A graphene-polyimide composite resin and its preparation method

Abstract

This invention discloses a graphene-polyimide composite resin and its preparation method. Graphene, dianhydride, and diamine are polymerized in a non-polar solvent, and after filtration and drying into powder, a graphene-polyimide composite resin precursor powder is obtained. The graphene-polyimide composite resin is then obtained by hot pressing. This invention generates a composite material through the polymerization reaction of graphene, dianhydride, and diamine in a non-polar solvent. The graphene is uniformly dispersed and has a high content. The entire synthesis process is convenient, the molding speed is fast, and the product has low shrinkage, few defects, and good mechanical properties. It can directly mold complex shapes and thick-walled products, and can produce high-value-added products with special functions.

Description

Technical Field

[0001] This invention relates to a graphene-polyimide composite resin and its preparation method, belonging to the field of polymer resin technology. Background Technology

[0002] Since its synthesis in 1908, polyimide (PI) has become a well-known high-performance polymer, serving as a specialized engineering material with superior heat resistance, mechanical properties, and electrical properties unmatched by other polymers. Combining it with nanomaterials further enhances these properties. Compared to films reinforced with nanofibers or nanoparticles, sheet-like or layered reinforcing materials better demonstrate the reinforcing effect of polyimide and its composites. Graphene, with its excellent physical and chemical properties, is a good reinforcing material for composites. Studies have shown that combining graphene with polyimide inevitably results in a directional enhancement of the material's thermal stability, mechanical properties, and electrical conductivity. Furthermore, due to graphene's perfect two-dimensional structure, it can exert a planar induction effect on polyimide, causing significant orientation on the graphene surface. This alleviates the internal stress generated during the curing process of polyimide, improves the fracture toughness of the carbonized products, and also enhances physical properties such as electrical conductivity.

[0003] Existing technologies disclose various graphene-polyimide composite materials and their preparation methods, mainly including two types: mechanical blending and in-situ polymerization. Both methods require the liquid-phase synthesis of dianhydride diamine in polar solvents such as N,N-dimethylacetamide or N-methylpyrrolidone, followed by processing into graphene-polyimide composite materials. This method is generally used to prepare polyimide films and other products. To prepare resin blocks, polyamic acid needs to be extracted from the solution, and further additives such as catalysts and dehydrating agents are required. Complex procedures such as anti-solvent methods or spray drying are then used to extract the graphene-polyimide components. After extraction, the materials need to be ground and crushed before further use. The solvents used in the existing liquid-phase methods are themselves toxic and cannot be fully recycled, posing a threat to the environment and human health. More importantly, in the process of graphene and polyimide composite, since graphene composite polyamic acid is required as a precursor, if polyamic acid can be dissolved in a large amount in the solvent, the graphene composite polyamic acid composite produced by the polymerization reaction will dissolve, and a large amount of graphene will agglomerate and cannot be effectively dispersed. Therefore, it is impossible to effectively increase the graphene content in the composite, which limits the final performance of the prepared product. Summary of the Invention

[0004] To address the problems in the existing technology, the present invention aims to overcome the shortcomings of the existing technology and provide a graphene-polyimide composite resin and its preparation method. The method involves first preparing graphene-polyimide composite resin precursor powder, and then preparing the graphene-polyimide composite resin. The process is convenient, the molding speed is fast, the production efficiency is accelerated, and the product has low shrinkage, few defects, and good mechanical properties.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a graphene-polyimide composite resin includes the following steps:

[0007] a. Preparation of graphene-polyimide composite resin precursor powder:

[0008] Graphene, dianhydride, and diamine were polymerized in a nonpolar solvent to obtain a prepolymer suspension; the prepolymer suspension was then filtered and dried into powder to obtain graphene-polyimide composite resin precursor powder.

[0009] b. Preparation of graphene-polyimide composite resin:

[0010] The graphene-polyimide composite resin precursor powder prepared in step a is subjected to a hot pressing molding method to obtain the graphene-polyimide composite resin.

[0011] This invention first prepares graphene-polyimide composite resin precursor powder by means of the following method: graphene, aromatic dianhydride and diamine are polymerized in a nonpolar organic solvent to obtain a graphene-polyamic acid suspension; the graphene-polyamic acid suspension is filtered, the precipitated powder is dried to obtain graphene-polyimide composite resin precursor powder; then the graphene-polyimide composite resin is obtained by hot pressing.

[0012] This invention prepares graphene-polyimide composite resin by polymerizing graphene, dianhydride, and diamine in a non-polar solvent. The process is convenient, the molding speed is fast, and the production efficiency is accelerated. The product has low shrinkage, few defects, and good mechanical properties. It can be directly molded into complex shapes and thick-walled products, and can produce high value-added products with special functions.

[0013] Preferably, in step a, the graphene is at least one of single-layer graphene, few-layer graphene, and multilayer graphene. Few-layer graphene is preferred.

[0014] Preferably, in step a, the dianhydride and diamine are mixed in a molar ratio of 1:1.

[0015] Preferably, in step a, when mixing graphene, dianhydride, and diamine, the weight of graphene is 4 parts by weight, and the combined weight of dianhydride and diamine is 1-4000 parts by weight. The preferred proportions are: 4 parts graphene, and 14 parts dianhydride and diamine.

[0016] Preferably, in step a, the graphene, dianhydride, and diamine are added to a nonpolar solvent, and the polymerization reaction is carried out by reflux under an inert atmosphere.

[0017] Preferably, in step a, the polymerization temperature is controlled at 130-200°C, and the polymerization time is 6-10 hours. More preferably, the polymerization time is 6-8 hours.

[0018] Preferably, in step a, the mixing ratio of dianhydride and nonpolar solvent is: 0.02 mol of dianhydride is mixed with at least 300 ml of nonpolar solvent; or, 0.02 mol of diamine is mixed with at least 300 ml of nonpolar solvent.

[0019] Preferably, in step a, the filtration is performed using a Buchner funnel, followed by vacuum drying at a temperature not exceeding 250°C, and the powder is collected to obtain graphene-polyimide composite resin precursor powder. More preferably, the powder is filtered using a Buchner funnel and then dried in a vacuum drying oven at 200-230°C for at least 24 hours to obtain a solid powder, which is the graphene-polyimide composite resin precursor powder.

[0020] Preferably, in step a, the dianhydride is an aromatic dianhydride.

[0021] Preferably, in step a, the dianhydride is at least one selected from 2,3,3',4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxophthalic anhydride (ODPA), bisphenol A diether dianhydride (BPADA), and pyromellitic dianhydride (PMDA). 2,3,3',4'-biphenyltetracarboxylic dianhydride (BPDA) is preferred.

[0022] Preferably, in step a, the diamine is an aromatic diamine.

[0023] Preferably, in step a, the diamine is at least one of 4,4′-diaminodiphenylmethane (4,4′-MDA), 4,4′-diaminodiphenyl ether (4,4′-ODA), and 1,3-bis(4-aminophenoxybenzene) (TPE-R). 4,4′-diaminodiphenyl ether (4,4′-ODA) is preferred.

[0024] Preferably, in step a, the nonpolar solvent is at least one selected from toluene, o-xylene, p-xylene, m-xylene, butyl acetate, and chlorobenzene. o-xylene is preferred. This invention selects a nonpolar solvent that can azeotropically react with water. During the dehydration condensation of dianhydride and diamine to form polyamic acid, the water produced evaporates along with the nonpolar solvent such as xylene and is removed during reflux condensation.

[0025] Preferably, in step b, the hot pressing process comprises the following steps:

[0026] Graphene-polyimide composite resin precursor powder is spread evenly in a mold and placed in a flat vulcanizing machine. Hot pressing is performed at 280-400°C, above the melting point of the polymer powder, with a holding pressure of 1-20 MPa for 10-60 minutes. The mixture is then rapidly cooled, and removed when cooled to room temperature to obtain the graphene-polyimide composite resin material. More preferably, during hot pressing, a holding pressure of 6-18 MPa is applied for 20-60 minutes. More preferably, rapid cooling is performed, and the material is removed when cooled to room temperature to obtain the graphene-polyimide composite resin material.

[0027] A graphene-polyimide composite resin is prepared using the preparation method of the graphene-polyimide composite resin of the present invention.

[0028] Existing technologies cannot prepare graphene-polyimide composite resins with high graphene content and dispersion, and their performance falls far short of the theoretical performance expected of graphene-polyimide composite resins. This invention utilizes a solvent that does not react with the generated graphene-polyimide composite resin precursor and involves no dissolution process, allowing for recycling and minimizing environmental pollution. This invention first synthesizes graphene-polyimide composite resin precursor powder, followed by hot pressing. This results in rapid product molding, uniform graphene distribution and high content, good stability, and the ability to directly mold complex shapes and thick-walled products, as well as produce high-value-added products with special functions.

[0029] The present invention has the following obvious and prominent substantive features and significant advantages:

[0030] 1. In this invention, graphene-polyimide composite resin precursor powder is first synthesized, and then hot-pressed. The graphene is evenly distributed and has a high content, and has good stability.

[0031] 2. This invention can directly mold complex shapes and thick-walled products, enabling the production of high-value-added products with special functions;

[0032] 3. The solvent used in this invention does not react with the products in the reaction process and has no dissolution process, so it can be recycled and has little environmental pollution. Attached Figure Description

[0033] Figure 1 This is a physical image of the graphene-polyimide composite resin material prepared in Example 1 of the present invention.

[0034] Figure 2 The typical stress-strain mechanical curves are those of the graphene-polyimide composite resin prepared in Example 1 of this invention. Detailed Implementation

[0035] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0036] Example 1

[0037] In this embodiment, a method for preparing a graphene-polyimide composite resin includes the following steps:

[0038] a. Preparation of graphene-polyimide composite resin precursor powder:

[0039] In a 500 mL three-necked flask, 0.1 g of monolayer graphene, 0.02 mol of 4,4′-diaminodiphenyl ether (ODA), 0.02 mol of bisphenol A diether dianhydride (BPADA), and 300 mL of o-xylene were added. Under an inert atmosphere, the mixture was heated to 130 °C and stirred thoroughly. The mixture was then refluxed to carry out the polymerization reaction. After 6 hours of reaction, a prepolymer suspension was obtained. To ensure complete end-capping, the prepolymer suspension was cooled to room temperature, filtered through a Büchner funnel, and dried in a vacuum drying oven at 230 °C for 24 hours. The solid powder was collected to obtain graphene-polyimide composite resin precursor powder.

[0040] b. Process for preparing and synthesizing graphene-polyimide composite resin using hot pressing:

[0041] Take the graphene-polyimide composite resin precursor powder prepared in step a, spread it evenly in a mold, place it in a flat vulcanizing machine, and hot press it at 360°C. Hold it under a load of 6MPa for 20 minutes, then cool it down rapidly. When it cools to room temperature, take it out to obtain the graphene-polyimide composite resin material.

[0042] Example 2

[0043] This embodiment is basically the same as Embodiment 1, except that:

[0044] In this embodiment, a method for preparing a graphene-polyimide composite resin includes the following steps:

[0045] a. Preparation of graphene-polyimide composite resin precursor powder:

[0046] In a 500 mL three-necked flask, 10 g of few-layer graphene, 0.02 mol of 4,4′-diaminodiphenyl ether (ODA), 0.02 mol of 2,3,3',4'-biphenyltetracarboxylic dianhydride (BPDA), and 300 mL of o-xylene were added. Under an inert atmosphere, the mixture was heated to 170 °C and stirred thoroughly. The mixture was then refluxed to carry out the polymerization reaction. After 8 hours of reaction, a prepolymer suspension was obtained. To ensure complete end-capping, the prepolymer suspension was cooled to room temperature, filtered through a Büchner funnel, and dried in a vacuum drying oven at 200 °C for 24 hours. The solid powder was collected to obtain graphene-polyimide composite resin precursor powder.

[0047] b. Process for preparing and synthesizing graphene-polyimide composite resin using hot pressing:

[0048] Take the graphene-polyimide composite resin precursor powder prepared in step a, spread it evenly in a mold, place it in a flat vulcanizing machine, and hot press it at 280°C with a load of 12MPa for 40 minutes. Then cool it down rapidly and take it out when it cools to room temperature to obtain the graphene-polyimide composite resin material.

[0049] Example 3

[0050] This embodiment is basically the same as the previous embodiments, except that:

[0051] In this embodiment, a method for preparing a graphene-polyimide composite resin includes the following steps:

[0052] a. Preparation of graphene-polyimide composite resin precursor powder:

[0053] In a 500 mL three-necked flask, 40 g of multilayer graphene, 0.02 mol of 4,4′-diaminodiphenyl ether (ODA), 0.02 mol of 4,4′-oxydiphthalic anhydride (ODPA), and 300 mL of o-xylene were added. Under an inert atmosphere, the mixture was heated to 200 °C and stirred thoroughly. The mixture was then refluxed to carry out the polymerization reaction. After 8 hours of reaction, a prepolymer suspension was obtained. To ensure complete end-capping, the prepolymer suspension was cooled to room temperature, filtered through a Büchner funnel, and dried in a vacuum drying oven at 230 °C for 24 hours. The solid powder was collected to obtain graphene-polyimide composite resin precursor powder.

[0054] b. Process for preparing and synthesizing graphene-polyimide composite resin using hot pressing:

[0055] Take the graphene-polyimide composite resin precursor powder prepared in step a, spread it evenly in a mold, place it in a flat vulcanizing machine, hot press it at 400°C, hold it under a load of 18MPa for 60 minutes, then cool it down rapidly. When it cools down to below 100°C, take it out to obtain the graphene-polyimide composite resin material.

[0056] Example 4

[0057] This embodiment is basically the same as the previous embodiments, except that:

[0058] In this embodiment, in step a, the graphene is at least one of single-layer graphene, few-layer graphene, and multilayer graphene, and a mixture of single-layer graphene.

[0059] In this embodiment, in step a, the dianhydride is pyromellitic dianhydride (PMDA), or a mixture of at least one of 2,3,3',4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxophthalic anhydride (ODPA), bisphenol A diether dianhydride (BPADA) and pyromellitic dianhydride (PMDA).

[0060] The diamine is at least one of 4,4′-diaminodiphenylmethane (4,4′-MDA) and 1,3-bis(4-aminophenoxybenzene) (TPE-R), or a mixture of at least one of 4,4′-diaminodiphenylmethane (4,4′-MDA) and 1,3-bis(4-aminophenoxybenzene) and 4,4′-diaminodiphenyl ether (4,4′-ODA);

[0061] The nonpolar solvent is at least one of toluene, p-xylene, m-xylene, butyl acetate, and chlorobenzene, or a mixture of at least one of toluene, p-xylene, m-xylene, butyl acetate, and chlorobenzene and o-xylene.

[0062] In this embodiment, graphene, aromatic dianhydride, and aromatic diamine are polymerized in a nonpolar solvent to obtain graphene-polyimide composite resin precursor powder. The graphene-polyimide composite resin is then obtained through hot pressing. This embodiment offers fast molding speed, increasing production efficiency, and produces products with low shrinkage, few defects, and high mechanical properties. Furthermore, this embodiment can directly mold complex shapes and thick-walled products, enabling the production of high-value-added products with special functions.

[0063] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a graphene-polyimide composite resin, characterized in that, Includes the following steps: a. Preparation of graphene-polyimide resin precursor powder: Graphene powder, dianhydride, and diamine were polymerized in a nonpolar solvent to obtain a prepolymer suspension; the prepolymer suspension was then filtered and dried into powder to obtain graphene-polyimide resin precursor powder. b. Preparation of graphene-polyimide composite materials: The graphene-polyimide precursor powder prepared in step a is subjected to hot pressing to obtain a graphene-polyimide composite material.

2. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: The graphene is at least one of single-layer graphene, few-layer graphene, and multilayer graphene.

3. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: In step a, the polymerization temperature is controlled at 130-200℃, the polymerization time is 6-10h, and the Buchner funnel is used for filtration. The powder is then collected at a temperature not exceeding 250℃ to obtain graphene-polyimide resin precursor powder.

4. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: In step a, dianhydride and diamine are added to a nonpolar solvent at a molar ratio of 1:1, graphene is added at 4 parts by weight, and the total weight of dianhydride and diamine is added at 1-4000 parts by weight. The polymerization reaction is carried out under an inert atmosphere and refluxed.

5. The method for preparing the graphene-polyimide composite resin according to claim 4, characterized in that: The graphene is in the amount of 4 parts by weight, and the dianhydride and diamine together are in the amount of 14 parts by weight.

6. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: In step a, the dianhydride is at least one of 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, bisphenol A type diether dianhydride, and pyromellitic dianhydride.

7. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: In step a, the diamine is at least one of 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, and 1,3-bis(4-aminophenoxybenzene).

8. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: In step a, the nonpolar solvent is at least one of toluene, o-xylene, p-xylene, m-xylene, butyl acetate, and chlorobenzene.

9. The method for preparing the graphene-polyimide composite resin according to claim 1, characterized in that: In step b, the hot pressing process includes the following steps: The graphene-polyimide composite resin precursor powder is spread evenly in a mold, placed in a flat vulcanizing machine, and hot-pressed at 280-400℃ with a load of 1-20MPa for 10-60 minutes. Then it is rapidly cooled and removed when cooled to room temperature to obtain the graphene-polyimide composite resin material.

10. A graphene-polyimide composite resin, characterized in that: It is prepared by the method described in claim 1 for preparing graphene-polyimide composite resin.

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