Environment-friendly epoxy resin adhesive and preparation method thereof

Abstract

This invention belongs to the field of adhesive technology, specifically relating to an environmentally friendly epoxy resin adhesive and its preparation method. This invention introduces POSS-graphene and micron-sized spherical silver powder as conductive bridges and network frameworks into a traditional epoxy-micron-scale silver powder conductive adhesive. Both the micron-scale silver powder and graphene exhibit two-dimensional sheet structures, while POSS has auxiliary dispersion and positioning functions, improving the dispersion of graphene and scale silver powder and contributing to the formation of a more complete silver powder-graphene hybrid conductive network. By adding POSS to modify graphene and micron-sized spherical silver powder, the synergistic effect of fillers with different shapes is utilized to optimize the conductive network, solving the technical problems of difficult dispersion of micron-scale silver powder and difficulty in constructing conductive pathways. This further promotes the uniform dispersion of graphene and micron-scale silver powder, reduces the volume resistivity of the conductive adhesive, and enhances conductivity and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to an environmentally friendly epoxy resin adhesive and its preparation method. Background Technology

[0002] With the development of the microelectronics industry, electronic packaging technology is constantly advancing towards miniaturization, precision, and environmental friendliness. Traditional tin-lead soldering technology is increasingly unable to meet the demands of integrated circuit and microelectronic interconnection applications due to its low precision, low line resolution, high soldering temperature, and significant environmental pollution. Adhesives, especially conductive adhesives, can solve the problems faced by tin-lead solders and have attracted widespread attention since their introduction.

[0003] Conductive adhesive is a type of adhesive that possesses both bonding and conductive properties. Compared with traditional tin-lead soldering, conductive adhesive has the following advantages: (1) It can achieve conductive connections with higher line resolution. (2) The construction conditions are relatively mild, avoiding damage to heat-sensitive substrates and high-temperature thermal stress during the soldering process. (3) It does not contain heavy metals such as lead, making it environmentally friendly. (4) As a polymer material, it has better flexibility and fatigue resistance compared to metals. In the electronics industry, conductive adhesive has become an indispensable conductive material, widely used in microelectronic assembly, printed circuit boards, radio frequency antennas, electromagnetic shielding, LED assembly, and other fields.

[0004] Conductive adhesives consist of a resin component and conductive fillers. The resin component includes the main resin, curing agent, various additives, and functional auxiliaries such as accelerators, toughening agents, diluents, dispersants, and coupling agents. It mainly plays a role in bonding and bearing. The conductive fillers are fixed and connected through the curing and cross-linking of the resin component, forming a stable conductive path.

[0005] Conductive fillers serve to connect conductive pathways. Currently, commonly used conductive fillers can be divided into two types: metal-based and carbon-based. Metal-based conductive adhesives mainly include precious metals such as gold (Au) and silver (Ag), and base metals such as copper (Cu) and nickel (Ni). Gold has the best electrical and thermal conductivity, as well as excellent chemical stability, reacting almost unreacted with any chemical substances at room temperature. However, its high price prevents mass production, limiting its use to special applications requiring high oxidation resistance. Silver is the most widely used and longest-established conductive filler. Like gold, silver possesses excellent conductivity and stable physicochemical properties, and it is not easily oxidized in conductive applications. Furthermore, silver is one of the few metals whose oxides can conduct electricity, and its price is relatively low. Therefore, most high-performance conductive adhesives on the market currently use silver as a conductive filler. However, silver is prone to migration in humid environments with DC voltage gradients, leading to a decrease in conductivity. In recent years, due to the continuous rise in precious metal prices, base metals such as copper and their silver-plated materials have also received widespread attention. Copper is inexpensive and does not migrate, but it is prone to oxidation in high temperatures and humid environments. Copper oxides are non-conductive, resulting in poor heat and moisture resistance, limiting its use to products with low conductivity requirements. Copper-based conductive adhesives often use silver-plated copper powder as a filler to prevent oxidation, but silver-plated copper powder-filled conductive adhesives also suffer from aging, leading to increased resistance. Carbon-based fillers such as graphite and carbon black are inexpensive and readily conductive, making them widely used in conductive rubber and conductive inks. However, conductive adhesives made with carbon-based fillers have significantly higher volume resistivity compared to metal-based conductive adhesives, and carbon-based fillers generally suffer from poor dispersion; therefore, they are often used in combination with metal fillers. Summary of the Invention

[0006] This invention proposes an environmentally friendly epoxy resin adhesive and its preparation method. By adding POSS-modified graphene and micron-sized spherical silver powder, the conductive network is optimized through the synergistic effect of fillers of different shapes. This solves the technical problems of difficult dispersion of micron-sized flake silver powder and difficulty in constructing conductive pathways, promotes the uniform dispersion of graphene and micron-sized flake silver powder, reduces the volume resistivity of the conductive adhesive, and enhances conductivity and mechanical properties.

[0007] To achieve the above objectives, the specific technical solution involved in this invention is as follows:

[0008] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0009] (1) A silane coupling agent containing an active group and graphene are dispersed in a solvent, and modified graphene is obtained after the reaction; the mass ratio of the silane coupling agent containing the active group to graphene is (0.1-0.3):1; the active group can undergo nucleophilic substitution reaction with amino groups;

[0010] (2) POSS containing polyamines and modified graphene are dispersed in a solvent and reacted to obtain POSS modified graphene; the molar ratio of POSS containing polyamines to silane coupling agent containing active groups is (0.1-0.3):1.

[0011] (3) Mix the epoxy resin, curing agent, and curing accelerator evenly to obtain the resin matrix;

[0012] (4) Add POSS modified graphene, micron flake silver powder and micron spherical silver powder to the resin matrix, stir evenly, and cure to obtain environmentally friendly epoxy resin adhesive.

[0013] While traditional epoxy resin-micron-sized flake silver powder conductive adhesive is a mainstream material in electronic packaging, the micron-sized flake silver powder is an inert metal and lacks chemical bonding with the organic epoxy resin matrix. Furthermore, compared to spherical silver powder, the flake silver powder has weaker contact interaction, making it more likely to affect the processing flowability of the epoxy resin. Simultaneously, the surface of the silver powder is usually smooth, and its coefficient of thermal expansion differs significantly from that of the resin. Under thermal or mechanical stress, the interface is prone to debonding, becoming the starting point for crack initiation and propagation. This is the main reason for low shear strength, especially the significant strength decay after high temperature or thermal cycling. To achieve high conductivity, the flake silver powder filling amount is usually high. High filler content severely compresses the continuous phase space of the resin matrix, preventing the resin from forming a complete and strong continuous network, further deteriorating the overall mechanical properties of the material and making the adhesive brittle. At the same time, the conductive path depends on point or surface contact between the flake silver powders. This contact is physical and unstable. The volume shrinkage during epoxy resin curing may pull apart the previously contacting flake silver powders, increasing contact resistance.

[0014] To address the aforementioned problems of traditional micron-sized sheet-like silver powder conductive adhesives, this invention employs multi-level chemical modification. By introducing a two-dimensional carbon material with the same sheet-like structure as silver powder, a "rigid-flexible, organic-inorganic synergistic" nano-reinforced / conductive composite filler (POSS-graphene) is constructed. This filler is then introduced into the traditional epoxy-micron-sized sheet-like silver powder system to improve the adhesive's conductivity and mechanical properties.

[0015] Among them, the original graphene sheets, with their extremely high specific surface area and modulus, can effectively hinder the propagation of microcracks in the resin matrix as a two-dimensional nanofiller. It is worth noting that the reason graphene was chosen instead of graphene oxide in this invention is that although graphene oxide has better dispersibility in epoxy resin, its poor conductivity makes it unsuitable as a conductive filler in epoxy conductive adhesives, and it cannot play a role in constructing a conductive network. In contrast, polyamino POSS is a nanoscale rigid cage-like siloxane structure. When it is grafted onto the graphene surface through chemical bonds of a silane coupling agent, it is equivalent to welding numerous three-dimensional rigid nanobumps onto a two-dimensional plane. The remaining amino groups on the surface of POSS-modified graphene can participate in the epoxy curing reaction, anchoring the graphene sheets in the epoxy three-dimensional network through multi-point chemical bonding, greatly enhancing the filler-matrix interfacial bonding force and reducing interfacial slippage. Meanwhile, the surface of micron-sized flake silver powder usually has a certain degree of roughness; while graphene also has a two-dimensional flake structure, and the nano-protrusion structure of POSS on the graphene surface can better interlock with the surface of flake silver powder, thereby improving the bonding strength of the flake silver powder-resin interface, which is difficult to achieve with traditional coupling agents.

[0016] While micron-sized sheet-like silver powder and graphene (two-dimensional sheet-like) are key to constructing surface contacts and the main conductive network framework, effectively reducing the percolation threshold, sheet-like fillers, when tightly packed, are prone to limited contact points due to surface-to-surface parallel contact, or may form isolation in certain areas. Micron-sized spherical silver powder, acting as conductive spheres, can fill the gaps between sheet-like fillers, serving as a connector. It can connect adjacent but not directly contacting graphene or silver sheets, providing additional conductive pathways, making the entire conductive network more compact and three-dimensional, thereby significantly reducing contact resistance and improving overall conductivity stability. Furthermore, single-shaped sheet-like fillers in resins are prone to agglomeration or overlapping due to van der Waals forces or π-π interactions (graphene), affecting dispersion uniformity. The addition of spherical silver powder can act as a physical separator, reducing direct face-to-face aggregation between sheet-like fillers, making the mixed filler system easier to disperse uniformly. From a rheological perspective, spherical fillers generally have less impact on the system viscosity than sheet-like fillers. Adding an appropriate amount of spherical silver powder can increase the filler content without significantly increasing viscosity, thereby improving the printability, coatability, or dispensing performance of conductive adhesives.

[0017] Furthermore, resin shrinks during curing and under stress. Due to its planar structure, the sheet-like filler may oriented or displace under shrinkage stress, leading to the failure of some contact points. Spherical silver powder, being isotropic, can be fine-tuned under shrinkage stress like "ball bearings," forming stable contact points in new positions and enhancing the mechanical stability of the conductive network after curing. Moreover, sheet-like silver powder and graphene are typically expensive; using a small amount of relatively inexpensive micron-sized spherical silver powder as a supplement can effectively reduce raw material costs while improving conductivity, achieving a better performance-price ratio.

[0018] In one embodiment, step (1) specifically involves ultrasonically dispersing a silane coupling agent containing active groups and graphene in a mixed solvent of ethanol and deionized water. After heating and reacting, the resulting product is filtered, washed, and dried to obtain modified graphene. Specifically, the volume ratio of ethanol to deionized water is (0.5-2):1, and can be 0.5:1, 1:1, 1.5:1, or 2:1.

[0019] In one embodiment, the heating reaction temperature is 50-65°C, and the heating reaction time is 1-2.5 h. Specifically, the heating reaction temperature is 55-60°C. A suitable reaction can significantly accelerate the hydrolysis and condensation reaction rates of the silane coupling agent, placing them within the ideal kinetic range, which is beneficial for silane molecules to have sufficient kinetic energy to effectively collide and react with the graphene surface.

[0020] In one embodiment, the active group in step (1) is one or more of the following: carboxyl group, sulfonic acid group, phosphate group, acyl chloride, acid anhydride, isocyanate, sulfonyl chloride, and epoxy group. Specifically, a silane coupling agent with a highly active carboxylic acid group or epoxy group can be selected. Specifically, 3-glycidyl etheroxypropyltrimethoxysilane or 3-glycidyl etheroxypropyltriethoxysilane can be selected.

[0021] The alkyl segments of silane coupling agents containing active groups form the connecting chains between POSS and graphene. These chains possess a degree of flexibility, allowing for better absorption and dissipation of impact energy, thus enhancing the material's toughness. Silane coupling agents with active groups not only connect the inert graphene and POSS groups but, more importantly, promote the uniform dispersion of amino-containing POSS on the graphene surface, preventing POSS accumulation and ensuring the effective isolation and dispersion functions of graphene. This reaction step requires a sufficiently high silane grafting rate to provide ample POSS anchoring sites, but not excessive amounts that would completely encapsulate the graphene in the insulating layer. In other words, a small amount of silane coupling agent forms a monolayer on the graphene surface, chemically bonding with the resin and POSS through its active end groups (such as amino and epoxy groups), improving the interface without affecting direct electron transport between fillers. When the dosage is too high, the excess silane molecules cannot be arranged in an orderly manner at the interface. This will form an excessively thick, disordered multi-molecular layer or even a physical stacking layer on the filler surface. This will not only significantly increase the contact resistance between conductive particles (sheet silver powder, graphene), but also form a weak interfacial bonding layer, which is not conducive to improving conductivity and mechanical properties.

[0022] In one embodiment, the specific process in step (2) is as follows: POSS containing multiple amino groups and modified graphene are dispersed in an organic solvent, heated and stirred to react, and then filtered, washed and dried to obtain POSS modified graphene.

[0023] In one embodiment, the organic solvent in step (2) is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, and tetrahydrofuran.

[0024] In one embodiment, the heating reaction temperature in step (2) is 50-60°C and the reaction time is 5-10h.

[0025] In one embodiment, the POSS containing multiple amino groups in step (2) is a POSS containing 2-8 amino groups. Specifically, it can be one or more of diaminopropyl POSS, diaminophenyl POSS, tetraaminopropyl POSS, tetraaminophenyl POSS, hexaaminopropyl POSS, hexaaminophenyl POSS, octaaminophenyl POSS, and octaaminopropyl POSS.

[0026] In epoxy resin systems, graphene readily aggregates due to π-π stacking, forming stress concentration points. POSS grafting introduces steric hindrance and surface chemical differences, effectively hindering the recombination of graphene sheets and resulting in more uniform dispersion within the resin. A small number of POSS molecules are grafted onto the graphene sheets as discrete nanodots, leaving large exposed or conductive areas on the graphene surface for direct electron transport or tunneling. Excessive POSS molecules form a high-density, nearly continuous insulating layer on the graphene surface, hindering efficient electron transport between the sheet-like silver powders and potentially introducing high-resistance nodes into the conductive pathways. Furthermore, excessive POSS may not only graft onto the graphene surface but also self-aggregate within the system, forming POSS aggregates tens or even hundreds of nanometers in size. These aggregates have poor interfacial bonding with the epoxy matrix, becoming internal stress concentration points and defect origins, easily inducing microcracks.

[0027] In one embodiment, the epoxy resin in step (3) is one or more of the following: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD ​​type epoxy resin, phenolic epoxy resin, and alicyclic epoxy resin.

[0028] In one embodiment, the curing agent in step (3) is one or more of amine, carboxylic acid, and anhydride curing agents. Specifically, one or more of m-phenylenediamine, m-phenylenediamine, polyazelite anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methylnadic anhydride may be selected.

[0029] In one embodiment, the curing accelerator in step (3) is one or more of amines or imidazoles. Specifically, it can be one or more of benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol and its modified forms, 2-ethyl-4-methylimidazole, cyanoethyl-2-ethyl-4-methylimidazole, modified benzyldimethylamine, methylimidazole, diaminodiphenyl sulfone, 2-undecylimidazole, and 2-heptadecanylimidazole. In particular, cyanoethyl-2-ethyl-4-methylimidazole latent curing accelerator can be selected.

[0030] In one embodiment, the mass ratio of epoxy resin, curing agent, and curing accelerator in step (3) is 1:(0.5-1):(0.01-0.03). Further, the mass ratio of epoxy resin, curing agent, and curing accelerator is 1:(0.6-0.9):(0.015-0.025). Insufficient curing agent results in low matrix strength and poor toughness. Unreacted epoxy groups lead to insufficient cohesive strength, making the material prone to cohesive failure under stress. Simultaneously, due to the soft matrix, the "holding power" for the flake silver powder decreases, making the interface prone to failure. Excessive curing agent leads to a denser but potentially more brittle network, and the plasticizing effect reduces strength. Furthermore, excess curing agent may migrate to the interface, forming a weak boundary layer, which is detrimental to improving mechanical properties.

[0031] In one embodiment, in step (4), the total weight of the resin matrix, POSS-modified graphene and silver powder (micron-sized spherical silver powder and micron-sized sheet-like silver powder) is used as the basis, the content of POSS-modified graphene is 0.5-1.5 wt.%, the content of silver powder is 65-75 wt.%, and the balance is the resin matrix.

[0032] In one embodiment, the mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder in step (4) is (1-5):100. Specifically, it can be 1:100, 2:100, 3:100, 4:100, or 5:100. Further, the mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is (2-4):100, as an appropriate amount of micron-sized spherical silver powder can better promote the formation of conductive pathways. In this invention, the size of the micron-sized flake silver powder and the micron-sized spherical silver powder is not particularly limited; any commonly used materials in the art can be used. For example, flake or spherical silver powder with a particle size of 1-10µm can be selected. Specifically, this invention uses flake silver powder with an average particle size of 5µm and spherical silver powder with an average particle size of 1µm. Further, the silver powder can be washed as needed to remove organic matter from its surface and improve conductivity. Further, by stirring, the POSS-modified graphene and silver powder can be fully dispersed in the resin matrix. To facilitate the formation of conductive pathways, a stepwise feeding process can be employed. Specifically, solvents can be added to promote the dispersion of components and the stirring process. Specifically, micron-sized spherical silver powder and micron-sized flake silver powder can be added first, stirred evenly, and then POSS-modified graphene can be added, followed by further stirring to obtain a mixed resin. In resins with relatively low viscosity, the early addition of micron-sized spherical and flake silver powder ensures sufficient wetting and relatively uniform distribution of the silver powder within the resin, laying the foundation for constructing a conductive framework. The subsequently added POSS-modified graphene, due to space competition, tends to distribute more readily on the surface of the already formed silver powder or in the gaps between silver powder clusters, better fulfilling its role as a conductive bridge and interface enhancer. This directly improves the silver powder-resin interface and bridges adjacent silver powders, protecting the silver powder from excessive agglomeration and enhancing the mechanical and conductive properties of the conductive adhesive. Specifically, the POSS-modified graphene content is 0.8-1.4 wt.%, and the silver powder content is 68-70 wt.%. An appropriate amount of silver powder satisfies the need to construct conductive pathways while avoiding agglomeration due to excessive silver powder. An appropriate amount of POSS-modified graphene can effectively disperse between the silver powder particles, acting as a highly efficient conductive bridge connecting parts not directly contacted by the silver powder, significantly reducing contact resistance and causing a rapid decrease in resistivity. However, excessive use of POSS-modified graphene itself is prone to agglomeration and physically blocks silver powder-to-silver powder contact, introducing high-resistance nodes into the conductive pathway, which is detrimental to product performance.

[0033] In one embodiment, the curing temperature in step (4) is 145-155°C and the curing time is 2-3 hours.

[0034] On the other hand, this invention also provides an environmentally friendly epoxy resin adhesive prepared using the above method. Traditional epoxy-flake silver powder conductive adhesives rely on physical contact between flake silver powders to form conductive pathways. This invention introduces POSS-graphene as a conductive bridge and network framework: graphene itself is an excellent conductor. When flake silver powders fail to form perfect contact due to resin shrinkage or uneven arrangement, the conductive graphene flakes dispersed in the gaps can connect adjacent flake silver powders, providing additional electron tunneling or conduction paths and reducing contact resistance. POSS has an auxiliary dispersion and positioning effect, improving the dispersion of graphene and allowing it to be distributed in the gaps between flake silver powders in a more efficient bridging manner, rather than agglomerating into isolated islands. This helps to form a more complete flake silver powder-graphene hybrid conductive network. More importantly, through the chemical anchoring effect of POSS, the bond between graphene and epoxy resin is stronger, and it is less prone to detachment from the matrix during curing shrinkage and thermal cycling, thereby maintaining the long-term stability of the conductive pathway and indirectly improving reliable conductivity. Meanwhile, the addition of rigid POSS-graphene alters the rheological properties of the resin system, affecting the sedimentation and arrangement of flake silver powder before curing, promoting denser stacking of flake silver powder, and facilitating the formation of a stable conductive network. Micron-sized spherical silver powder, acting as conductive spheres, fills the gaps between the flake fillers, serving as a connector. It connects adjacent but not directly contacting graphene or silver sheets, providing additional conductive pathways, making the entire conductive network more compact and three-dimensional, thereby significantly reducing contact resistance and improving overall conductive stability.

[0035] Beneficial effects:

[0036] (1) The two-step chemical method of “silane coupling agent → POSS” was used to achieve precise customization and functional enhancement of the surface properties of graphene. The interfacial bonding strength of chemical bonding is much higher than that of physical adsorption or simple coupling agent treatment, which solves the problem of difficult dispersion of micron-sized silver powder in epoxy resin and greatly improves the ability of micron-sized silver powder to construct conductive pathways.

[0037] (2) This invention introduces POSS-graphene as a conductive bridge and network framework into the traditional epoxy-micron-scale silver powder conductive adhesive. Both micron-scale silver powder and graphene exhibit two-dimensional sheet structures, and POSS has auxiliary dispersion and positioning functions, which improves the dispersion of graphene and sheet-scale silver powder, and helps to form a more complete silver powder-graphene hybrid conductive network. More importantly, through the chemical anchoring effect of POSS, the bonding between graphene and epoxy resin is stronger, and it is not easy to debond from the matrix during curing shrinkage and thermal cycling, thereby maintaining the long-term stability of the conductive path and indirectly improving reliable conductivity.

[0038] (3) Micron-sized spherical silver powder, as conductive spheres, can fill the gaps between sheet-like fillers, playing a connecting role. It can connect adjacent but not directly contacting graphene sheets or silver sheets, providing additional conductive paths, making the entire conductive network more compact and three-dimensional, thereby significantly reducing contact resistance and improving overall conductive stability. Detailed Implementation

[0039] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention are described in detail below with reference to examples. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise specified, the types of raw materials and processes used in the following embodiments are the same.

[0040] Performance testing: The tensile shear properties (refer to GB7124-86) and resistivity (refer to ASTM D257-91) of the environmentally friendly epoxy resin adhesives prepared in the following examples and comparative examples were tested respectively.

[0041] Example 1

[0042] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0043] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 50°C for 2.5 h, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.1:1.

[0044] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 50°C for 10 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.1:1.

[0045] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.75:0.014.

[0046] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 145℃ for 3 hours to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1.1 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 70.5 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 4:100. The tensile shear strength is 12.2 MPa and the volume resistivity is 2.1 × 10⁻⁶. -4 Ω·cm.

[0047] Example 2

[0048] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0049] (1) The silane coupling agent 3-glycidyl etheroxypropyltriethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 65°C for 1 h, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.3:1.

[0050] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 60°C for 5 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.3:1.

[0051] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.9:0.023.

[0052] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 155℃ for 2 hours to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 0.5 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 67 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 1:100. The tensile shear strength is 14.2 MPa and the volume resistivity is 4.8 × 10⁻⁶. -4 Ω·cm.

[0053] Example 3

[0054] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0055] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.2:1.

[0056] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 55°C for 7 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.23:1.

[0057] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0058] (4) After adding POSS-modified graphene to the resin matrix and stirring evenly, silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is added and stirred evenly. The mixture is then cured at 150℃ for 2.5 hours to obtain an environmentally friendly epoxy resin adhesive. Based on the total weight of the resin matrix, POSS-modified graphene, and silver powder, the POSS-modified graphene content is 1.3 wt.%, the silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) content is 69 wt.%, and the remainder is the resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.5:100. The tensile shear strength is 12.9 MPa, and the volume resistivity is 4.6 × 10⁻⁶. -4 Ω·cm.

[0059] Example 4

[0060] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0061] (1) The silane coupling agent 3-glycidyl etheroxypropyltriethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 52°C for 1.3 h, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.12:1.

[0062] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 50°C for 9 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.12:1.

[0063] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.75:0.023.

[0064] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 145℃ for 2 hours to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 67.5 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 1.8:100. The tensile shear strength is 14.8 MPa and the volume resistivity is 5.2 × 10⁻⁶. -4 Ω·cm.

[0065] Example 5

[0066] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0067] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.2:1.

[0068] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 55°C for 7 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.23:1.

[0069] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0070] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 150℃ for 2.5h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1.5wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 69wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.5:100. The tensile shear strength is 13.4MPa and the volume resistivity is 4.9×10⁻⁶. -4 Ω·cm.

[0071] Example 6

[0072] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0073] (1) The silane coupling agent 3-glycidyl etheroxypropyltriethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 54°C for 2.2 h, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.17:1.

[0074] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 52°C for 8 hours, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.15:1.

[0075] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0076] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 148℃ for 2.3h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 0.75wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 69.5wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.2:100. The tensile shear strength is 12.6MPa and the volume resistivity is 2.5×10⁻⁶. -4 Ω·cm.

[0077] Example 7

[0078] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0079] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.2:1.

[0080] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 55°C for 7 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.23:1.

[0081] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0082] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 150℃ for 2.5h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1.3 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 69 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 5:100. The tensile shear strength is 13.3 MPa and the volume resistivity is 3.1 × 10⁻⁶. -4 Ω·cm.

[0083] Example 8

[0084] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0085] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 58°C for 1.6 h, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.25:1.

[0086] (2) POSS containing multiple amino groups (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 58°C for 6 hours, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing multiple amino groups to silane coupling agent containing active groups was 0.25:1.

[0087] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride, and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent, and curing accelerator is 1:0.88:0.021.

[0088] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 152℃ for 2.8h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 0.9 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 68 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 3.4:100. The tensile shear strength is 13.0 MPa and the volume resistivity is 3.2 × 10⁻⁶. -4 Ω·cm.

[0089] Example 9

[0090] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0091] (1) The silane coupling agent 3-glycidyl etheroxypropyltriethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 57°C for 1.9 h, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.22:1.

[0092] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 57°C for 7.5 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.16:1.

[0093] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride, and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent, and curing accelerator is 1:0.78:0.02.

[0094] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 148℃ for 2.6h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 0.7 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 68.5 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 3:100. The tensile shear strength is 13.4 MPa and the volume resistivity is 3.4 × 10⁻⁶. -4 Ω·cm.

[0095] Example 10

[0096] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0097] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.2:1.

[0098] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 55°C for 7 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.23:1.

[0099] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0100] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 150℃ for 2.5h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1.3 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 69 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.5:100. The tensile shear strength is 14.7 MPa and the volume resistivity is 2.3 × 10⁻⁶. -4 Ω·cm.

[0101] Comparative Example 1

[0102] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0103] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.6:1.

[0104] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 55°C for 7 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.23:1.

[0105] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0106] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 150℃ for 2.5h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1.3 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 69 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.5:100. The tensile shear strength is 11.1 MPa and the volume resistivity is 6.6 × 10⁻⁶. -4 Ω·cm.

[0107] Comparative Example 2

[0108] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0109] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.2:1.

[0110] (2) E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride, and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium are mixed evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent, and curing accelerator is 1:0.8:0.018.

[0111] (3) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add modified graphene and stir evenly. Cure at 150℃ for 2.5h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, modified graphene and silver powder, the modified graphene content is 1.3wt.%, the silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) content is 69wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.5:100. The tensile shear strength is 9.5MPa and the volume resistivity is 7.7×10⁻⁶. -4 Ω·cm.

[0112] Comparative Example 3

[0113] A method for preparing an environmentally friendly epoxy resin adhesive includes the following steps:

[0114] (1) The silane coupling agent 3-glycidyl etheroxypropyltrimethoxysilane containing active groups and graphene were ultrasonically dispersed in a mixed solvent of ethanol and deionized water (volume ratio of 1:1). After heating and reacting at 60°C for 2 hours, the modified graphene was obtained by filtration, washing and drying. The mass ratio of the silane coupling agent containing active groups to graphene was 0.2:1.

[0115] (2) POSS containing polyamino group (octaaminophenyl POSS) and modified graphene were dispersed in tetrahydrofuran, heated and stirred at 55°C for 7 h, and then filtered, washed and dried to obtain POSS modified graphene; the molar ratio of POSS containing polyamino group to silane coupling agent containing active group was 0.6:1.

[0116] (3) Mix E51 epoxy resin, curing agent methyl hexahydrophthalic anhydride and curing accelerator cyanoethyl-2-ethyl-4-methylimidazolium evenly to obtain a resin matrix; the mass ratio of epoxy resin, curing agent and curing accelerator is 1:0.8:0.018.

[0117] (4) Add silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) to the resin matrix and stir evenly. Then add POSS-modified graphene and stir evenly. Cure at 150℃ for 2.5h to obtain environmentally friendly epoxy resin adhesive. Based on the total weight of resin matrix, POSS-modified graphene and silver powder, the content of POSS-modified graphene is 1.3 wt.%, the content of silver powder (micron-sized flake silver powder and micron-sized spherical silver powder) is 69 wt.%, and the remainder is resin matrix. The mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is 2.5:100. The tensile shear strength is 10.7 MPa and the volume resistivity is 7.1 × 10⁻⁶. -4 Ω·cm.

[0118] As can be seen from the above embodiments and comparative examples, this invention achieves precise customization and functional enhancement of graphene surface properties through a two-step chemical method of "silane coupling agent → POSS," solving the problem of difficult dispersion of micron-sized flake silver powder in epoxy resin and greatly improving the ability of micron-sized flake silver powder to construct conductive pathways. Both micron-sized flake silver powder and graphene exhibit two-dimensional flake structures, and POSS has an auxiliary dispersion and positioning effect, improving the dispersion of graphene and flake silver powder. This allows graphene to be distributed in the gaps between the flake silver powder in a more efficient bridging manner, contributing to the formation of a more complete silver powder-graphene hybrid conductive network. Through the chemical anchoring effect of POSS, the bond between graphene and epoxy resin is stronger, maintaining the long-term stability of the conductive pathway and indirectly improving reliable conductivity. The micron-sized spherical silver powder, acting as conductive spheres, can fill the gaps between the flake fillers, serving a connecting role. It can connect adjacent but not directly contacting graphene or silver sheets, providing additional conductive pathways, making the entire conductive network more compact and three-dimensional, thereby significantly reducing contact resistance and improving overall conductive stability.

[0119] In this invention, POSS-graphene is not used as the main conductive filler, but primarily serves to promote the dispersion of silver powder and construct conductive pathways. Therefore, the amount of non-conductive silane coupling agent and POSS significantly affects the performance of the epoxy resin. Specifically, compared to Example 10, the amount of silane coupling agent containing active groups in Comparative Example 1 was excessive, resulting in a certain degree of reduction in both conductivity and mechanical properties. This indicates that this reaction step requires a small amount of silane coupling agent to form a monolayer on the graphene surface, which chemically bonds with the resin and POSS through its active end groups, improving the interface without affecting the direct electron transport between fillers. When the amount is excessive, the excess silane molecules cannot all be arranged in an orderly manner at the interface, forming an excessively thick, disordered multilayer or even a physically stacked layer on the filler surface. This not only significantly increases the contact resistance between conductive particles (silver powder, graphene) but also forms a weak interfacial bonding layer, which is detrimental to improving conductivity and mechanical properties.

[0120] Compared to Example 10, Comparative Example 2 did not add POSS containing polyamines, making the graphene prone to stacking, which is detrimental to the construction of conductive pathways and enhanced networks. In Comparative Example 3, the amount of POSS containing polyamines was excessive. Excessive POSS molecules formed a high-density, nearly continuous insulating layer on the graphene surface, hindering efficient electron transfer between silver powders and potentially introducing high-resistance nodes into the conductive pathways. Furthermore, the excessive POSS not only grafted onto the graphene surface but also self-aggregated within the system, forming POSS aggregates tens or even hundreds of nanometers in size. These aggregates have poor interfacial bonding with the epoxy matrix, becoming internal stress concentration points and defect origins, easily inducing microcracks and leading to performance degradation.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an environmentally friendly epoxy resin adhesive, characterized in that, Includes the following steps: (1) A silane coupling agent containing an active group and graphene are dispersed in a solvent, and modified graphene is obtained after the reaction; the mass ratio of the silane coupling agent containing the active group to graphene is (0.1-0.3):1; the active group can undergo nucleophilic substitution reaction with amino groups; (2) POSS containing polyamines and modified graphene are dispersed in a solvent and reacted to obtain POSS modified graphene; the molar ratio of POSS containing polyamines to silane coupling agent containing active groups is (0.1-0.3):

1. (3) Mix the epoxy resin, curing agent, and curing accelerator evenly to obtain the resin matrix; (4) Add POSS modified graphene, micron flake silver powder and micron spherical silver powder to the resin matrix, stir evenly, and cure to obtain environmentally friendly epoxy resin adhesive.

2. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 1, characterized in that, In step (1), the solvent is a mixture of ethanol and deionized water.

3. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 1, characterized in that, The specific process of step (2) is as follows: POSS containing multiple amino groups and modified graphene are dispersed in an organic solvent, heated and stirred to react, and then filtered, washed and dried to obtain POSS modified graphene.

4. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 3, characterized in that, The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, and tetrahydrofuran.

5. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 3, characterized in that, The reaction temperature is 50-60℃, and the reaction time is 5-10h.

6. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 1, characterized in that, In step (2), the polyamino POSS is one or more of the following: diaminopropyl POSS, diaminophenyl POSS, tetraaminopropyl POSS, tetraaminophenyl POSS, hexaaminopropyl POSS, hexaaminophenyl POSS, octaaminopropyl POSS, and octaaminophenyl POSS.

7. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 1, characterized in that, In step (3), the curing agent is one or more of the following: m-phenylenediamine, m-phenylenediamine, polyazelite anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methylnadic anhydride.

8. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 1, characterized in that, In step (3), the curing accelerator is one or more of amines or imidazoles.

9. The method for preparing an environmentally friendly epoxy resin adhesive as described in claim 1, characterized in that, In step (4), the mass ratio of micron-sized spherical silver powder to micron-sized flake silver powder is (1-5):

100.

10. An environmentally friendly epoxy resin adhesive, characterized in that, It is prepared by the method of any one of claims 1-9 for an environmentally friendly epoxy resin adhesive.