Flexible conductive adhesive based on graphene doping and preparation method thereof

Abstract

The invention relates to the technical field of conductive adhesives, in particular to a graphene doping-based flexible conductive adhesive and a preparation method thereof. The invention overcomes the defects of poor electrical conductivity and poor thermal conductivity of the existing adhesive. The preparation method comprises the following steps: mixing epoxy resin, carboxyl-terminated liquid nitrile rubber and 1, 4-butanediol diglycidyl ether, adding modified epoxy resin, and continuously mixing to obtain a mixed system; adding a nano-alloy into the mixed system, mixing, and carrying out first-stage high-shear dispersion to obtain a primary mixed material; adding a few-layer graphene and silver powder mixture into the primary mixture, stirring, and performing two-stage high-shear dispersion, low-frequency vibration treatment and vacuum defoaming treatment to obtain the flexible conductive adhesive. Wherein the modified epoxy resin is prepared from modified graphene oxide and epoxy resin; the modified graphene oxide is prepared from graphene oxide and a silane coupling agent. The adhesive prepared in the invention has strong electrical conductivity and strong thermal conductivity, and is suitable for bonding optical communication equipment components.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive adhesives, and particularly to a flexible conductive adhesive based on graphene doping and a preparation method thereof. Background Art

[0002] The performance of conductive adhesives is jointly determined by 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 into the matrix to achieve the directional transmission of electrons; their rheological properties determine the applicability of the coating process, and appropriate viscosity and thixotropy can ensure precise coating and uniform distribution. Chemically, polymer matrices such as epoxy resins and acrylic resins form a three-dimensional network structure during the curing process through polymerization reactions or cross-linking reactions, which not only endows the adhesive with adhesion to the surface of the adherend, but also enhances the connection strength through chemical bonding and intermolecular forces. However, existing conductive adhesives have significant defects in practical applications: Firstly, traditional conductive fillers are prone to agglomeration and sedimentation in the matrix, resulting in discontinuous conductive networks, and the interfacial compatibility between the filler and the matrix is poor, restricting the improvement of conductivity and making it difficult to meet the requirements of low-resistance connections for high-frequency communication and high-speed data transmission; Secondly, due to the large interfacial thermal resistance between the filler and the matrix and the lack of an ordered heat conduction path, heat cannot be effectively conducted, and in high-power electronic devices, the overheating problem caused by poor heat dissipation seriously affects the performance and service life of the device.

[0003] Therefore, there is an urgent need to develop a new type of conductive adhesive to achieve the coordinated improvement of conductivity and thermal conductivity by optimizing the filler dispersion technology, enhancing the interfacial bonding force between the filler and the matrix, and designing an efficient heat conduction network, so as to meet the urgent needs of the modern electronic information industry for high-performance connection materials.

[0004] For this purpose, a flexible conductive adhesive based on graphene doping and a preparation method thereof are proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a flexible conductive adhesive based on graphene doping and a preparation method thereof. In the present invention, epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether are mixed, and then modified epoxy resin is added and mixed continuously to obtain a mixed system; nanoalloy is added to the mixed system and mixed, and then high-shear dispersion is carried out in one stage to obtain a preliminary mixture; few-layer graphene and silver powder mixture are added to the preliminary mixture, stirred, and then high-shear dispersion, low-frequency vibration treatment, and vacuum degassing treatment are carried out in the second stage to obtain a flexible conductive adhesive; among them, the modified epoxy resin is prepared from modified graphene oxide and epoxy resin; the modified graphene oxide is prepared from graphene oxide and a silane coupling agent. The adhesive prepared by the present invention has strong conductivity and high thermal conductivity, and is suitable for bonding optical communication equipment components.

[0006] To achieve the above object, the present invention provides the following technical solutions: On the one hand, the present invention provides a preparation method of a flexible conductive adhesive based on graphene doping, which specifically includes the following steps: After mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, add modified epoxy resin and continue to mix to obtain a mixed system; Add nanoalloy, γ-glycidyl ether oxypropyltrimethoxysilane, and fumed silica to the mixed system and perform high-shear dispersion in the first stage to obtain a preliminary mixture; add few-layer graphene, silver powder mixture, curing agent, and accelerator to the preliminary mixture, stir, and then perform high-shear dispersion in the second stage to obtain a secondary mixture; Perform low-frequency vibration treatment and vacuum degassing treatment on the secondary mixture to obtain a flexible conductive adhesive; The modified epoxy resin is prepared from modified graphene oxide and epoxy resin; The modified graphene oxide is prepared from graphene oxide and γ-glycidyl ether oxypropyltrimethoxysilane.

[0007] Preferably, the preparation method of the modified epoxy resin is: Mix epoxy resin and modified graphene oxide, and stir and react at a constant temperature for 2 - 2.5 h to obtain a modified epoxy resin base material.

[0008] Preferably, the preparation method of the modified graphene oxide is: Add monolayer graphene oxide to dimethylformamide for ultrasonic dispersion to obtain a dispersion liquid, then add a modified solution with a mass fraction of 5 - 8% and triethylamine solution to the dispersion liquid, react at a constant temperature for 4 - 6 h, and then wash and dry the reaction product to obtain modified graphene oxide; the modified solution is prepared from γ-glycidyl ether oxypropyltrimethoxysilane and methylformamide.

[0009] Preferably, the preparation method of the preliminary mixture is: Mix epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, add modified epoxy resin and continue to mix to obtain a mixed system; add nanoalloy, γ-glycidyl ether oxypropyltrimethoxysilane, and fumed silica to the mixed system and continue to mix to obtain a mixture, then transfer the mixture to a ceramic three-roll mill for high-shear dispersion in the first stage, set the two-stage grinding gap to 5 - 8 μm and 3 - 5 μm, and the grinding speed to 250 - 300 revolutions per second to grind and obtain the preliminary mixture.

[0010] Preferably, the weight ratio of epoxy resin, modified epoxy resin, and nanoalloy is 15 - 20:10:1 - 1.4.

[0011] Preferably, the method for preparing the secondary mixture is as follows: add few-layer graphene, silver powder mixture, curing agent dicyandiamide, accelerator 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol to the primary mixture, stir and then transfer it to a ceramic three-roll grinder for two-stage high-shear dispersion. Set the two-stage grinding gap to 20-25 μm and 10-15 μm, and set the grinding speed to 200-250 revolutions per second to obtain the secondary mixture by grinding.

[0012] 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.

[0013] Preferably, the low-frequency vibration treatment conditions are as follows: the low-frequency vibration treatment time is 10-15 min; the amplitude is set to 0.3-0.6 mm; the vibration frequency is set to 40-60 Hz.

[0014] 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, nanoalloy, γ-glycidyl etheroxypropyltrimethoxysilane, fumed silica, few-layer graphene, silver powder mixture, curing agent dicyandiamide, accelerator 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the present invention, the epoxy-functionalized graphene prepared from modified single-layer graphene oxide is chemically bonded into the epoxy backbone in the base epoxy resin to form an optimized graphene-modified epoxy prepolymer base, which provides a stable, uniform and easily wettable polymer substrate for all subsequent fillers. At the same time, the nano SAC305 alloy spherical powder is completely deagglomerated under the first-stage high-shear dispersion, effectively improving the nano-scale conduction efficiency. The highly conductive few-layer graphene utilizes its intrinsic transport advantages of high lattice integrity and large lateral size to form a multi-level synergy with the epoxy-functionalized graphene network in the optimized substrate, constructing an efficient electron and phonon conduction pathway. The flaky silver powder and spherical silver powder optimize the filling and overlapping efficiency through particle size differences, forming a large-scale conductive and heat-conductive connected network. At this stage, the nano SAC305 alloy spherical powder fills the voids between the micron-scale silver powders, effectively reducing the electron transition resistance and the interfacial resistance of phonon transmission, and improving the electrical and thermal conductivity of the material.

[0016] 2. In the present invention, epoxy-functionalized graphene is incorporated into the epoxy backbone through chemical bonding, enhancing the toughness and load-bearing capacity of the polymer matrix itself. At the same time, it provides a stable, uniform, and easily wettable polymer substrate for the subsequent introduced fillers, reducing interfacial defects. γ-Glycidoxypropyltrimethoxysilane is used as a coupling agent to promote the strong bonding at the interface between the nano-SAC305 alloy and the resin, reducing the risk of interfacial debonding. The uniform dispersion and fine distribution of highly conductive few-layer graphene and multi-graded silver powder avoid the negative impact on mechanical properties and support the overall strength of the material.

[0017] 3. In the present invention, the staged high-shear dispersion process addresses the challenge that it is difficult to simultaneously optimize the dispersion of fillers with different particle sizes with a single grinding parameter, ensuring the optimal distribution state of multi-scale fillers, forming a continuous and low-impedance electron-phonon transmission path, and supporting high electrical and thermal conductivity. Immediately afterwards, the low-frequency vibration-assisted densification process reduces the particle spacing by inducing the microscopic rearrangement and packing of the dispersed fillers, improving the material density and uniformity, reducing the tunneling resistance, and supporting the overall strength. Finally, the vacuum degassing process removes the bubbles in the material that act as insulators, heat insulators, or stress concentration points, ensuring the continuity and integrity of the conductive and thermal conductive network and the material structure. Through these progressive and collaborative controls of processes from the refined selection of filler particle sizes, the synergistic complementarity of multi-type 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

[0018] Figure 1 It is a bar chart of the tensile shear strength test for Example 1 of the present invention and Comparative Examples 1-3, Comparative Examples 8-11. DETAILED DESCRIPTION OF THE INVENTION

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Please refer to Figure 1 , the present invention provides a flexible conductive adhesive based on graphene doping and its preparation method, and the technical solutions are as follows: Example 1

[0021] Preparation of Modified Epoxy Resin By weight, add 10 parts of bisphenol A epoxy resin E51 and 4 parts of modified graphene oxide into a reaction kettle. Heat the reaction kettle to 100 °C and keep it constant, and continuously stir at a speed of 50 rpm for 2 hours to obtain the modified epoxy resin.

[0022] Preparation of Modified Graphene Oxide By weight, add 100 parts of monolayer graphene oxide (size: 3 μm) into 1000 parts of dimethylformamide, and ultrasonically treat for 1 hour to obtain a dispersion. Subsequently, add 50 parts of γ-glycidoxypropyltrimethoxysilane into 1000 parts of dimethylformamide to obtain a modified solution with a mass fraction of 5%. Dissolve 2 parts of triethylamine in 98 parts of dimethylformamide to prepare a triethylamine catalyst solution with a mass fraction of 2%. Add the dispersion, the modified solution, and the triethylamine catalyst solution into a reaction kettle, and continuously stir and react at 90 °C for 4 hours. After the reaction is completed, the obtained product is washed and purified with ethanol multiple times, and the purified product is vacuum dried at 60 °C for 12 hours to obtain modified graphene oxide.

[0023] Preparation of Premix By weight, add 15 parts 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 into a double-planet power mixer, and then add the modified epoxy resin. Continuously stir at a rotation speed of 1000 rpm and a revolution speed of 20 rpm for 10 min. Subsequently, add 1 part of nanoalloy (nano SAC305 alloy spherical powder, average particle size 30 nm), 1 part of γ-glycidoxypropyltrimethoxysilane, and 0.3 part of fumed silica into the mixer in sequence, and continue to stir for 15 min to obtain a mixture; transfer the mixture to a ceramic three-roll mill for the first-stage high-shear dispersion. Set the grinding gap to 8 μm and 5 μm, and set the grinding speed to 300 revolutions per second, and conduct grinding 2 times.

[0024] Preparation of Secondary Mixture Transfer the primary mixture to a double-planet power mixer. Add 6 parts of few-layer graphene (with 5 layers and a sheet diameter of 10 μm), 45 parts of silver powder mixture, including 30 parts of flaky silver powder (with a sheet diameter of 5 - 10 μm), 15.0 parts of spherical silver powder (with a particle diameter of 1 - 3 μm), 4 parts of curing agent dicyandiamide, 2 parts of accelerator 2-methylimidazole, and 1 part of accelerator 2,4,6-tris(dimethylaminomethyl)phenol into the mixer in sequence. Continue to stir for 30 min under the conditions of a rotation speed of 1000 rpm and a revolution speed of 20 rpm to obtain a mixture; transfer the mixture to a ceramic three-roll grinder for the second-stage high-shear dispersion. First, set the grinding gap to 25 μm and 15 μm, and the grinding speed to 250 revolutions per second, and conduct grinding 2 times to obtain a secondary mixture.

[0025] Preparation of the Adhesive Transfer the secondary mixture to a container equipped with a low-frequency vibration platform. At room temperature, conduct low-frequency vibration treatment on the secondary mixture for 10 min, set the vibration frequency to 40 Hz, and the amplitude to 0.3 mm. After the low-frequency vibration treatment, obtain the vibration-treated material; transfer the vibration-treated material to a vacuum degassing machine for treatment to finally obtain a graphene-doped flexible conductive adhesive.

[0026] The difference between Example 2 and Example 1 is that in the preparation of modified graphene oxide, add a modified solution with a mass fraction of 6.5% to the dispersion liquid and react at a constant temperature for 5 h. In the preparation of modified epoxy resin, after mixing epoxy resin and modified graphene oxide, stir and react at a constant temperature for 2.3 h. In the preparation of the premix, the number of parts of epoxy resin is 17, the number of parts of modified epoxy resin is 10, and the number of parts of nanoalloy is 1.2. In the first-stage high-shear dispersion, the two-stage grinding gap is set to 8 μm and 5 μm, and the grinding speed is set to 270 revolutions per second. In the preparation of the secondary mixture, the two-stage grinding gap for the second-stage high-shear dispersion is set to 20 μm and 10 μm, and the grinding speed is set to 230 revolutions per second. The weight ratio of flaky silver powder to spherical silver powder is 2:1, and the addition amount of spherical silver powder is 10 parts.

[0027] Example 3 is different from Example 1 in that in the preparation of modified graphene oxide, a modified solution with a mass fraction of 8% is added to the dispersion liquid and reacted at a constant temperature for 6 h. In the preparation of modified epoxy resin, after the epoxy resin and the modified graphene oxide are mixed, they are stirred and reacted at a constant temperature for 2.5 h. In the preparation of the primary mixture, the number of parts of epoxy resin is 20 parts, the number of parts of modified epoxy resin is 10 parts, and the number of parts of nanoalloy is 1.4 parts. In the first-stage high-shear dispersion, the two-stage grinding gaps are set to 5 μm and 3 μm, and the grinding speed is set to 300 revolutions per second. In the preparation of the secondary mixture, the two-stage grinding gaps of the second-stage high-shear dispersion are set to 20 μm and 10 μm, and the grinding speed is set to 250 revolutions per second. The weight ratio of flaky silver powder to spherical silver powder is 7:2, and the addition amount of spherical silver powder is 10 parts.

[0028] Example 4 is different from Example 2 in that in the preparation of modified graphene oxide, a modified solution with a mass fraction of 5% is added to the dispersion liquid and reacted at a constant temperature for 4 h. In the preparation of modified epoxy resin, after the epoxy resin and the modified graphene oxide are mixed, they are stirred and reacted at a constant temperature for 2 h. In the preparation of the primary mixture, the number of parts of epoxy resin is 18 parts, the number of parts of modified epoxy resin is 10 parts, and the number of parts of nanoalloy is 1.2 parts. In the first-stage high-shear dispersion, the two-stage grinding gaps are set to 5 μm and 3 μm, and the grinding speed is set to 300 revolutions per second. In the preparation of the secondary mixture, the two-stage grinding gaps of the second-stage high-shear dispersion are set to 20 μm and 10 μm, and the grinding speed is set to 230 revolutions per second. The weight ratio of flaky silver powder to spherical silver powder is 2:1, and the addition amount of spherical silver powder is 10 parts. The low-frequency vibration treatment time is 13 min, the amplitude is 0.5 mm, and the vibration frequency is 50 Hz.

[0029] Example 5 is different from Example 2 in that in the preparation of modified graphene oxide, a modified solution with a mass fraction of 8% is added to the dispersion liquid and reacted at a constant temperature for 6 h. In the preparation of modified epoxy resin, after the epoxy resin and the modified graphene oxide are mixed, they are stirred and reacted at a constant temperature for 2.5 h. In the preparation of the primary mixture, the number of parts of epoxy resin is 20 parts, the number of parts of modified epoxy resin is 10 parts, and the number of parts of nanoalloy is 1.4 parts. In the first-stage high-shear dispersion, the two-stage grinding gaps are set to 8 μm and 5 μm, and the grinding speed is set to 270 revolutions per second. In the preparation of the secondary mixture, the two-stage grinding gaps of the second-stage high-shear dispersion are set to 20 μm and 10 μm, and the grinding speed is set to 230 revolutions per second. The weight ratio of flaky silver powder to spherical silver powder is 7:2, and the addition amount of spherical silver powder is 10 parts. The low-frequency vibration treatment time is 15 min, the amplitude is 0.6 mm, and the vibration frequency is 60 Hz.

[0030] Comparative Example 1 is different from Example 1 only in that: modified single-layer graphene oxide is not added.

[0031] The difference between Comparative Example 2 and Example 1 is only that: the single-layer graphene oxide is not subjected to modification treatment.

[0032] The difference between Comparative Example 3 and Example 1 is only that: when preparing the modified epoxy resin, 10 parts of bisphenol A epoxy resin E51, 4 parts of single-layer graphene oxide, and 2 parts of γ-glycidoxypropyltrimethoxysilane are added to the reaction kettle for reaction to obtain the modified epoxy resin.

[0033] The difference between Comparative Example 4 and Example 1 is only that: no nanoalloy is added.

[0034] The difference between Comparative Example 5 and Example 1 is only that: no few-layer graphene is added.

[0035] The difference between Comparative Example 6 and Example 1 is only that: only flaky silver powder is used in the silver powder mixture.

[0036] The difference between Comparative Example 7 and Example 1 is only that: only spherical silver powder is used in the silver powder mixture.

[0037] The difference between Comparative Example 8 and Example 1 is only that: in the silver powder mixture, there are 10 parts of flaky silver powder and 20 parts of spherical silver powder.

[0038] The difference between Comparative Example 9 and Example 1 is only that: only one high-shear dispersion is carried out. After mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, the modified epoxy resin is added and further mixed to obtain a mixed system; nanoalloy, γ-glycidoxypropyltrimethoxysilane, fumed silica, few-layer graphene, silver powder mixture, curing agent dicyandiamide, accelerator 2-methylimidazole, and 2,4,6-tris(dimethylaminomethyl)phenol are added to the mixed system at one time, and high-shear dispersion is carried out in a ceramic three-roll grinder, and the two-stage grinding gap is set to 25 μm and 15 μm.

[0039] The difference between Comparative Example 10 and Example 1 is only that: only 1 grinding is carried out for both the first-stage high-shear dispersion and the second-stage high-shear dispersion.

[0040] The difference between Comparative Example 11 and Example 1 is only that: no low-frequency vibration treatment is carried out.

[0041] Test Example 1 Test objects: Examples 1-5 and Comparative Examples 1-11.

[0042] Test method: The conductive adhesives of the present invention obtained in each of the above examples are placed in an oven at 140 °C for 3 min. The resistivity of the cured material is tested according to the four-wire method, and the thermal conductivity is tested according to the laser flash method. The final test results are shown in Table 1.

[0043] Table 1 Test Results of Electrical and Thermal Conductivity

[0044] In Comparative Example 1, the modified single-layer graphene oxide was missing, resulting in its inability to form chemical bonds with the base epoxy resin. The optimized internal network structure of the graphene-modified epoxy prepolymer base was not formed, thus unable to effectively reduce the electron transfer resistance and phonon scattering at the graphene-resin interface, hindering the transfer efficiency. In Comparative Example 2, the single-layer graphene oxide was not modified, with poor compatibility with the matrix, forming severe agglomeration and directly blocking the electron and phonon transfer paths. In Comparative Example 3, the preparation of the modified epoxy resin did not undergo stepwise polymerization, affecting the bonding quality between graphene and the epoxy backbone and the network formation efficiency, resulting in a decline in the transfer performance. In Comparative Example 4, the nanoalloy was missing, causing the voids between the micron-sized fillers to be not effectively filled, increasing the interface resistance of electron tunneling and phonon transfer. In Comparative Example 5, the few-layer graphene was missing, lacking a long-range and efficient intrinsic transfer backbone, making the electron and phonon transfer paths inefficient. In Comparative Example 6, only flaky silver powder was used, with insufficient optimization of the filling density, affecting the network continuity. In Comparative Example 7, only spherical silver powder was used, failing to effectively construct a long-range and efficient overlapping conductive and thermal conduction path. In Comparative Example 8, the proportion of the silver powder mixture was unbalanced, reducing the packing density and connectivity and affecting the transfer efficiency. In Comparative Example 9, the one-time mixing and single grinding parameters led to uneven dispersion of the fillers, forming a large number of agglomerations and voids, and the network was discontinuous. In Comparative Example 10, the number of grinding times was reduced, with insufficient dispersion of the fillers and network densification, increasing the transfer resistance. In Comparative Example 11, the low-frequency vibration-assisted densification was missing, the packing of the fillers was not dense, the particle spacing increased, affecting the transfer efficiency.

[0045] The comprehensive analysis of these comparative examples fully demonstrates the effectiveness of this solution in improving the electrical and thermal conductivity. Comparative Examples 1, 2, and 3 directly verify the key role of the chemical bonding of epoxy-functionalized graphene and its construction of an optimized network structure in the stepwise polymerization of the base material. The absence or improper process leads to an increase in the interfacial impedance between graphene and the matrix, hindering electron and phonon transfer. Comparative Examples 4, 5, and 7 highlight the indispensability of nanoalloys and few-layer graphene in the construction of multi-scale networks. They optimize micro-contact and provide high-intrinsic transfer paths 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 a continuous and low-impedance electron and phonon transfer path, jointly solving the problem of poor electrical and thermal conductivity of traditional conductive adhesives.

[0046] Test Example 2 Test objects: Example 1, Comparative Examples 1-3, and Comparative Examples 8-11.

[0047] Test method: Inspection was carried out with reference to the GB / T7124-2008 standard. The tensile shear strength of PC to PC was tested, and the curing condition was to place it in an oven at 140 °C for 3 min. The final test results are shown in Table 2 and Figure 1 as follows.

[0048] Table 2 Test Results of Mechanical Properties

[0049] In Comparative Example 1, the modified single-layer graphene oxide was missing, and the toughness and load-bearing capacity of the polymer matrix could not be chemically enhanced. The interfacial bonding was poor, and the stress could not be effectively transmitted. In Comparative Example 2, the single-layer graphene oxide was unmodified, with poor compatibility with the matrix, forming a large number of aggregates, which served 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 the stepwise polymerization, and the optimized network structure of the polymer matrix was damaged, increasing interfacial defects and affecting toughness and load-bearing capacity. In Comparative Example 8, the proportion of the silver powder mixture was unbalanced, the packing density and uniformity of the silver powder in the matrix decreased, forming micro-defects and affecting the overall strength. In Comparative Example 9, the one-time mixing and single grinding parameters led to uneven dispersion of the filler, forming a large number of aggregates and voids, which served 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, the dispersion of the filler and the densification of the network were insufficient, and the internal defects increased, weakening the mechanical properties. In Comparative Example 11, the low-frequency vibration-assisted densification was missing, the packing of the filler was not dense, and there were residual micro-voids inside the material, reducing the structural integrity.

[0050] The comprehensive analysis of these comparative examples systematically demonstrated the effectiveness of this solution in improving the mechanical properties of the material, especially the shear strength. Comparative Examples 1, 2, and 3 highlighted the decisive role of the modified single-layer graphene oxide and its stepwise polymerization process with the base material in constructing an optimized polymer network and strengthening the interface. The absence or improper process led to weakened interfacial bonding, reduced stress transfer efficiency, and increased internal defects. Comparative Example 8 further emphasized the contribution of the optimized ratio of the multi-graded silver powder to the uniformity and densification of the internal structure of the material. Comparative Examples 9, 10, and 11 revealed the indispensability of key process steps such as staged high-shear dispersion, multiple grinding, and low-frequency vibration-assisted densification for the uniform dispersion of the filler, network densification, and internal defect control. These processes jointly ensured the structural integrity of the material, the uniformity of stress distribution, and the ability to inhibit crack propagation, thus comprehensively improving the strength and toughness of the adhesive and solving the problem of insufficient mechanical properties of traditional adhesives.

[0051] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a flexible conductive adhesive based on graphene doping, characterized in that: Specifically, it includes the following steps: After mixing epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, add modified epoxy resin and continue to mix to obtain a mixed system; Add nanoalloy, γ-glycidyletheroxypropyltrimethoxysilane, and fumed silica to the above mixed system, and then carry out high-shear dispersion in the first stage to obtain a preliminary mixture. Add a mixture of few-layer graphene, silver powder, curing agent, and accelerator to the preliminary mixture, stir, and then carry out high-shear dispersion in the second stage to obtain a secondary mixture; Carry out low-frequency vibration treatment and vacuum degassing treatment on the secondary mixture to obtain the flexible conductive adhesive; 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 γ-glycidyletheroxypropyltrimethoxysilane; 2. The preparation method of a flexible conductive adhesive based on graphene doping according to claim 1, characterized in that: The preparation method of the modified epoxy resin is: mix the epoxy resin and the modified graphene oxide, and stir and react at a constant temperature to obtain the modified epoxy resin; 3. The preparation method of a flexible conductive adhesive based on graphene doping according to claim 1, wherein: The preparation method of the modified graphene oxide is: add monolayer graphene oxide to dimethylformamide and disperse it by ultrasonic to obtain a dispersion liquid. Then add the modified solution and triethylamine solution to the dispersion liquid, react at a constant temperature, and then wash and dry the reaction product to obtain the modified graphene oxide; The modified solution is prepared from γ-glycidyletheroxypropyltrimethoxysilane and the dimethylformamide; 4. The preparation method of a flexible conductive adhesive based on graphene doping according to claim 1, characterized in that: The preparation method of the preliminary mixture is: mix the epoxy resin, carboxyl-terminated liquid nitrile rubber, and 1,4-butanediol diglycidyl ether, add the modified epoxy resin and continue to mix to obtain the mixed system. Add the nanoalloy, γ-glycidyletheroxypropyltrimethoxysilane, and fumed silica to the mixed system and continue to mix to obtain a mixture. Then transfer the mixture to a ceramic three-roll mill for high-shear dispersion in the first stage and grind to obtain the preliminary mixture; 5. The preparation method of a flexible conductive adhesive based on graphene doping according to claim 1, characterized in that: The preparation method of the secondary mixture is: add the few-layer graphene, silver powder mixture, curing agent dicyandiamide, and accelerators 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol to the preliminary mixture, stir, and then transfer it to a ceramic three-roll mill for high-shear dispersion in the second stage and grind to obtain the secondary mixture; 6. The preparation method of a flexible conductive adhesive based on graphene doping according to claim 5, wherein: 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; 7. A flexible conductive adhesive based on graphene doping prepared by the preparation method according to claim 1, characterized in that: 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, nanoalloy, γ-glycidyletheroxypropyltrimethoxysilane, fumed silica, few-layer graphene, silver powder mixture, curing agent dicyandiamide, and accelerators 2-methylimidazole and 2,4,6-tris(dimethylaminomethyl)phenol.

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