain a modified mixed powder;

[0011] Mix the modified mixed powder with a crosslinking agent for a crosslinking reaction to obtain a prepolymer;

[0012] Perform curing treatment on the prepolymer to obtain the silane coupling agent functionalized graphene oxide modified bismaleimide resin.

[0013] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane; the temperature of the first modification treatment is 50-80 °C and the time is 12-36 h.

[0014] Preferably, the second organic solvent includes N,N-dimethylformamide or N-methylpyrrolidone; the poor solvent of bismaleimide includes water or ethanol.

[0015] Preferably, the mixing of the silane coupling agent modified graphene oxide, the second organic solvent and a part of bismaleimide includes:

[0016] Perform a first mixing of the part of bismaleimide and a part of the second organic solvent to obtain a bismaleimide solution;

[0017] Perform a second mixing of the silane coupling agent modified graphene oxide and the remaining second organic solvent to obtain a silane coupling agent modified graphene oxide dispersion;

[0018] Perform a third mixing of the bismaleimide solution and the silane coupling agent modified graphene oxide dispersion.

[0019] Preferably, the mass of the part of bismaleimide is 10-30% of the total mass of bismaleimide; the mass ratio of the part of bismaleimide to the part of the second organic solvent is 10:8-50; the concentration of the silane coupling agent modified graphene oxide dispersion is 1-5 mg / mL; the mass ratio of the silane coupling agent modified graphene oxide dispersion to the total mass of bismaleimide is 0.1-20:110.

[0020] Preferably, the temperature of the second modification treatment is 30-60 °C and the time is 1-2 h.

[0021] Preferably, the ball milling process is performed at a rotation speed of 200 to 800 r / min and for a time of 2 to 8 hours.

[0022] Preferably, the cross-linking agent comprises diallyl bisphenol A, and the ratio of the mass of the cross-linking agent to the total mass of bismaleimide is 91-110:110; the temperature of the cross-linking reaction is 110-140° C., and the time is 1-2 hours.

[0023] The present invention provides a bismaleimide resin modified with graphene oxide functionalized by a silane coupling agent and prepared by the preparation method described in the above technical scheme.

[0024] The present invention provides application of the bismaleimide resin modified by graphene oxide functionalized by a silane coupling agent in the above technical solution in a structural composite material.

[0025] Beneficial effects: The present invention obtains silane coupling agent modified graphene oxide by grafting a silane coupling agent onto the surface of graphene oxide, which is beneficial to improving the bonding ability between graphene oxide and resin. In the present invention, part of the bismaleimide first reacts with the silane coupling agent modified graphene oxide and wraps on its surface to form a spherical shell structure, which is beneficial to reducing the agglomeration of graphene oxide sheets due to contact and avoiding agglomeration in subsequent treatment processes. The present invention adopts a ball-milling-assisted solution mixing method, so that the silane coupling agent modified graphene oxide and bismaleimide are mixed and ball-milled in a solution state. On the one hand, the drying process of the silane coupling agent modified graphene oxide can be reduced to maintain its dispersibility; on the other hand, the bismaleimide solution has good fluidity, and the silane coupling agent modified graphene oxide and bismaleimide can fully collide, contact, and react under the ball milling dispersion, which is beneficial to further improve the agglomeration. The present invention uses a low-boiling-point poor solvent (such as water) to precipitate the modified resin from its good solvent (i.e., the second organic solvent) by solvent replacement. The low-boiling-point poor solvent is easy to remove under the conditions of a relatively low heating temperature and a relatively short heating time, thereby solving the problem of the difficulty and incompleteness of removing the second organic solvent, and realizing convenient, rapid, efficient, and large-scale extraction of the bismaleimide resin. Therefore, the bismaleimide resin modified by the silane coupling agent functionalized graphene oxide prepared by the method of the present invention has excellent mechanical properties and heat resistance. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a bismaleimide resin functionalized with a silane coupling agent, comprising the following steps:

[0027] Mixing graphene oxide, a silane coupling agent, a first organic solvent and water, and performing a first modification treatment to obtain silane coupling agent-modified graphene oxide;

[0028] Mix the silane coupling agent modified graphene oxide, the second organic solvent and a part of bismaleimide, and conduct a second modification treatment. Mix the obtained second modification product system with the remaining bismaleimide to obtain a premixed liquid; the second organic solvent is a good solvent for bismaleimide;

[0029] Conduct ball milling treatment on the premixed liquid to obtain a ball milled liquid;

[0030] Mix the ball milled liquid with a poor solvent of bismaleimide to conduct solvent replacement to obtain a modified mixed powder;

[0031] Mix the modified mixed powder with a crosslinking agent to conduct a crosslinking reaction to obtain a prepolymer;

[0032] Conduct curing treatment on the prepolymer to obtain the silane coupling agent functionalized graphene oxide modified bismaleimide resin.

[0033] The modification of bismaleimide resin with graphene oxide is beneficial to improving its mechanical properties and heat resistance. However, graphene oxide has a small particle size, poor dispersibility in bismaleimide resin, and serious agglomeration, so its function cannot be fully exerted. Graphene oxide itself has a certain dispersibility in polar solvents, but after chemical modification, its dispersibility often decreases severely and it is prone to agglomeration. When using functionalized graphene oxide to modify bismaleimide resin, in order to maintain its good dispersion state, it is often necessary to perform freeze-drying or heat-drying and other treatments to obtain powder. This process is time-consuming, laborious, cumbersome, costly, and difficult for large-scale production. In addition, when using nanoparticles to modify resin, the nanoparticles need to be added to the resin, and usually the resin is required to be in a flowing state. The common methods are to heat and melt the resin or use the solution mixing method. For bismaleimide resin, the difference between its melting point and curing temperature is not too large, and the heated and melted resin is prone to premature gelation during the long-term stirring and mixing process. And the solution mixing method must finally remove the solvent after mixing evenly. Currently, the common method is to heat and evaporate the solvent. For bismaleimide resin, its good solvent can be N,N-dimethylformamide (DMF). This solvent has a high boiling point (153°C), the temperature for heating and evaporating is high, the time consumption is long, the heating temperature is close to the resin gel temperature, and it is also easy to cause premature gelation of the resin. Moreover, DMF is often not completely removed. Premature gelation and solvent residue will both cause a decrease in the performance of the final cured product (such as insufficient crosslinking degree or defects). In addition, currently, the mixing of nanoparticles into resin mostly adopts mechanical stirring or ultrasonic dispersion methods, and the dispersion effect is not very ideal. The present invention grafts a silane coupling agent onto the surface of graphene oxide, and at the same time adopts ball milling treatment and solvent replacement methods, which are beneficial to improving the dispersibility of graphene oxide in bismaleimide resin, and finally a bismaleimide resin modified with silane coupling agent-functionalized graphene oxide with excellent mechanical properties and heat resistance can be prepared. The method of the present invention will be described in detail below.

[0034] In the present invention, unless otherwise specified, the raw materials used are all commercially available products well-known to those skilled in the art or are prepared by methods well-known to those skilled in the art.

[0035] The present invention mixes graphene oxide, a silane coupling agent, a first organic solvent and water, and performs a first modification treatment to obtain a silane coupling agent-modified graphene oxide. As an embodiment of the present invention, the graphene oxide (GO) is used in the form of a GO dispersion liquid, and the concentration of the GO dispersion liquid can be 8-12 mg / mL, specifically 10 mg / mL, and the size of the GO can be 8-10 μm. In the examples of the present invention, the GO dispersion liquid is purchased from Hangzhou Gaoxi Technology Co., Ltd., and the model is GO1-DMF. As an embodiment of the present invention, the silane coupling agent can be γ-aminopropyltriethoxysilane; the first organic solvent can be an alcohol solvent, and the alcohol solvent can be ethanol, specifically anhydrous ethanol; the water can specifically be deionized water. As an embodiment of the present invention, the mass ratio of the silane coupling agent, the GO dispersion liquid, the first organic solvent and water can be 2:18-22:110-120:4-6, specifically 2:20:115:5. As an embodiment of the present invention, the temperature of the first modification treatment can be 50-80 °C, specifically 55 °C, 60 °C, 65 °C, 70 °C or 75 °C; the time can be 12-36 h, specifically 15 h, 20 h, 24 h or 30 h. As an embodiment of the present invention, after the first modification treatment, it may further include: washing and centrifuging the first modification product system obtained after the first modification treatment with N,N-dimethylformamide to remove the unreacted silane coupling agent, and collecting the solid material to obtain the silane coupling agent-modified graphene oxide.

[0036] After obtaining the silane coupling agent-modified graphene oxide, the present invention mixes the silane coupling agent-modified graphene oxide, a second organic solvent and a part of bismaleimide, and performs a second modification treatment to obtain a second modification product system. In the present invention, the second organic solvent is a good solvent for bismaleimide, and the second organic solvent may include N,N-dimethylformamide or N-methylpyrrolidone. As an embodiment of the present invention, the bismaleimide can be diphenyl bismaleimide, m-phenylene bismaleimide or phenyl bismaleimide.

[0037] As an embodiment of the present invention, the mixing of the silane coupling agent-modified graphene oxide, the second organic solvent and a part of bismaleimide may include: performing a first mixing of the part of bismaleimide and a part of the second organic solvent to obtain a bismaleimide solution; performing a second mixing of the silane coupling agent-modified graphene oxide and the remaining second organic solvent to obtain a silane coupling agent-modified graphene oxide dispersion liquid; and performing a third mixing of the bismaleimide solution and the silane coupling agent-modified graphene oxide dispersion liquid.

[0038] As an embodiment of the present invention, the mass of the partial bismaleimide can be 10-30% of the total mass of the bismaleimide, specifically 15%, 20%, 25% or 28%; the mass ratio of the partial bismaleimide to the partial second organic solvent can be 10:8-50, specifically 10:10, 10:15, 10:20 or 10:30; the first mixing can be carried out under ultrasonic conditions, the power of the ultrasonic can be 100-300W, specifically 150W, 200W, 250W or 300W; the time can be 10-60min, specifically 20min, 30min, 40min or 50min; the ultrasonic conditions are specifically based on the full dissolution of the partial bismaleimide. As an embodiment of the present invention, the concentration of the silane coupling agent modified graphene oxide dispersion can be 1-5mg / mL, specifically 2mg / mL, 3mg / mL or 4mg / mL; the present invention has no special limitation on the second mixing, and it is only necessary to fully disperse the silane coupling agent modified graphene oxide. As an embodiment of the present invention, the third mixing can be: adding the silane coupling agent modified graphene oxide dispersion to the bismaleimide solution under the condition of 30-60°C. As an embodiment of the present invention, the mass ratio of the silane coupling agent modified graphene oxide dispersion to the total mass of the bismaleimide can be 0.1-20:110, specifically 0.5:110, 1:110, 3:110, 5:110, 8:110, 10:110 or 15:110.

[0039] As an embodiment of the present invention, the temperature of the second modification treatment can be 30-60°C, specifically 35°C, 40°C, 45°C, 50°C or 55°C; the time can be 1-2h, specifically 1.5h; the second modification treatment can be carried out under stirring conditions, and the rotation speed of the stirring can be 1000-8000r / min, specifically 2000r / min, 4000r / min or 6000r / min. During the second modification treatment of the present invention, the surface of the silane coupling agent modified graphene oxide is provided with an amino (-NH2) functional group, which can undergo a Michael addition reaction with the double bond of the bismaleimide resin.

[0040] After the second modification treatment, the present invention does not need to carry out any post-treatment, and directly mixes the obtained second modification product system with the remaining bismaleimide to obtain a premixed liquid. As an embodiment of the present invention, the mixing can be carried out under stirring conditions; the rotation speed of the stirring can be 1000-8000r / min, specifically 2000r / min, 4000r / min or 6000r / min; the mixing time can be 1-2h, specifically 1.5h.

[0041] After obtaining the premixed liquid, the present invention subjects the premixed liquid to ball milling treatment to obtain a ball-milled liquid. As an embodiment of the present invention, the rotation speed of the ball milling treatment can be 200 - 800 r / min, specifically 300 r / min, 400 r / min, 500 r / min, 600 r / min or 700 r / min; the time can be 2 - 8 h, specifically 3 h, 4 h, 5 h, 6 h or 7 h. In the embodiments of the present invention, the ball milling treatment is specifically carried out in a ball mill.

[0042] After obtaining the ball-milled liquid, the present invention mixes the ball-milled liquid with a poor solvent of bismaleimide to carry out solvent replacement to obtain a modified mixed powder. As an embodiment of the present invention, the poor solvent of bismaleimide can include water or ethanol. The water can specifically be deionized water, and the ethanol can specifically be anhydrous ethanol; the mass ratio of the poor solvent of bismaleimide to the total mass of bismaleimide can be 200 - 800:110, specifically 300:110, 400:110, 500:110, 600:110 or 700:110. As an embodiment of the present invention, the solvent replacement can be carried out at room temperature (such as 25 °C). During the solvent replacement process of the present invention, solids precipitate out in the system. Subsequently, it is preferably to wash and filter the obtained solid-liquid mixed system with water 4 - 8 times, collect the solid material and dry it to obtain a modified mixed powder; the drying can be drying in an oven; the temperature of the drying in an oven can be 90 - 110 °C, specifically 100 °C; the drying time is based on ensuring sufficient drying.

[0043] After obtaining the modified mixed powder, the present invention mixes the modified mixed powder with a crosslinking agent to carry out a crosslinking reaction to obtain a prepolymer. As an embodiment of the present invention, the crosslinking agent includes diallylbisphenol A, and the mass ratio of the crosslinking agent to the total mass of bismaleimide can be 91 - 110:110, specifically 95:110, 100:110 or 105:110. As an embodiment of the present invention, the temperature of the crosslinking reaction can be 110 - 140 °C, specifically 120 or 130 °C; the time can be 1 - 2 h, specifically 1.5 h; the crosslinking reaction can be carried out under stirring conditions, and the rotation speed of the stirring can be 1000 - 3000 r / min, specifically 1500 r / min, 2000 r / min or 2500 r / min.

[0044] After obtaining the prepolymer, the present invention cures the prepolymer to obtain the silane coupling agent-functionalized graphene oxide modified bismaleimide resin. As an embodiment of the present invention, preferably, before the curing treatment, it may further include: subjecting the prepolymer to a defoaming treatment; the temperature of the defoaming treatment may be 120 to 160 °C, specifically 130 °C, 140 °C or 150 °C; the time of the defoaming treatment may be 30 to 60 min, specifically 40 min or 50 min; the defoaming treatment may be specifically carried out in a vacuum oven. As an embodiment of the present invention, the curing treatment may adopt stepwise curing, and the stepwise curing may be: keeping warm at 165 to 175 °C for 0.5 to 2 h, then keeping warm at 195 to 205 °C for 1 to 3 h, and finally keeping warm at 245 to 255 °C for 2 to 5 h; the stepwise curing may be specifically: keeping warm at 170 °C for 1 h, then keeping warm at 200 °C for 2 h, and finally keeping warm at 250 °C for 3 h.

[0045] The present invention provides the silane coupling agent-functionalized graphene oxide modified bismaleimide resin prepared by the preparation method described in the above technical solution. The silane coupling agent-functionalized graphene oxide modified bismaleimide resin of the present invention has excellent mechanical properties and heat resistance. The test example results show that the flexural strength of the silane coupling agent-functionalized graphene oxide modified bismaleimide resin provided by the present invention is 132 to 142 MPa, the flexural modulus may be 3.88 to 4.07 GPa, the glass transition temperature is 300 to 304 °C, and the 5% thermal decomposition temperature is 413 to 420 °C.

[0046] The present invention provides the application of the silane coupling agent-functionalized graphene oxide modified bismaleimide resin described in the above technical solution in structural composites. As an embodiment of the present invention, the structural composite material can be used in scenarios with certain requirements for temperature and mechanical properties in the aerospace field. The present invention has no special limitation on the specific application method, and the application method well-known to those skilled in the art can be adopted.

[0047] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0048] Example 1

[0049] (1) Add 20 mL of graphene oxide (GO) dispersion (the dispersant is DMF, the concentration is 10 mg / mL, and the size of GO is 8 - 10 μm; the GO dispersion is purchased from Hangzhou Gaoxi Technology Co., Ltd., model GO1-DMF), 115 mL of absolute ethanol, 5 mL of deionized water, and 2 g of KH550 into a three-necked flask, and react at 75 °C for 24 h; after the reaction, wash and centrifuge the obtained product system with N,N-dimethylformamide (DMF) to remove the unreacted KH550, and collect the solid material, which is the graphene oxide modified by silane coupling agent (KH550-GO). Mix the KH550-GO with DMF to obtain a KH550-GO dispersion with a concentration of 2 mg / mL;

[0050] (2) Add 30 parts by mass of diphenyl bismaleimide and 30 parts by mass of DMF into a flask, ultrasonicate for 30 min at a power of 300 W to completely dissolve the diphenyl bismaleimide, then add 5 parts by mass of the KH550-GO dispersion at 50 °C, and stir and react at a rotation speed of 2000 r / min for 1.5 h; after the reaction, add 80 parts by mass of diphenyl bismaleimide to the obtained product system, and stir and mix at a rotation speed of 2000 r / min for 1.5 h to obtain a premixed liquid;

[0051] (3) Pour the premixed liquid into the tank of a ball mill, and perform ball milling at a rotation speed of 500 r / min for 6 h to obtain a ball-milled liquid;

[0052] (4) At room temperature, pour the ball-milled liquid into 500 parts by mass of deionized water, and solids will precipitate. Wash and filter the obtained solid-liquid mixture system 4 times with deionized water, and collect the solid material and dry it at 100 °C to obtain a modified mixed powder;

[0053] (5) At 120 °C, mix the modified mixed powder with 100 parts by mass of diallyl bisphenol A, and stir and react at a rotation speed of 2000 r / min for 1.5 h to obtain a prepolymer;

[0054] (6) Perform degassing treatment on the prepolymer in a vacuum oven at 130 °C for 30 min, and then perform stepwise curing in the oven to obtain KH550-GO modified BMI resin; the stepwise curing is specifically as follows: keep warm at 170 °C for 1 h, then keep warm at 200 °C for 2 h, and finally keep warm at 250 °C for 3 h.

[0055] Example 2

[0056] Operate according to the method of Example 1, the difference is that the dosage of KH550-GO dispersion in this example is 12.5 parts by mass.

[0057] Example 3

[0058] The operation was carried out with reference to the method of Example 1, except that the dosage of KH550-GO dispersion liquid in this example was 20 parts by mass.

[0059] Comparative Example 1

[0060] No modification was carried out in this comparative example, and the specific steps were as follows:

[0061] (1) Add 100 parts by mass of diphenyl bismaleimide into a beaker, heat it to 120 °C, then add 100 parts by mass of diallyl bisphenol A, and stir and react for 1.5 h under the condition of a rotation speed of 2000 r / min to obtain a prepolymer;

[0062] (2) Carry out defoaming treatment on the prepolymer in a vacuum oven at 130 °C for 30 min, and then carry out stepwise curing in the oven to obtain an unmodified BMI resin; the specific stepwise curing process is as follows: keep the temperature at 170 °C for 1 h, then keep the temperature at 200 °C for 2 h, and finally keep the temperature at 250 °C for 3 h.

[0063] Comparative Example 2

[0064] KH550 was not used in this comparative example, and the specific steps were as follows:

[0065] (1) Add 30 parts by mass of diphenyl bismaleimide and 30 parts by mass of DMF into a flask, ultrasonically dissolve diphenyl bismaleimide completely under the condition of a power of 300 W for 30 min, then add 5 parts by mass of GO dispersion liquid with a concentration of 2 mg / mL at 50 °C, and stir and react for 1.5 h under the condition of a rotation speed of 2000 r / min; after the reaction, add 80 parts by mass of diphenyl bismaleimide to the obtained product system, and stir and mix for 1.5 h under the condition of a rotation speed of 2000 r / min to obtain a premixed liquid;

[0066] (2) Refer to the method of steps (3) to (6) in Example 1 for operation, and use the premixed liquid to prepare a GO-modified BMI resin.

[0067] Comparative Example 3

[0068] KH550 was not used, ball milling treatment was not carried out, and solvent replacement was not carried out in this comparative example, and the specific steps were as follows:

[0069] (1) Add 30 parts by mass of diphenyl bismaleimide and 30 parts by mass of DMF into a flask. Ultrasonicate for 30 min at a power of 300 W to completely dissolve diphenyl bismaleimide. Then add 5 parts by mass of a GO dispersion with a concentration of 2 mg / mL at 50 °C and stir and react for 1.5 h at a rotation speed of 2000 r / min. After the reaction, add 80 parts by mass of diphenyl bismaleimide to the obtained product system and stir and mix for 1.5 h at a rotation speed of 2000 r / min to obtain a premixed liquid;

[0070] (2) Dry the premixed liquid at 120 °C to obtain a modified mixed powder;

[0071] (3) Refer to the methods in steps (5) to (6) of Example 1 and use the modified mixed powder to prepare GO-modified BMI resin.

[0072] Comparative Example 4

[0073] In this comparative example, KH550 is not used and ball milling treatment is not carried out. The specific steps are as follows:

[0074] (1) Add 30 parts by mass of diphenyl bismaleimide and 30 parts by mass of DMF into a flask. Ultrasonicate for 30 min at a power of 300 W to completely dissolve diphenyl bismaleimide. Then add 5 parts by mass of a GO dispersion with a concentration of 2 mg / mL at 50 °C and stir and react for 1.5 h at a rotation speed of 2000 r / min. After the reaction, add 80 parts by mass of diphenyl bismaleimide to the obtained product system and stir and mix for 1.5 h at a rotation speed of 2000 r / min to obtain a premixed liquid;

[0075] (2) Pour the premixed liquid into 500 parts by mass of deionized water, and solids will precipitate. Wash and filter the obtained solid-liquid mixture system 4 times with deionized water, collect the solid material and dry it at 100 °C to obtain a modified mixed powder;

[0076] (3) Refer to the methods in steps (5) to (6) of Example 1 and use the modified mixed powder to prepare GO-modified BMI resin.

[0077] Comparative Example 5

[0078] In this comparative example, maleic anhydride-modified graphene oxide (MAH-GO) is used to replace silane coupling agent-modified graphene oxide. The specific steps are as follows:

[0079] (1) Add 30 mL of GO dispersion (the dispersant is DMF, with a concentration of 10 mg / mL, and the size of GO is 8 - 10 μm; the GO dispersion is purchased from Hangzhou Gaoxi Technology Co., Ltd., model GO1-DMF), 60 mL of DMF, and 10 g of maleic anhydride (MAH) into a three-necked flask, and react at 75 °C for 6 h; after the reaction, wash and centrifuge the obtained product system with DMF to remove the unreacted MAH, and collect the solid material, which is MAH-GO. Mix the MAH-GO with DMF to obtain a MAH-GO dispersion with a concentration of 2 mg / mL;

[0080] (2) Add 30 parts by mass of diphenyl bismaleimide and 30 parts by mass of DMF into a flask, ultrasonicate for 30 min at a power of 300 W to completely dissolve the diphenyl bismaleimide, then add 5 parts by mass of the MAH-GO dispersion at 50 °C, and stir and react at a rotation speed of 2000 r / min for 1.5 h; after the reaction, add 80 parts by mass of diphenyl bismaleimide to the obtained product system, and stir and mix at a rotation speed of 2000 r / min for 1.5 h to obtain a premixed liquid;

[0081] (3) Refer to the methods in steps (3) - (6) of Example 1 for operation, and use the premixed liquid to prepare MAH-GO modified BMI resin.

[0082] Comparative Example 6

[0083] Refer to the method of Comparative Example 5 for operation, the difference being that the amount of MAH-GO dispersion used in this comparative example is 12.5 parts by mass.

[0084] Comparative Example 7

[0085] In this comparative example, hyperbranched polyamide modified graphene oxide (HPA-GO) is used instead of silane coupling agent modified graphene oxide, specifically as follows:

[0086] (1) Add 10 parts by mass of diethylenetriamine and 10 parts by mass of acrylate into a three-necked flask. The three-necked flask is equipped with a magnetic stirrer and a condensing reflux device, and continuously stir and react in an ice-water bath (0 - 5 °C) for 12 h. Then add 1 part by mass of ethylenediamine to the obtained system, heat to 70 °C and react for 1 h, and then heat to 130 °C and react for 7 h to obtain hyperbranched polyamide (HPA);

[0087] (2) Add 30 mL of GO dispersion (the dispersant is DMF, with a concentration of 10 mg / mL, and the size of GO is 8 - 10 μm; the GO dispersion is purchased from Hangzhou Gaoxi Technology Co., Ltd., model GO1-DMF), 90 mL of DMF, and 3 g of HPA into a three-necked flask, and react at 100 °C for 24 h; after the reaction, wash and centrifuge the obtained product system with DMF to remove the unreacted HPA, and collect the solid material, which is HPA-GO. Mix the HPA-GO with DMF to obtain an HPA-GO dispersion with a concentration of 2 mg / mL;

[0088] (3) Add 30 parts by mass of diphenyl bismaleimide and 30 parts by mass of DMF into a flask, and ultrasonically dissolve the diphenyl bismaleimide for 30 min under the condition of a power of 300 W. Then add 5 parts by mass of the above-mentioned HPA-GO dispersion at 50 °C, and stir and react at a rotation speed of 2000 r / min for 1.5 h; after the reaction, add 80 parts by mass of diphenyl bismaleimide to the obtained product system, and stir and mix at a rotation speed of 2000 r / min for 1.5 h to obtain a premixed liquid;

[0089] (4) Refer to the methods in steps (3) - (6) of Example 1 for operation, and use the above-mentioned premixed liquid to prepare HPA-GO modified BMI resin.

[0090] Comparative Example 8

[0091] Refer to the method of Comparative Example 7 for operation, the difference is that the dosage of HPA-GO dispersion in this comparative example is 12.5 parts by mass.

[0092] Test Example 1

[0093] Perform performance tests on the BMI resins prepared in each example and comparative example. The results are shown in Table 1. Among them, the flexural strength is tested according to the method of GB / T2567-2021, and the flexural modulus is tested according to the method of GB / T2567-2021. It can be seen from Table 1 that in the examples of the present invention, by using KH550 to modify GO, ball milling treatment, and solvent replacement, compared with Comparative Examples 1 - 4, the mechanical properties (flexural strength, flexural modulus) and heat resistance (glass transition temperature, 5% thermal decomposition temperature) of the BMI resin can be significantly improved, proving that KH550 modified GO plays a role in toughening, strengthening, and improving the heat resistance of the BMI resin; compared with using maleic anhydride or hyperbranched polyamide to modify GO in Comparative Examples 5 - 8, using KH550 to modify GO in the examples of the present invention can effectively improve the comprehensive performance of the BMI resin.

[0094] Table 1 Performance test results of BMI resins prepared in each example and comparative example

[0095]

[0096]

[0097] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a bismaleimide resin functionalized with a silane coupling agent, comprising the following steps: Mixing graphene oxide, a silane coupling agent, a first organic solvent and water, and performing a first modification treatment to obtain silane coupling agent-modified graphene oxide; The silane coupling agent-modified graphene oxide, the second organic solvent and part of bismaleimide are mixed to perform a second modification treatment, and the obtained second modified product system is mixed with the remaining bismaleimide to obtain a premix liquid; the second organic solvent is a good solvent for bismaleimide; The premix liquid is subjected to ball milling treatment to obtain a ball milled liquid; The ball mill liquid is mixed with a poor solvent of bismaleimide, and the solvent is replaced to obtain a modified mixed powder; The modified mixed powder is mixed with a cross-linking agent to carry out a cross-linking reaction to obtain a prepolymer; The prepolymer is cured to obtain the silane coupling agent functionalized graphene oxide modified bismaleimide resin.

2. The preparation method according to claim 1, characterized in that: The silane coupling agent is γ-aminopropyltriethoxysilane; the temperature of the first modification treatment is 50-80° C., and the time is 12-36 hours.

3. The preparation method according to claim 1, characterized in that: The second organic solvent includes N,N-dimethylformamide or N-methylpyrrolidone; the poor solvent for bismaleimide includes water or ethanol.

4. The preparation method according to claim 1 or 3, characterized in that: The silane coupling agent modified graphene oxide, the second organic solvent and part of bismaleimide are mixed, comprising: The part of bismaleimide and the part of the second organic solvent are first mixed to obtain a bismaleimide solution; The silane coupling agent modified graphene oxide is mixed with the remaining second organic solvent to obtain a silane coupling agent modified graphene oxide dispersion; The bismaleimide solution and the silane coupling agent modified graphene oxide dispersion are mixed for the third time.

5. The preparation method according to claim 4, characterized in that: The mass of the part of bismaleimide is 10-30% of the total mass of bismaleimide; the mass ratio of the part of bismaleimide to the part of the second organic solvent is 10:8-50; the concentration of the silane coupling agent modified graphene oxide dispersion is 1-5 mg / mL; the ratio of the mass of the silane coupling agent modified graphene oxide dispersion to the total mass of bismaleimide is 0.1-20:

110.

6. The preparation method according to claim 1, characterized in that: The temperature of the second modification treatment is 30-60° C. and the time is 1-2 hours.

7. The preparation method according to claim 1, characterized in that: The ball milling process is performed at a rotation speed of 200 to 800 r / min and for a time of 2 to 8 hours.

8. The preparation method according to claim 1, characterized in that: The cross-linking agent comprises diallyl bisphenol A, and the ratio of the mass of the cross-linking agent to the total mass of bismaleimide is 91-110; the temperature of the cross-linking reaction is 110-140° C., and the time is 1-2 hours.

9. Silane coupling agent functionalized graphene oxide modified bismaleimide resin prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the bismaleimide resin modified by graphene oxide functionalized with a silane coupling agent as claimed in claim 9 in structural composite materials.

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