A flexible conductive adhesive based on graphene doping and preparation method thereof

Abstract

The present invention relates to the technical field of conductive adhesives, and in particular to a flexible conductive adhesive based on graphene doping and a preparation method thereof. The present invention overcomes the shortcomings of poor electrical conductivity and poor thermal conductivity of existing adhesives. The present invention is prepared by mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, and then adding a modified epoxy resin and continuing to mix to obtain a mixed system; adding nano-alloy to the mixed system and mixing it, and then performing a first-stage high-shear dispersion to obtain a primary mixture; adding a few-layer graphene and a silver powder mixture to the primary mixture and stirring, and then performing a second-stage high-shear dispersion, low-frequency vibration treatment, and vacuum degassing treatment to obtain a flexible conductive adhesive; wherein, the modified epoxy resin is prepared from modified graphene oxide and epoxy resin; and the modified graphene oxide is prepared from graphene oxide and a silane coupling agent. The adhesive prepared by the present invention has strong electrical conductivity and thermal conductivity and is suitable for bonding components of optical communication equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive adhesives, and in particular to a graphene-doped flexible conductive adhesive and a preparation method thereof. Background Art

[0002] The performance of conductive adhesives is determined by both their physical and chemical properties. Physically, conductive adhesives form a continuous conductive network by adding conductive fillers such as silver powder, carbon nanotubes, or graphene to the matrix, enabling directional electron transport. Their rheological properties determine the applicability of the coating process, with appropriate viscosity and thixotropy ensuring precise coating and uniform distribution. Chemically, polymer matrices, such as epoxy resins and acrylic resins, form a three-dimensional network structure through polymerization or cross-linking reactions during the curing process. This not only imparts adhesion to the adherend surface but also enhances connection strength through chemical bonding and intermolecular forces. However, existing conductive adhesives have significant defects in practical applications: First, traditional conductive fillers are prone to agglomeration and sedimentation in the matrix, resulting in a discontinuous conductive network, and the interface compatibility between the filler and the matrix is poor, which limits the improvement of conductivity and makes it difficult to meet the demand for low-resistance connection for high-frequency communication and high-speed data transmission; second, due to the large interface thermal resistance between the filler and the matrix and the lack of an orderly thermal conductive path, heat cannot be effectively conducted. In high-power electronic devices, overheating problems caused by poor heat dissipation seriously affect the performance and service life of the equipment.

[0003] Therefore, there is an urgent need to develop a new type of conductive adhesive that can achieve a synergistic improvement in electrical conductivity and thermal conductivity by optimizing the dispersion technology of the filler, enhancing the interfacial bonding between the filler and the matrix, and designing an efficient thermal conductive network to meet the urgent demand of the modern electronic information industry for high-performance connection materials.

[0004] To this end, a graphene-doped flexible conductive adhesive and a preparation method thereof are proposed. Summary of the Invention

[0005] The present invention aims to provide a graphene-doped flexible conductive adhesive and a method for preparing the same. The method comprises mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, and then adding a modified epoxy resin and continuing to mix to obtain a mixed system; adding a nanoalloy to the mixed system and performing a first-stage high-shear dispersion to obtain a primary mixture; adding a mixture of few-layer graphene and silver powder to the primary mixture, stirring, and then performing a second-stage high-shear dispersion, low-frequency vibration treatment, and vacuum degassing to obtain a flexible conductive adhesive; wherein the modified epoxy resin is prepared from modified graphene oxide and epoxy resin; and the modified graphene oxide is prepared from graphene oxide and a silane coupling agent. The adhesive prepared by the present invention has strong electrical and thermal conductivity and is suitable for bonding components of optical communication equipment.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing a graphene-doped flexible conductive adhesive, which specifically comprises the following steps: mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, and then adding modified epoxy resin and continuing to mix to obtain a mixed system;

[0008] Nano alloy, γ-glycidyloxypropyltrimethoxysilane, and fumed silica are added to the mixed system, followed by a first-stage high shear dispersion to obtain a primary mixture; few-layer graphene, a silver powder mixture, a curing agent, and an accelerator are added to the primary mixture, stirred, and followed by a second-stage high shear dispersion to obtain a secondary mixture;

[0009] The secondary mixture is subjected to low-frequency vibration treatment and vacuum degassing treatment to obtain a flexible conductive adhesive;

[0010] The modified epoxy resin is prepared from modified graphene oxide and epoxy resin;

[0011] The modified graphene oxide is prepared from graphene oxide and γ-glycidyloxypropyltrimethoxysilane.

[0012] Preferably, the preparation method of the modified epoxy resin is: after mixing the epoxy resin and the modified graphene oxide, stirring and reacting at a constant temperature for 2-2.5 hours to obtain the modified epoxy resin base material.

[0013] Preferably, the preparation method of modified graphene oxide is: adding a single layer of graphene oxide to dimethylformamide for ultrasonic dispersion to obtain a dispersion, then adding a modification solution and a triethylamine solution with a mass fraction of 5-8% to the dispersion, reacting at a constant temperature for 4-6 hours, washing and drying the reaction product to obtain modified graphene oxide; the modification solution is prepared by γ-glycidyloxypropyltrimethoxysilane and methylformamide.

[0014] Preferably, the preparation method of the primary mixture is: after mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, adding modified epoxy resin and continuing to mix to obtain a mixed system; adding nano alloy, γ-glycidyl ether oxypropyl trimethoxysilane, and fumed silica to the mixed system and continuing to mix to obtain a mixture, and then transferring the mixture to a ceramic three-roll mill for a first stage of high shear dispersion, setting the two grinding gaps to 5-8 μm and 3-5 μm, and the grinding speed to 250-300 rpm, and grinding to obtain the primary mixture.

[0015] Preferably, the weight ratio of epoxy resin, modified epoxy resin and nano alloy is 15-20:10:1-1.4.

[0016] Preferably, the preparation method of the secondary mixture is: adding few-layer graphene, silver powder mixture, curing agent dicyandiamide, accelerator 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol to the primary mixture, stirring and then transferring to a ceramic three-roll grinder for two-stage high shear dispersion, setting the two-stage grinding gaps to 20-25μm and 10-15μm, and the grinding speed to 200-250 rpm to grind to obtain a secondary mixture.

[0017] Preferably, the silver powder mixture is a mixture of flaky silver powder and spherical silver powder; the weight ratio of flaky silver powder to spherical silver powder is 2-7:1-2.

[0018] Preferably, the low-frequency vibration treatment conditions are: low-frequency vibration treatment time is 10-15 minutes; the amplitude is set to 0.3-0.6 mm; and the vibration frequency is set to 40-60 Hz.

[0019] On the other hand, the present invention provides a flexible conductive adhesive based on graphene doping. The raw materials for preparing the flexible conductive adhesive include: epoxy resin, carboxyl-terminated liquid nitrile rubber, 1,4-butanediol diglycidyl ether, modified epoxy resin, nano alloy, γ-glycidyl ether oxypropyltrimethoxysilane, fumed silica, few-layer graphene, silver powder mixture, curing agent dicyandiamide, accelerator 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. In the present invention, epoxy-functionalized graphene prepared from modified monolayer graphene oxide is chemically bonded into the epoxy backbone of the epoxy resin base, forming an optimized graphene-modified epoxy prepolymer base. This provides a stable, uniform, and easily wettable polymer matrix for all subsequent fillers. Simultaneously, the nano-SAC305 alloy spherical powder is completely deagglomerated during the first stage of high-shear dispersion, effectively improving nanoscale conductivity efficiency. Highly conductive few-layer graphene, leveraging its intrinsic transport advantages of high lattice integrity and large lateral dimensions, forms a multi-level synergy with the epoxy-functionalized graphene network within the optimized matrix, creating efficient electron and phonon conduction pathways. Flake and spherical silver powders optimize filling and overlapping efficiency through particle size differences, forming a large-scale conductive and thermally interconnected network. At this stage, the nano-SAC305 alloy spherical powder fills the gaps between the micron-sized silver powders, effectively reducing the electron transition resistance and the interfacial resistance of phonon transmission, thereby improving the material's electrical and thermal conductivity.

[0022] 2. In the present invention, epoxy-functionalized graphene is chemically bonded into the epoxy backbone, enhancing the toughness and load-bearing capacity of the polymer matrix itself. It also provides a stable, uniform, and easily wettable polymer base for the subsequently introduced filler, reducing interfacial defects. γ-Glycidyloxypropyltrimethoxysilane, used as a coupling agent, promotes a strong bond between the nano-SAC305 alloy and the resin interface, reducing the risk of interfacial debonding. The uniform dispersion and fine distribution of highly conductive few-layer graphene and multi-graded silver powder avoid negative impacts on mechanical properties and support the overall strength of the material.

[0023] 3. In the present invention, the staged high-shear dispersion process addresses the challenge of a single grinding parameter being difficult to simultaneously optimize the dispersion of fillers of different particle sizes, ensuring the optimal distribution of multi-scale fillers, forming a continuous and low-impedance electron-phonon transmission path, and supporting high electrical and thermal conductivity. Next, the low-frequency vibration-assisted densification process reduces the particle spacing by inducing microscopic rearrangement and stacking of the dispersed fillers, thereby improving the density and uniformity of the material, reducing the tunneling resistance and supporting the overall strength. Finally, the vacuum degassing process removes bubbles in the material that serve as insulators, thermal insulators, or stress concentration points, ensuring the continuity and integrity of the electrical and thermal network and material structure. Through these progressive and coordinated control processes from the refined selection of filler particle size, the synergistic combination of multiple types of graphene and metal fillers, to the step-by-step polymerization of the base material, staged high-shear dispersion, and low-frequency vibration-assisted densification, this solution successfully achieves excellent electrical, thermal, and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a bar chart of the tensile shear strength test of Example 1 and Comparative Examples 1-3 and Comparative Examples 8-11 of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] See also Figure 1 The present invention provides a graphene-doped flexible conductive adhesive and a preparation method thereof. The technical solution is as follows:

[0027] Example 1

[0028] Preparation of modified epoxy resin

[0029] 10 parts by weight of bisphenol A epoxy resin E51 and 4 parts of modified graphene oxide were added to a reaction kettle, and the reaction kettle was heated to 100° C. and kept constant, and stirred at 50 rpm for 2 hours to obtain the modified epoxy resin.

[0030] Preparation of modified graphene oxide

[0031] 100 parts by weight of monolayer graphene oxide (3 μm in size) were added to 1000 parts of dimethylformamide and sonicated for 1 hour to obtain a dispersion. Subsequently, 50 parts of γ-glycidyloxypropyltrimethoxysilane were added to 1000 parts of dimethylformamide to obtain a 5% (by weight) modified solution. A 2% (by weight) triethylamine catalyst solution was prepared by dissolving 2 parts of triethylamine in 98 parts of dimethylformamide. The dispersion, modified solution, and triethylamine catalyst solution were added to a reactor and stirred at 90°C for 4 hours. After completion of the reaction, the product was purified by multiple ethanol washes and then vacuum-dried at 60°C for 12 hours to obtain modified graphene oxide.

[0032] Preparation of primary mix

[0033] 15 parts by weight of bisphenol A epoxy resin E51, 6 parts of carboxyl-terminated liquid nitrile rubber (CAS No. 68891-46-3), and 6.5 parts of 1,4-butanediol diglycidyl ether were added to a dual planetary mixer. The modified epoxy resin was then added and stirred for 10 minutes at a rotation speed of 1000 rpm and a revolution speed of 20 rpm. Subsequently, 1 part of nanoalloy (nano-SAC305 alloy spherical powder, average particle size 30 nm), 1 part of γ-glycidyloxypropyltrimethoxysilane, and 0.3 parts of fumed silica were added to the mixer and stirred for 15 minutes to obtain a mixture. The mixture was then transferred to a ceramic three-roll mill for the first stage of high-shear dispersion. The milling gaps were set at 8 μm and 5 μm, and the milling speed was set at 300 rpm for two passes.

[0034] Preparation of secondary mix

[0035] The primary mixture was transferred to a dual planetary power mixer, where 6 parts of few-layer graphene (5 layers, 10 μm flake diameter) and 45 parts of a silver powder mixture (30 parts of flaky silver powder (5-10 μm flake diameter), 15.0 parts of spherical silver powder (1-3 μm particle size), 4 parts of dicyandiamide (curing agent), 2 parts of 2-methylimidazole (accelerator), and 1 part of 2,4,6-tris(dimethylaminomethyl)phenol (accelerator) were added sequentially. Stirring was continued for 30 minutes at a rotation speed of 1000 rpm and a revolution speed of 20 rpm to obtain a mixture. The mixture was then transferred to a ceramic three-roll mill for a second high-shear dispersion stage. Initially, two grinding steps were performed at a grinding speed of 25 rpm and 15 μm with a grinding gap of 250 rpm to obtain a secondary mixture.

[0036] Preparation of adhesive

[0037] The secondary mixture was transferred to a container equipped with a low-frequency vibration platform. The secondary mixture was subjected to low-frequency vibration treatment at room temperature for 10 minutes at a frequency of 40 Hz and an amplitude of 0.3 mm to obtain a vibration-treated material. The vibration-treated material was then transferred to a vacuum degassing machine to obtain a graphene-doped flexible conductive adhesive.

[0038] Example 2 differs from Example 1 in that, in the preparation of modified graphene oxide, a 6.5% mass fraction of the modified solution was added to the dispersion and reacted at a constant temperature for 5 hours. In the preparation of the modified epoxy resin, the epoxy resin and modified graphene oxide were mixed and stirred at a constant temperature for 2.3 hours. In the preparation of the primary mixture, the epoxy resin comprised 17 parts, the modified epoxy resin comprised 10 parts, and the nanoalloy comprised 1.2 parts. In the first stage of high-shear dispersion, the two grinding gaps were set at 8 μm and 5 μm, and the grinding speed was set at 270 rpm. In the preparation of the secondary mixture, the two grinding gaps in the second stage of high-shear dispersion were set at 20 μm and 10 μm, and the grinding speed was set at 230 rpm. The weight ratio of flaky silver powder to spherical silver powder was 2:1, with 10 parts of spherical silver powder added.

[0039] Example 3 differs from Example 1 in that, in the preparation of modified graphene oxide, an 8% mass fraction of the modified solution was added to the dispersion and reacted at a constant temperature for 6 hours. In the preparation of the modified epoxy resin, the epoxy resin and modified graphene oxide were mixed and reacted at a constant temperature with stirring for 2.5 hours. In the preparation of the primary mixture, the epoxy resin comprised 20 parts, the modified epoxy resin comprised 10 parts, and the nanoalloy comprised 1.4 parts. In the first high-shear dispersion stage, the two grinding gaps were set at 5 μm and 3 μm, and the grinding speed was set at 300 rpm. In the preparation of the secondary mixture, the two grinding gaps in the second high-shear dispersion stage were set at 20 μm and 10 μm, and the grinding speed was set at 250 rpm. The weight ratio of flaky silver powder to spherical silver powder was 7:2, with 10 parts of spherical silver powder added.

[0040] Example 4 differs from Example 2 in that, in the preparation of modified graphene oxide, a 5% mass fraction of the modified solution was added to the dispersion and reacted at a constant temperature for 4 hours. In the preparation of the modified epoxy resin, the epoxy resin and modified graphene oxide were mixed and stirred at a constant temperature for 2 hours. In the preparation of the primary mixture, the epoxy resin contained 18 parts, the modified epoxy resin contained 10 parts, and the nanoalloy contained 1.2 parts. In the first high-shear dispersion stage, the two grinding gaps were set at 5 μm and 3 μm, and the grinding speed was set at 300 rpm. In the preparation of the secondary mixture, the two grinding gaps in the second high-shear dispersion stage were set at 20 μm and 10 μm, and the grinding speed was set at 230 rpm. The weight ratio of flaky silver powder to spherical silver powder was 2:1, with 10 parts of spherical silver powder added. The low-frequency vibration treatment lasted 13 minutes, with an amplitude of 0.5 mm and a frequency of 50 Hz.

[0041] Example 5 differs from Example 2 in that, in the preparation of modified graphene oxide, an 8% mass fraction of the modified solution was added to the dispersion and reacted at a constant temperature for 6 hours. In the preparation of the modified epoxy resin, the epoxy resin and modified graphene oxide were mixed and stirred at a constant temperature for 2.5 hours. In the preparation of the primary mixture, the epoxy resin comprised 20 parts, the modified epoxy resin comprised 10 parts, and the nanoalloy comprised 1.4 parts. In the first high-shear dispersion stage, the two grinding gaps were set at 8 μm and 5 μm, and the grinding speed was set at 270 rpm. In the preparation of the secondary mixture, the two grinding gaps in the second high-shear dispersion stage were set at 20 μm and 10 μm, and the grinding speed was set at 230 rpm. The weight ratio of flaky silver powder to spherical silver powder was 7:2, with 10 parts of spherical silver powder added. The low-frequency vibration treatment lasted 15 minutes, with an amplitude of 0.6 mm and a frequency of 60 Hz.

[0042] The only difference between Comparative Example 1 and Example 1 is that no modified monolayer graphene oxide is added.

[0043] The only difference between Comparative Example 2 and Example 1 is that the single-layer graphene oxide is not modified.

[0044] Comparative Example 3 differs from Example 1 only in that when preparing the modified epoxy resin, 10 parts of bisphenol A epoxy resin E51, 4 parts of monolayer graphene oxide, and 2 parts of γ-glycidyloxypropyltrimethoxysilane are added to a reactor for reaction to obtain the modified epoxy resin.

[0045] The only difference between Comparative Example 4 and Example 1 is that no nano alloy is added.

[0046] The only difference between Comparative Example 5 and Example 1 is that the few-layer graphene is not added.

[0047] The only difference between Comparative Example 6 and Example 1 is that only flake silver powder is used in the silver powder mixture.

[0048] The only difference between Comparative Example 7 and Example 1 is that only spherical silver powder is used in the silver powder mixture.

[0049] Comparative Example 8 differs from Example 1 only in that the silver powder mixture contains 10 parts of flaky silver powder and 20 parts of spherical silver powder.

[0050] Comparative Example 9 differs from Example 1 only in that: only one high shear dispersion is performed, and after mixing the epoxy resin, the carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, the modified epoxy resin is added and the mixing is continued to obtain a mixed system; nano alloy, γ-glycidyloxypropyltrimethoxysilane, fumed silica, few-layer graphene, a silver powder mixture, a curing agent dicyandiamide, an accelerator 2-methylimidazole, and 2,4,6-tris(dimethylaminomethyl)phenol are added to the mixed system at one time, and high shear dispersion is performed in a ceramic three-roll mill, and the two grinding gaps are set to 25 μm and 15 μm.

[0051] The only difference between Comparative Example 10 and Example 1 is that both the first-stage high shear dispersion and the second-stage high shear dispersion were ground only once.

[0052] The only difference between Comparative Example 11 and Example 1 is that no low-frequency vibration treatment is performed.

[0053] Test Example 1

[0054] Test objects: Examples 1-5 and Comparative Examples 1-11.

[0055] Testing Method: The conductive adhesives obtained in the above examples were placed in an oven at 140°C for 3 minutes to cure. The cured materials were tested for resistivity using the four-wire method, and for thermal conductivity using the laser flash point method. The final test results are shown in Table 1.

[0056] Table 1 Electrical and thermal conductivity test results

[0057]

[0058] In Comparative Example 1, the modified monolayer graphene oxide is missing, preventing it from chemically bonding with the epoxy resin base. Consequently, the optimized internal network structure of the graphene-modified epoxy prepolymer base fails to form, effectively reducing the electron transmission resistance and phonon scattering at the graphene-resin interface, hindering transmission efficiency. In Comparative Example 2, the monolayer graphene oxide is unmodified, resulting in poor compatibility with the matrix and severe agglomeration, which directly blocks the electron and phonon transmission paths. In Comparative Example 3, the modified epoxy resin is not prepared in a stepwise polymerization process, affecting the bonding quality and network formation efficiency between the graphene and the epoxy backbone, leading to decreased transmission performance. In Comparative Example 4, the nano-alloy is missing, resulting in ineffective filling of the gaps between the micron-sized fillers, increasing the interfacial resistance to electron tunneling and phonon transmission. In Comparative Example 5, the few-layer graphene is missing, lacking a long-range, efficient intrinsic transmission framework, resulting in inefficient electron and phonon transmission paths. In Comparative Example 6, the sole use of flaky silver powder results in insufficient packing density optimization, affecting network continuity. In Comparative Example 7, only spherical silver powder was used, which failed to effectively construct a long-range, efficient, overlapping conductive and thermal conductive path. In Comparative Example 8, the silver powder mixture ratio was unbalanced, which reduced the bulk density and connectivity, affecting the transmission efficiency. In Comparative Example 9, the one-time mixing and single grinding parameters resulted in uneven dispersion of the filler, forming a large number of agglomerates and voids, and a discontinuous network. In Comparative Example 10, the number of grinding times was reduced, the filler dispersion and network densification were insufficient, and the transmission resistance was increased. In Comparative Example 11, low-frequency vibration-assisted densification was missing, the filler stacking was not dense, and the particle spacing increased, affecting the transmission efficiency.

[0059] The comprehensive analysis of these comparative examples fully demonstrates the effectiveness of this solution in improving electrical and thermal conductivity. Comparative Examples 1, 2, and 3 directly verify the chemical bonding of epoxy-functionalized graphene and its key role in constructing an optimized network structure in the step-by-step polymerization of the base material. Its absence or improper process leads to an increase in the interface impedance between graphene and the matrix, and the transmission of electron phonons is hindered. Comparative Examples 4, 5, and 7 highlight the indispensability of nano-alloys and few-layer graphene in the construction of multi-scale networks. They optimize microscopic contacts and provide high intrinsic transmission pathways, respectively. Their absence directly weakens the electrical and thermal conductivity efficiency. Comparative Examples 6 and 8 further emphasize the importance of multi-graded silver powder in optimizing filling and connecting networks. Comparative Examples 9, 10, and 11 systematically demonstrate the decisive influence of process steps such as staged high shear dispersion, multiple grinding, and low-frequency vibration-assisted densification on filler dispersion, network densification, and bubble removal. These processes ensure the formation of continuous and low-impedance electron phonon transmission pathways, which together solve the problem of poor electrical and thermal conductivity of traditional conductive adhesives.

[0060] Test Example 2

[0061] Test objects: Example 1 and Comparative Examples 1-3, Comparative Examples 8-11.

[0062] Test method: Refer to GB / T7124-2008 standard to test the tensile shear strength of PC to PC. The curing condition is to place it in an oven at 140℃ for 3 minutes. The final test results are shown in Table 2 and Figure 1 shown.

[0063] Table 2 Mechanical properties test results

[0064]

[0065] In Comparative Example 1, the modified monolayer of graphene oxide was missing, and the toughness and load-bearing capacity of the polymer matrix were not chemically enhanced, resulting in poor interfacial bonding and ineffective stress transfer. In Comparative Example 2, the monolayer of graphene oxide was unmodified and had poor compatibility with the matrix, forming a large number of agglomerates, which acted as stress concentration points and defect sources, weakening the material's ability to resist damage. In Comparative Example 3, the preparation of the modified epoxy resin did not follow step-by-step polymerization, which damaged the optimized network structure of the polymer matrix, increased interfacial defects, and affected toughness and load-bearing capacity. In Comparative Example 8, the silver powder mixture was unbalanced, and the packing density and uniformity of the silver powder in the matrix decreased, forming microscopic defects and affecting overall strength. In Comparative Example 9, the one-time mixing and single grinding parameters resulted in uneven filler dispersion, forming a large number of agglomerates and voids, which acted as weak points and stress concentration sources, reducing the structural integrity of the material. In Comparative Example 10, the number of grinding times was reduced, resulting in insufficient filler dispersion and network densification, an increase in internal defects, and weakened mechanical properties. In Comparative Example 11, low-frequency vibration-assisted densification is missing, the filler is not densely packed, and microscopic voids remain inside the material, reducing the structural integrity.

[0066] The comprehensive analysis of these comparative examples systematically demonstrates the effectiveness of this solution in improving the mechanical properties of materials, especially shear strength. Comparative Examples 1, 2, and 3 highlight the decisive role of modified monolayer graphene oxide and its step-by-step polymerization process with the base material in constructing an optimized polymer network and strengthening the interface. Its absence or improper process leads to weakened interface bonding, reduced stress transfer efficiency, and increased internal defects. Comparative Example 8 further emphasizes the contribution of the optimized ratio of multi-graded silver powder to the uniformity and density of the internal structure of the material. Comparative Examples 9, 10, and 11 reveal the indispensability of key process steps such as staged high-shear dispersion, multiple grinding, and low-frequency vibration-assisted densification for filler dispersion uniformity, network densification, and internal defect control. These processes together ensure the structural integrity of the material, uniform stress distribution, and the ability to suppress crack propagation, thereby comprehensively improving the strength and toughness of the adhesive and solving the problem of insufficient mechanical properties of traditional adhesives.

[0067] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a graphene-doped flexible conductive adhesive, characterized in that: The specific steps include: After mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, modified epoxy resin is added and mixed continuously to obtain a mixed system; Nano alloy, γ-glycidyloxypropyltrimethoxysilane, and fumed silica are added to the mixed system, followed by a first-stage high-shear dispersion to obtain a primary mixture; few-layer graphene, a silver powder mixture, a curing agent, and an accelerator are added to the primary mixture, stirred, and followed by a second-stage high-shear dispersion to obtain a secondary mixture; the silver powder mixture is a mixture of flaky silver powder and spherical silver powder; the weight ratio of the flaky silver powder to the spherical silver powder is 2-7:1-2; The flexible conductive adhesive is obtained by subjecting the secondary mixture to low-frequency vibration treatment and vacuum degassing treatment; The method for preparing the primary mixture comprises: mixing the epoxy resin, the carboxyl-terminated liquid nitrile rubber, and the 1,4-butanediol diglycidyl ether, adding the modified epoxy resin, and continuing to mix to obtain the mixed system; adding the nano alloy, the γ-glycidyloxypropyltrimethoxysilane, and the fumed silica to the mixed system, and continuing to mix to obtain a mixture; then transferring the mixture to a ceramic three-roll mill for a first stage of high shear dispersion, and grinding to obtain the primary mixture, wherein the two grinding gaps are set to 5-8 μm and 3-5 μm, and the grinding speed is 250-300 rpm; The secondary mixture is prepared by adding the few-layer graphene, the silver powder mixture, the curing agent dicyandiamide, the accelerator 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol to the primary mixture, stirring, and then transferring the mixture to a ceramic three-roll mill for the two-stage high shear dispersion and grinding to obtain the secondary mixture, wherein the two-stage grinding gaps are set to 20-25 μm and 10-15 μm, and the grinding speed is set to 200-250 rpm; The conditions of the low-frequency vibration treatment are as follows: the low-frequency vibration treatment time is 10-15 minutes; the amplitude is set to 0.3-0.6 mm; the vibration frequency is set to 40-60 Hz; The modified epoxy resin is prepared from modified graphene oxide and the epoxy resin; The modified graphene oxide is prepared from graphene oxide and the gamma-glycidyloxypropyltrimethoxysilane.

2. The method for preparing a graphene-doped flexible conductive adhesive according to claim 1, wherein: The preparation method of the modified epoxy resin comprises: mixing the epoxy resin and the modified graphene oxide, stirring and reacting the mixture at a constant temperature to obtain the modified epoxy resin.

3. The method for preparing a graphene-doped flexible conductive adhesive according to claim 1, wherein: The preparation method of the modified graphene oxide comprises: adding a single-layer graphene oxide to dimethylformamide for ultrasonic dispersion to obtain a dispersion liquid, then adding a modified solution and a triethylamine solution to the dispersion liquid, reacting at a constant temperature, washing and drying the reaction product to obtain the modified graphene oxide; The modified solution is prepared from gamma-glycidyloxypropyltrimethoxysilane and dimethylformamide.

4. A graphene-doped flexible conductive adhesive prepared by the preparation method of claim 1, characterized in that: The flexible conductive adhesive is prepared from raw materials including epoxy resin, carboxyl-terminated liquid nitrile rubber, 1,4-butanediol diglycidyl ether, modified epoxy resin, nano alloy, γ-glycidyloxypropyltrimethoxysilane, fumed silica, few-layer graphene, a silver powder mixture, a curing agent of dicyandiamide, and accelerators of 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol.

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