Modified graphene / PMIA nano composite material and preparation method thereof

Abstract

The invention provides a modified graphene / PMIA nano composite material and a preparation method thereof, and relates to the field of electromagnetic shielding materials, the preparation method comprises the following steps: S1, adding a modifier into an aqueous dispersion of graphene oxide, and carrying out solid-liquid separation and drying to obtain modified graphene oxide powder; s2, adding the modified graphene oxide powder into a solvent, dispersing to a uniform state, standing, and taking upper-layer dispersion liquid; s3, adding lithium salt into the dispersion liquid until the lithium salt is fully dissolved; s4, adding PMIA short fibers into the dispersion liquid, and heating and dissolving the PMIA short fibers to prepare a spinning solution; s5, spinning by adopting a wet spinning process to prepare a wet film, and removing the solvent to obtain a graphene / PMIA nano composite material; the graphene oxide is subjected to specific process steps including a specific modification process, alcohol washing and the like, the composite material obtained after the modified graphene oxide and the PMIA short fibers are combined is tighter, and the electromagnetic shielding effectiveness can reach 50 dB; the whole process is simpler, the raw material selectivity is wide, and the process is not limited by the structural form of raw material fiber bundles.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding nanocomposite materials, and in particular to a modified graphene / PMIA nanocomposite material and a preparation method thereof. Background Art

[0002] Poly(m-phenylene isophthalamide) (PMIA) is a meta-aromatic polyamide first synthesized in 1962. Due to its excellent high-temperature resistance and flame retardancy, PMIA-based high-temperature insulating paper products and fibers are widely used in related industries and clothing.

[0003] Electromagnetic shielding isolates an object from external electromagnetic fields, preventing electromagnetic waves from damaging the object's interior. It also absorbs electromagnetic wavelengths, preventing them from reflecting back, thus achieving "invisibility." Graphene, a two-dimensional material composed of a single layer of carbon atoms, has a unique structure that allows electromagnetic waves to move along specific paths, achieving electromagnetic shielding. However, graphene nanosheets themselves are prone to brittle fracture. Therefore, the combination of graphene and other materials is a research trend in electromagnetic shielding materials.

[0004] In the prior art, Chinese invention patent application CN108794812A discloses an electromagnetic shielding material obtained by dispersing a graphene-biochar composite filler in a polymer matrix. The resulting electromagnetic shielding material has an electrical conductivity of up to 50 S / m and an electromagnetic shielding effectiveness of approximately 50 dB for 8-12 GHz waves. The graphene content is relatively low, more than an order of magnitude lower than that of electromagnetic shielding materials using pure graphene as a filler. This method reduces the amount of graphene added to the electromagnetic shielding material, thereby reducing costs. However, in some applications where graphene is used solely as a modifier to modify polymers (considering that the use of other fillers may negatively impact certain aspects of the resulting composite product's performance), as described in paragraph 0110 of the specification, the graphene filler obtained by omitting the biochar component and applying it to the polymer suffers from poor conductivity and shielding performance due to the graphene's tendency to agglomerate and difficulty in dispersion.

[0005] In addition, in the prior art, a Chinese invention patent application with publication number CN107630352A discloses a graphene-reinforced meta-aromatic polyamide fiber bundle and a preparation method thereof, which adopts the method of hydrolyzing the fiber and modifying it with diisocyanate to make the fiber surface have active groups, adding the wrinkled graphene oxide to the strong alkaline DMSO to maintain the original morphology, and the surface hydroxyl groups react with the isocyanate to form a covalent bond, thereby obtaining a fiber bundle with surface grafted graphene oxide microspheres, and then high-temperature treatment to obtain a porous graphene microsphere-reinforced meta-aromatic polyamide fiber bundle, whose performance indicators are as follows: tensile strength reaches 2.96 cN / dtex, surface resistance reaches 10 6 This method aims to improve the tensile strength of the fiber bundle to a certain extent, but the increase is limited (about 22% compared to Comparative Example 1); the process requires two-step fiber processing, which is relatively complex; and its raw material selection is limited, such as the necessity of using a fiber bundle structure.

[0006] Therefore, the present application aims to propose a modified graphene-PMIA composite nanofiber material and its preparation method, which has a simpler process, a wide range of raw material selectivity, and good tensile strength and electromagnetic shielding performance. Summary of the Invention

[0007] In view of the above problems existing in the prior art, the present invention provides a modified graphene / PMIA nanocomposite material and a preparation method thereof.

[0008] The technical solution of the present invention to solve the above technical problems is as follows:

[0009] A method for preparing a modified graphene / PMIA nanocomposite material, characterized by comprising the following steps:

[0010] S1, adding a modifier to the aqueous dispersion of graphene oxide, separating the solid and liquid, and drying to obtain modified graphene oxide powder;

[0011] S2, adding the modified graphene oxide powder obtained in S1 to a solvent and dispersing it until it is uniform, letting it stand, and taking the upper layer of the dispersion;

[0012] S3. Adding a lithium salt to the dispersion obtained in S2 until fully dissolved; the lithium salt is lithium chloride, lithium bromide, or lithium nitrate; the lithium salt such as lithium chloride is used to generate a specific interaction with the solvent molecules to change the properties of the solvent, thereby making the solvation layer around the subsequently added PMIA molecular chain more stable and reducing the interaction between PMIA molecules, thereby making PMIA easier to dissolve and facilitating subsequent uniform mixing with graphene oxide;

[0013] S4, adding PMIA staple fibers to the dispersion obtained in S3, and heating to dissolve them to prepare a spinning solution;

[0014] S5. A wet spinning process is used to spin a wet film, and the wet film is heat-treated to remove the solvent to obtain a graphene / PMIA nanocomposite material.

[0015] Due to its strong hydrophilicity, graphene oxide is typically produced by spray drying in the prior art, which requires a spray dryer and has low production efficiency. However, the present invention uses a modifier to modify graphene oxide, making it easier to separate from water and avoiding the need for a spray dryer.

[0016] Furthermore, in step S1:

[0017] The modifier is PEI polyethyleneimine or PAM polyacrylamide;

[0018] After solid-liquid separation, the solid phase was washed with ethanol and then dried.

[0019] The amount of the modifier added relative to the graphene oxide is 10%-25%.

[0020] Furthermore, in step S2: the solvent is a mixture of DMAC and DMF, to which a dispersant is added. The dispersant is a high molecular weight block copolymer containing amine anchoring groups or a medium polarity hyperdispersant, preferably Winsperes 7050 or 3050.

[0021] The modified graphene oxide is extremely hard and severely agglomerated after drying. This process uses ethanol washing after modification to make the dried powder fluffy and soft, and can be directly ultrasonically dispersed and evenly used with solvents such as DMF and DMAC.

[0022] Furthermore, in step S3:

[0023] The amount of lithium chloride added is 60%-75% of graphene oxide;

[0024] The weight of PMIA staple fibers is 5-12.5 times that of modified graphene oxide powder;

[0025] Furthermore, in step S5:

[0026] Heat treatment temperature is 150℃-200℃;

[0027] The heat treatment is carried out in a high-pressure reactor at a pressure of 1-3 MPa.

[0028] And the modified graphene / PMIA nanocomposite material prepared by the above preparation method.

[0029] The beneficial effects of the present invention are as follows: by subjecting graphene oxide to specific process steps, including a specific modification process (specific modifier and solvent) and alcohol washing, the composite material obtained by combining the modified graphene oxide with PMIA staple fibers is more compact, and can be used as a nano-electromagnetic shielding material with higher mechanical properties, stronger tensile strength, greater friction resistance, longer high-temperature resistance, and good electromagnetic shielding function, with an electromagnetic shielding efficiency of up to 50dB; moreover, the overall process method is simpler, the raw material selectivity is wide, and it is not limited to the structural form of the raw material fiber bundle. DETAILED DESCRIPTION

[0030] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0031] The main raw materials and specifications of the following examples and comparative examples are as follows:

[0032] Graphene oxide filter cake, solid content 44.37%, produced by Shandong Lit Nano Technology Co., Ltd.;

[0033] PEI (polyethyleneimine), 50% aqueous solution with a molecular weight of 70,000, produced by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0034] PAM (polyacrylamide), molecular weight 5 million to 8 million, anionic, produced by Anhui Tianrun Chemical Industry Co., Ltd.;

[0035] DMAC (N,N-dimethylacetamide), purity ≥99.9%, produced by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0036] DMF (N,N-dimethylformamide), purity ≥99.9%, produced by Sinopharm Chemical Reagent Co., Ltd.;

[0037] WinSperse 3050 dispersant, produced by WinSperse New Materials (Shandong) Co., Ltd.

[0038] WinSperse 7050 dispersant, produced by WinSperse New Materials (Shandong) Co., Ltd.

[0039] PMIA fiber, fineness 1.5dtex, length 38mm, produced by Yantai Taihe New Materials Co., Ltd.

[0040] In the following examples, the usage ratios of the materials involved, unless otherwise specified, refer to the mass ratios; the concentrations involved, unless otherwise specified, refer to the mass concentrations.

[0041] Example 1

[0042] The preparation method of the modified graphene / PMIA nanocomposite material of this embodiment is carried out according to the following steps:

[0043] S1. Preparing a graphene oxide dispersion: dispersing the graphene oxide filter cake in water by high-speed shearing to prepare a graphene oxide dispersion with a concentration of 2.5%;

[0044] Preparation of modified graphene oxide: adding a modifier PEI (the addition amount is 18% of the solid content of graphene oxide) thereto, filtering, then washing the filter cake with ethanol and filtering again, and drying the filter cake at 50° C. to obtain modified graphene oxide powder;

[0045] S2. Prepare solvent: add dispersant WinSperse 3050 to the mixture of DMAC and DMF (the ratio of the two is 1:1), the amount of dispersant is 0.25% of the solid content of graphene oxide, and ultrasonically disperse until uniform;

[0046] The modified graphene oxide powder obtained in S1 was added to the prepared solvent and dispersed until uniform. The mixture was allowed to stand for one day and the upper dispersion was collected.

[0047] S3. Add lithium chloride to the dispersion obtained in S2, wherein the amount of lithium chloride added is 65% of the solid content of graphene oxide, and stir at room temperature for 2 hours to fully dissolve it;

[0048] S4. Take the dried PMIA fibers, cut them into short fibers, add the PMIA short fibers to the dispersion obtained in S3, wherein the weight of the PMIA short fibers is 8 times that of the modified graphene oxide powder, and dissolve them in a 70°C water bath with stirring for 2 hours to prepare a spinning solution;

[0049] S5. A wet spinning process is adopted. The spinning equipment includes a spinneret, a coagulation bath and a winding device, which are used to spin the spinning solution into a film and then wind it. A high-pressure spinneret is used to rotate back and forth on a roller wrapped with release paper to spin a compact wet film. The wet film is placed in a high-pressure reactor at 2 MPa and heat-treated at 150°C to remove the solvent, thereby obtaining a graphene / PMIA nanocomposite material.

[0050] Example 2

[0051] The preparation method of the modified graphene / PMIA nanocomposite material of this embodiment is carried out according to the following steps:

[0052] S1. Preparing a graphene oxide dispersion: dispersing the graphene oxide filter cake in water by high-speed shearing to prepare a graphene oxide dispersion with a concentration of 0.1%;

[0053] Preparation of modified graphene oxide: adding a modifier PEI (the addition amount is 10% of the solid content of graphene oxide) thereto, filtering, then washing the filter cake with ethanol and filtering again, and drying the filter cake at 50° C. to obtain modified graphene oxide powder;

[0054] S2. Prepare solvent: add dispersant WinSperse 3050 to the mixture of DMAC and DMF (the ratio of the two is 1:1), the amount of dispersant is 0.1% of the solid content of graphene oxide, and ultrasonically disperse until uniform;

[0055] The modified graphene oxide powder obtained in S1 was added to the prepared solvent and dispersed until uniform. The mixture was allowed to stand for one day and the upper dispersion was collected.

[0056] S3. Add lithium chloride to the dispersion obtained in S2, wherein the amount of lithium chloride added is 60% of the solid content of graphene oxide, and stir at room temperature for 2 hours to fully dissolve it;

[0057] S4. Take the dried PMIA fibers, cut them into short fibers, add the PMIA short fibers to the dispersion obtained in S3, wherein the weight of the PMIA short fibers is 5 times that of the modified graphene oxide powder, and dissolve them in a 60°C water bath with stirring for 2 hours to prepare a spinning solution;

[0058] S5. A wet spinning process is adopted. The spinning equipment includes a spinneret, a coagulation bath and a winding device, which are used to spin the spinning solution into a film and then wind it. A high-pressure spinneret is used to rotate back and forth on a roller wrapped with release paper to spin a compact wet film. The wet film is placed in a high-pressure reactor at 1 MPa and heat-treated at 150°C to remove the solvent, thereby obtaining a graphene / PMIA nanocomposite material.

[0059] Example 3

[0060] The preparation method of the modified graphene / PMIA nanocomposite material of this embodiment is carried out according to the following steps:

[0061] S1. Preparing a graphene oxide dispersion: dispersing the graphene oxide filter cake in water by high-speed shearing to prepare a graphene oxide dispersion with a concentration of 5%;

[0062] Preparation of modified graphene oxide: adding a modifier PAM (the addition amount is 25% of the solid content of graphene oxide) thereto, filtering, then washing the filter cake with ethanol and filtering again, and drying the filter cake at 50° C. to obtain modified graphene oxide powder;

[0063] S2. Prepare solvent: add dispersant WinSperse 7050 to the mixture of DMAC and DMF (the ratio of the two is 1:1), the amount of dispersant is 0.5% of the solid content of graphene oxide, and ultrasonically disperse until uniform;

[0064] The modified graphene oxide powder obtained in S1 was added to the prepared solvent and dispersed until uniform. The mixture was allowed to stand for one day and the upper dispersion was collected.

[0065] S3. Add lithium chloride to the dispersion obtained in S2, wherein the amount of lithium chloride added is 75% of the solid content of graphene oxide, and stir at room temperature for 2 hours to fully dissolve it;

[0066] S4. Take the dried PMIA fibers, chop them into short fibers, add the PMIA short fibers to the dispersion obtained in S3, wherein the weight of the PMIA short fibers is 12.5 times that of the modified graphene oxide powder, and dissolve them in a 75°C water bath with stirring for 2 hours to prepare a spinning solution;

[0067] S5. A wet spinning process is adopted. The spinning equipment includes a spinneret, a coagulation bath and a winding device, which are used to spin the spinning solution into a film and then wind it. A high-pressure spinneret is used to rotate back and forth on a roller wrapped with release paper to spin a compact wet film. The wet film is placed in a high-pressure reactor at 3 MPa and heat-treated at 150°C to remove the solvent, thereby obtaining a graphene / PMIA nanocomposite material.

[0068] Comparative Example 1

[0069] This comparative example uses unmodified PMIA fibers, that is, the raw PMIA fibers used in step S4 of Example 1.

[0070] Comparative Example 2

[0071] The preparation method of the nanocomposite material of this comparative example is basically the same as that of Example 1, except that the modifier in step S1 is replaced by an equal mass of SDS.

[0072] The experimental results show that SDS has poor dispersion due to weak binding force with graphene oxide.

[0073] Comparative Example 3

[0074] The preparation method of the nanocomposite material of this comparative example is basically the same as that of Example 1, except that the mixed solution of DMAC and DMF in step S2 is replaced by an equal mass of DMAC alone.

[0075] Comparative Example 4

[0076] The preparation method of the nanocomposite material of this comparative example is basically the same as that of Example 1, except that the mixed solution of DMAC and DMF in step S2 is replaced by an equal mass of DMF alone.

[0077] Comparative Example 5

[0078] The preparation method of the nanocomposite material in this comparative example is basically the same as that in Example 1, except that the filter cake is not washed with ethanol in step S2, that is, it is dried immediately after filtration.

[0079] The experimental results show that the dried graphene oxide is very hard and cannot be evenly dispersed in the DMAC and DMF mixture. It separates into layers after standing, and the upper layer is a transparent clear liquid that contains no or trace amounts of graphene oxide.

[0080] Comparative Example 6

[0081] The preparation method of the nanocomposite material in this comparative example is basically the same as that in Example 1, except that the ethanol in step S2 is replaced by water.

[0082] The experimental results show that the difficulty of filtration increases significantly, and the graphene oxide is very hard after drying and cannot be evenly dispersed in the DMAC and DMF mixture. It separates into layers after standing, and the upper layer is a transparent clear liquid that contains no or trace amounts of graphene oxide.

[0083] The nanocomposites prepared in the above examples and comparative examples were tested for tensile strength, electrical conductivity, electromagnetic shielding effectiveness, and heat resistance and wear resistance. The results are shown in Table 1.

[0084] Among them, the tensile strength test is carried out in accordance with GB / T 1040.2-2022 "Plastics - Determination of tensile properties - Part 2: Test conditions for molded and extruded plastics", the conductivity test is carried out in accordance with GB / T 3048.2-2007 "Wire and cable electrical properties test methods Part 2: Metallic materials resistivity test", the electromagnetic shielding effectiveness test is carried out in accordance with GB / T30142-2013 "Test method for electromagnetic shielding effectiveness of planar materials", the temperature resistance test is carried out in accordance with GB / T2423.2-2008 "Environmental testing for electric and electronic products Part 2: Test methods Test B: High temperature", and the wear resistance test is carried out in accordance with GB / T 21196.2-2007 "Textiles - Determination of abrasion resistance of fabrics by the Martindale method Part 2: Determination of specimen damage".

[0085] Table 1

[0086]

[0087]

[0088] The data in Table 1 are analyzed as follows:

[0089] Comparative Example 1 (unmodified PMIA fiber)

[0090] Tensile Strength: Example 1 achieved a tensile strength of 255 MPa, while Comparative Example 1 only achieved 55 MPa. This is because the modified graphene in Example 1 reinforces the PMIA nanocomposite, increasing its overall strength. Comparative Example 1, on the other hand, consists solely of PMIA fibers, lacking a reinforcing phase and resulting in lower strength.

[0091] Conductivity: The conductivity of Example 1 is 1700 S·m -1 , Comparative Example 1 is insulating. Modified graphene has good conductivity. The uniformly dispersed modified graphene in Example 1 forms a conductive network in the material, giving the material a certain degree of conductivity. Comparative Example 1 has no conductive components and therefore behaves as an insulator.

[0092] Electromagnetic shielding effectiveness: Example 1 achieved an electromagnetic shielding effectiveness of 48 dB, while Comparative Example 1 achieved 0 dB. The presence of modified graphene helps the material absorb and reflect electromagnetic waves, thereby achieving electromagnetic shielding; the material in Comparative Example 1 lacks this property and therefore has no electromagnetic shielding effect.

[0093] Material decomposition temperature: The decomposition temperature of the material in Example 1 is 500°C, while that in Comparative Example 1 is 400°C. The addition of modified graphene improves the thermal stability of the material, allowing the composite material to decompose at a higher temperature, while the thermal stability of pure PMIA fiber is relatively poor.

[0094] Wear resistance: Example 1 endured over 10,000 abrasion cycles with a mass loss rate of less than 5%, while Comparative Example 1 endured 2,000 abrasion cycles with a mass loss rate of 15%. The presence of modified graphene enhances the material's wear resistance, making it more resistant to wear and reducing mass loss during friction. In contrast, the pure PMIA fiber in Comparative Example 1 exhibited poor wear resistance.

[0095] Comparative Example 2 (Modifier Replaced with SDS)

[0096] Tensile strength: 255 MPa in Example 1 and 150 MPa in Comparative Example 2. Due to the weak bonding and poor dispersibility of SDS and graphene oxide, graphene oxide is not evenly distributed in the material and cannot fully exert its reinforcing effect. Therefore, the tensile strength is lower than that of Example 1.

[0097] Conductivity: Example 1 is 1700 S·m -1 , Comparative Example 2 is 500S·m -1 Poor dispersion makes it difficult for graphene oxide to form an effective conductive network, thereby reducing the electrical conductivity of the material.

[0098] Electromagnetic shielding effectiveness: 48 dB for Example 1 and 20 dB for Comparative Example 2. Poor dispersion affects the absorption and reflection of electromagnetic waves by graphene oxide, resulting in a decrease in electromagnetic shielding effectiveness.

[0099] Material decomposition temperature: 500° C. for Example 1 and 490° C. for Comparative Example 2. Although the use of SDS has a certain impact on the thermal stability of the material, the impact is relatively small, and the material decomposition temperature is slightly reduced.

[0100] Wear resistance: Example 1 had a wear resistance of more than 10,000 times and a mass loss rate of less than 5%, while Comparative Example 2 had a wear resistance of 6,000 times and a mass loss rate of 10%. The uneven dispersion of graphene oxide also reduced the wear resistance of the material.

[0101] Comparative Example 3 (Solvent Replaced with DMAC Only in Step S2)

[0102] Tensile strength: 255 MPa in Example 1 and 200 MPa in Comparative Example 3. DMAC alone may not be as effective as a mixed solvent of DMAC and DMF in dispersing graphene oxide, resulting in less uniform dispersion of graphene oxide in the material, weakened reinforcement effect, and reduced tensile strength.

[0103] Conductivity: Example 1 is 1700 S·m -1 , Comparative Example 3 is 700S·m -1 Poor dispersion affects the formation of the conductive network, and the conductivity decreases accordingly.

[0104] Electromagnetic shielding effectiveness: 48 dB for Example 1 and 30 dB for Comparative Example 3. The uneven dispersion of graphene oxide affects its effect on electromagnetic waves, resulting in a decrease in electromagnetic shielding effectiveness.

[0105] Material decomposition temperature: Example 1 and Comparative Example 3 are both 500°C, indicating that the change of solvent has little effect on the thermal stability of the material.

[0106] Wear resistance: Example 1 has a wear resistance of more than 10,000 times and a mass loss rate of less than 5%, while Comparative Example 3 has a wear resistance of 7,000 times and a mass loss rate of 8%. The dispersibility problem makes the wear resistance of the material inferior to that of Example 1.

[0107] Comparative Example 4 (Solvent Replaced with DMF Only in Step S2)

[0108] Tensile strength: 255 MPa in Example 1 and 180 MPa in Comparative Example 4. Similar to Comparative Example 3, the dispersion effect of DMF alone is significantly inferior to that of the mixed solvent, resulting in uneven dispersion of graphene oxide and lower tensile strength than in Example 1.

[0109] Conductivity: Example 1 is 1700 S·m -1 , Comparative Example 4 is 550S·m -1 Poor dispersion leads to an imperfect conductive network and reduced conductivity.

[0110] Electromagnetic shielding effectiveness: 48 dB for Example 1 and 25 dB for Comparative Example 4. The uneven dispersion of graphene oxide affects the electromagnetic shielding effect.

[0111] Material decomposition temperature: Example 1 and Comparative Example 4 are both 500°C, indicating that the change of solvent has no obvious effect on thermal stability.

[0112] Wear resistance: Example 1 has a wear resistance of more than 10,000 times and a mass loss rate of less than 5%, while Comparative Example 4 has a wear resistance of 6,500 times and a mass loss rate of 8%. Dispersion problems lead to a decrease in the wear resistance of the material.

[0113] Comparison between Example 1 and Comparative Examples 3 and 4 shows that the solvents DMF and DMAC produce a synergistic effect in the system of the present invention.

[0114] Comparative Example 5 (the filter cake was not washed with ethanol in step S2)

[0115] Tensile strength: 255 MPa for Example 1 and 60 MPa for Comparative Example 5. Comparative Example 5 was not washed with ethanol, resulting in high hardness of the dried graphene oxide and difficulty in evenly dispersing it in the DMAC / DMF mixture. Consequently, the graphene oxide failed to effectively reinforce the material, resulting in extremely low tensile strength, close to that of pure PMIA fiber (Comparative Example 1).

[0116] Conductivity: Example 1 is 1700 S·m -1 , Comparative Example 5 is insulating. Graphene oxide has poor dispersibility and cannot form a conductive network, and the material behaves as an insulator.

[0117] Electromagnetic shielding effectiveness: 48 dB for Example 1 and 0 dB for Comparative Example 5. Since graphene oxide is not evenly distributed, it cannot effectively absorb and reflect electromagnetic waves, resulting in no electromagnetic shielding effect.

[0118] Material decomposition temperature: 500° C. for Example 1 and 405° C. for Comparative Example 5. The poor dispersion of graphene oxide affects its effect on improving the thermal stability of the material, and the material decomposition temperature decreases.

[0119] Wear resistance: Example 1 has a wear resistance of more than 10,000 times and a mass loss rate of less than 5%, while Comparative Example 5 has a wear resistance of 3,000 times and a mass loss rate of 16%. The graphene oxide cannot be evenly dispersed, and the material has poor wear resistance.

[0120] Comparative Example 6 (ethanol is replaced by water in step S2)

[0121] Tensile strength: 255 MPa for Example 1 and 60 MPa for Comparative Example 6. Washing with water makes filtration more difficult, and after drying, the graphene oxide is hard and cannot be evenly dispersed, which cannot effectively strengthen the material and has low tensile strength.

[0122] Conductivity: Example 1 is 1700 S·m -1, Comparative Example 6 is insulating. The graphene oxide is unevenly dispersed and cannot form a conductive network, and the material is insulating.

[0123] Electromagnetic shielding effectiveness: 48 dB for Example 1 and 0 dB for Comparative Example 6. Graphene oxide is not evenly distributed and has no electromagnetic shielding effect.

[0124] Material decomposition temperature: 500° C. for Example 1 and 405° C. for Comparative Example 6. Graphene oxide is poorly dispersed, which weakens the effect of improving the thermal stability of the material and reduces the decomposition temperature.

[0125] Wear resistance: Example 1 had a wear resistance of more than 10,000 times and a mass loss rate of less than 5%, while Comparative Example 6 had a wear resistance of 3,000 times and a mass loss rate of 19%. The poor wear resistance of the material was caused by the dispersion problem of graphene oxide.

[0126] In summary, the modified graphene / PMIA nanocomposite material obtained by the process of the embodiment of the present invention exhibits excellent performance in the above-mentioned tensile strength, electrical conductivity, electromagnetic shielding effectiveness, high temperature resistance, wear resistance and other aspects. However, in the comparative example, changes in factors such as modifiers, solvents, and washing processes all lead to varying degrees of decline in material properties, indicating that the beneficial effect of the present invention is the synergistic effect of the above-mentioned multiple factors.

Claims

1. A method for preparing a modified graphene / PMIA nanocomposite material, characterized in that: The steps include: S1, adding a modifier to the aqueous dispersion of graphene oxide, separating the solid and liquid, and drying to obtain modified graphene oxide powder; S2, adding the modified graphene oxide powder obtained in S1 to a solvent and dispersing it until it is uniform, letting it stand, and taking the upper layer of the dispersion; S3, adding a lithium salt to the dispersion obtained in S2 until fully dissolved; the lithium salt is lithium chloride, lithium bromide or lithium nitrate; S4, adding PMIA staple fibers to the dispersion obtained in S3, and heating to dissolve them to prepare a spinning solution; S5. A wet spinning process is used to spin a wet film, and the wet film is heat-treated to remove the solvent to obtain a graphene / PMIA nanocomposite material.

2. The preparation method according to claim 1, characterized in that In step S1, the modifier is PEI or PAM.

3. The preparation method according to claim 1, characterized in that In step S1, after solid-liquid separation, the solid phase is washed with ethanol and then dried.

4. The preparation method according to claim 1, characterized in that In step S1, the amount of the modifier added relative to the graphene oxide is 10%-25%.

5. The preparation method according to claim 1, characterized in that In step S2, the solvent is a mixture of DMAC and DMF, to which a dispersant is added. The dispersant is a high molecular block copolymer containing an amine anchoring group or a medium polarity hyperdispersant.

6. The preparation method according to claim 1, characterized in that In step S3, the amount of lithium chloride added is 60%-75% of the graphene oxide.

7. The preparation method according to claim 1, characterized in that In step S3, the weight of the PMIA staple fibers is 5-12.5 times that of the modified graphene oxide powder.

8. The preparation method according to claim 1, characterized in that In step S5, the heat treatment temperature is 150°C-200°C.

9. The preparation method according to claim 1, characterized in that In step S5, heat treatment is performed in a high-pressure reactor at a pressure of 1-3 MPa.

10. A modified graphene / PMIA nanocomposite material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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