Two-component epoxy adhesive and preparation method thereof

Abstract

The application relates to a two-component epoxy adhesive and a preparation method thereof. The preparation raw materials comprise an A component and a B component. The A component comprises the following components in parts by weight: an epoxy resin matrix 40-80 parts, a modified epoxy resin 30-70 parts, calcium carbonate 10-30 parts, a silane coupling agent 2-5 parts, fumed silica 5-10 parts and a reactive toughening diluent 5-20 parts. The B component comprises the following components in parts by weight: a modified polyamide resin 30-60 parts, a polyether amine curing agent 10-30 parts, calcium carbonate 10-30 parts and fumed silica 5-10 parts. The modified epoxy resin is an epoxy resin containing a cage polysilsesquioxane structure. The modified polyamide resin is a cardanol-modified polyamide resin containing an amine end group. The two-component epoxy adhesive is unexpectedly obtained after mixed curing of the A component and the B component, and has high shear strength, high elongation at break and excellent high-low temperature alternating performance.

Description

Technical Field

[0001] This application relates to the field of adhesive technology, and in particular to a two-component epoxy adhesive and its preparation method. Background Technology

[0002] Epoxy adhesives are widely used in microelectronics, automotive electronics, new energy, and optical devices due to their excellent mechanical properties, chemical resistance, high temperature resistance, and ability to bond to a variety of substrates. Their advantages are particularly pronounced in applications requiring high-temperature reflow soldering, wide temperature ranges, and high dimensional stability.

[0003] However, traditional pure epoxy structural adhesives have significant drawbacks: the cured product is brittle, has poor impact resistance, and insufficient toughness and fatigue resistance. They are prone to cracking under mechanical impact or thermal cycling stress, limiting their use in dynamic loads or high-reliability scenarios.

[0004] To address the brittleness issue of epoxy adhesives, the industry has developed hybrid adhesives, such as blends of epoxy resin with flexible resins like polyurethane and other resins. These hybrid adhesives maintain a certain level of strength while significantly improving toughness and impact resistance. However, hybrid adhesives also have drawbacks: the curing behavior of different resin matrices varies greatly, making phase separation prone to occur, affecting the uniformity and reliability of the adhesive layer; moreover, their upper limits of mechanical properties are usually lower than those of pure epoxy systems, making it difficult to meet the requirements of high-strength bonding.

[0005] Therefore, how to effectively improve the toughness, impact resistance and high and low temperature alternation performance of epoxy adhesives while maintaining their high strength, and at the same time avoid the phase separation problem common in hybrid adhesives, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to effectively improve the toughness, impact resistance and high and low temperature alternation resistance of epoxy adhesives, this application provides a two-component epoxy adhesive and its preparation method.

[0007] In a first aspect, this application provides a two-component epoxy adhesive, employing the following technical solution: A two-component epoxy adhesive comprises component A and component B. Component A comprises the following components in parts by weight: 40-80 parts epoxy resin matrix, 30-70 parts modified epoxy resin, 10-30 parts calcium carbonate, 2-5 parts silane coupling agent, 5-10 parts fumed silica, and 5-20 parts reactive toughening diluent. Component B comprises the following components in parts by weight: 30-60 parts modified polyamide resin, 10-30 parts polyetheramine curing agent, 10-30 parts calcium carbonate, and 5-10 parts fumed silica. The modified epoxy resin is an epoxy resin containing a cage-like polysilsesquioxane structure, and the modified polyamide resin is a cashew nut phenol-modified polyamide resin containing terminal amine groups.

[0008] The inventors discovered that through the synergistic effect between the cage-type polysilsesquioxane (POSS) modified epoxy resin in component A and the cashew phenol modified polyamide resin in component B, the two-component epoxy adhesive, after mixing and curing, can simultaneously possess high shear strength, high elongation at break, and excellent resistance to high and low temperature alternating current. Analysis suggests this may be due to: The POSS-modified epoxy resin in component A contains a cage-like polysilsesquioxane structure, whose high-bond-energy Si-O-Si cage-like skeleton exhibits excellent thermal stability and can be covalently embedded in the epoxy molecular chain. During curing, the POSS nanocages are locked at the cross-linking network nodes, forming rigid physical cross-linking points that maintain their shape and modulus at high temperatures, effectively restricting the thermal motion of the molecular chains and endowing the network with good dimensional stability and high-temperature load-bearing capacity. Simultaneously, some of the silanol groups retained on the surface of the POSS cages can undergo condensation or strong hydrogen bonding with the hydroxyl groups or oxides on the surface of the substrate (metal, ceramic, semiconductor packaging materials), introducing nanoscale multi-point chemical anchoring at the interface and significantly improving peel resistance.

[0009] The cashew phenol-modified polyamide resin in component B possesses long alkyl side chains of cashew phenol (derived from natural cashew nut shell liquid), which combine flexibility and hydrophobicity. These chains are permanently suspended on the polyamide molecular chain through a condensation reaction. After curing, these flexible side chains absorb and dissipate energy through conformational adjustment under external impact, inducing microcracks and preventing their propagation into macroscopic damage. They also maintain chain segment mobility at low temperatures, avoiding brittle fracture. Furthermore, the hydrophobicity of the long cashew phenol chains causes them to accumulate at the adhesive-substrate interface before curing, improving wetting and spreading. After curing, they form a flexible transition layer that buffers curing shrinkage stress and thermal stress, preventing interfacial debonding.

[0010] POSS-modified epoxy resin and cashew phenol-modified polyamide resin are co-used in the same two-component system. They are covalently linked through an epoxy-amine curing reaction, forming a microphase topology of alternating "rigid nodes and flexible side chains" in the cross-linked network. The rigid nodes of POSS bear loads and resist high-temperature creep; the flexible side chains of cashew phenol absorb impacts and buffer thermal stress. The two are interdependent at the molecular level, avoiding phase separation or interfacial debonding common in traditional physical blends. At the interface, the polysilanol rigid anchors of POSS and the flexible buffer layer of cashew phenol work synergistically, balancing chemical bond strength and internal stress release. This unexpectedly achieves a balance between high strength and high toughness, as well as excellent resistance to alternating high and low temperatures, over a wide temperature range, which is impossible to obtain simultaneously in traditional single or simple blend systems.

[0011] In one specific implementation scheme, the modification preparation steps of the modified epoxy resin are as follows: S1-1. Dissolve KH-560 in an organic solvent, add water and an acidic catalyst, adjust the pH to 3-4, and carry out a hydrolysis reaction to obtain a hydrolysate containing silanol groups. S2-1. The hydrolysate containing silanol groups obtained in step S1-1 is heated to 60-80°C and polycondensation reaction is continued to form a cage-type polysilsesquioxane prepolymer containing epoxy groups. S3-1. The cage-type polysilsesquioxane prepolymer containing epoxy groups obtained in step S2-1 is mixed with epoxy resin, and then post-treated to obtain the modified epoxy resin.

[0012] The modified epoxy resin prepared by the above steps has cage-like polysilsesquioxanes chemically bonded to the epoxy resin molecular chain to form a uniformly dispersed rigid nanoframework. After curing, it can significantly improve the high-temperature dimensional stability and creep resistance of the cross-linked network. At the same time, the silanol groups retained on the surface of the POSS cage can form multi-point chemical anchoring with the substrate surface, enhancing the interfacial bonding force.

[0013] In one specific feasible implementation, the modification preparation steps of the modified polyamide resin are as follows: The modified polyamide resin is obtained by melt polycondensation reaction of dimer acid, diethylenetriamine, and cashew phenol, followed by post-treatment.

[0014] The modified polyamide resin prepared by the above steps has long alkyl side chains of cashew phenol introduced into its molecular chain and retains the terminal amine structure, thus possessing both the toughening ability of flexible chain segments and the curing activity of reacting with epoxy groups. At the same time, the hydrophobicity of the long alkyl side chains allows them to spontaneously accumulate at the interface between the adhesive layer and the substrate before the adhesive cures, improving wetting and forming a flexible transition layer.

[0015] In one specific implementation, in the modification step of the modified polyamide resin, the mass ratio of dimer acid, diethylenetriamine, and cashew phenol is 100:(27-45):(10-42).

[0016] By controlling the raw materials within the above-mentioned mass ratio, it is possible to ensure that cashew phenol is introduced into the polyamide molecular chain in an appropriate proportion. This not only provides the resin with sufficient long alkyl flexible side chains to improve toughness and interfacial wettability, but also avoids excessive cashew phenol from hindering the polycondensation reaction or reducing the content of terminal amine groups. As a result, the amine value of the modified polyamide resin is kept stable in the range of 200-250 mgKOH / g, maintaining suitable reactivity and crosslinking density with the epoxy groups in component A, thus balancing curing speed and mechanical properties.

[0017] In one specific implementation, the epoxy resin matrix comprises bisphenol A type epoxy resin and bisphenol F type epoxy resin; more preferably, the mass ratio of the bisphenol A type epoxy resin and the bisphenol F type epoxy resin is 1:(0.8-1.2).

[0018] Through extensive experimentation, the inventors discovered that the epoxy resin matrix using a blend of bisphenol A and bisphenol F epoxy resins in this application not only reduces the system viscosity to improve filler dispersion and workability but also increases the crosslinking density to compensate for the potential decrease in heat resistance caused by the introduction of flexible cashew phenol segments, thus ensuring the adhesive maintains sufficient modulus at high temperatures. Bisphenol A epoxy resin has good toughness but high viscosity, while bisphenol F epoxy resin has high crosslinking density and low viscosity. When blended in the aforementioned ratio, the low-viscosity bisphenol F resin effectively dilutes the high-viscosity bisphenol A resin, reducing the overall application viscosity of component A and facilitating filler wetting and uniform dispersion of POSS nanoparticles. Simultaneously, the high crosslinking density provided by bisphenol F resin compensates for the crosslinking point dilution effect caused by the introduction of long alkyl side chains of cashew phenol, maintaining the thermomechanical strength of the network. Furthermore, the similarity in molecular structure between the two resins allows them to form a uniform co-crosslinked network during curing, avoiding phase separation and achieving synergistic optimization of process performance and overall mechanical properties after curing.

[0019] When the proportion of bisphenol A type epoxy resin is too high, the system viscosity is too high, filler dispersion is difficult, POSS nanoparticles are prone to agglomeration, and the workability deteriorates. At the same time, insufficient crosslinking density makes it difficult to compensate for the decrease in heat resistance caused by the introduction of cashew phenol flexible segments. After curing, the modulus of the adhesive layer decreases significantly at high temperatures, and its ability to withstand high-temperature conditions such as reflow soldering is weakened. In addition, air bubbles in the high-viscosity system are not easy to remove, and residual pores may remain inside the adhesive layer after curing, affecting mechanical properties and bonding reliability. When the proportion of bisphenol A type epoxy resin is too high, its own crystallization tendency will also appear during low-temperature storage or transportation, which may lead to resin precipitation and delamination, affecting product stability.

[0020] When the proportion of bisphenol F epoxy resin is too high, the crosslinking density of the system is too large, and the cured network is too rigid. Although the heat resistance is improved, the toughness is reduced. The toughening effect of the flexible segments of cashew phenol is suppressed by the overly rigid network, and the elongation at break and impact resistance are reduced, making it difficult to achieve a balance between rigidity and toughness. At the same time, an excessively high proportion of bisphenol F will increase the brittleness of the system, making it prone to brittle fracture when subjected to impact or thermal cycling stress. Furthermore, an excessively high crosslinking density may lead to increased curing shrinkage stress, making it easy for peeling or cracking to occur at the interface.

[0021] Therefore, controlling the mass ratio of the two within the range of 1:(0.8-1.2) is one of the important conditions for achieving the rigid-tough balance characteristics of this application.

[0022] In one specific implementation, the silane coupling agent is KH-560.

[0023] By adopting the above technical solution, the epoxy groups in KH-560 molecules can participate in the curing reaction of components A and B, and together with the epoxy groups of POSS-modified epoxy resin, they are cross-linked by the amine groups of cashew phenol-modified polyamide resin through ring-opening, thereby anchoring the silane coupling agent in the cross-linked network in the form of covalent bonds. Simultaneously, the silanol groups generated after hydrolysis of KH-560 can undergo condensation reactions with the hydroxyl groups on the surfaces of inorganic fillers such as calcium carbonate and fumed silica, forming a strong organic-inorganic interface bond. They can also chemically bond with the hydroxyl groups or oxides on the surfaces of substrates such as metals and ceramics, significantly improving the adhesion between the adhesive and the substrate. Through the bridging effect of KH-560, the interfacial compatibility between the organic and inorganic phases, and between the adhesive layer and the substrate, is optimized, effectively reducing interfacial defects and improving the overall mechanical reliability and environmental aging resistance of the adhesive.

[0024] In one specific implementation scheme, the reactive toughening diluent is cashew phenol glycidyl ether, which is prepared by reacting cashew phenol with epichlorohydrin and has an epoxy value of 0.30-0.45 mol / 100g.

[0025] The inventors discovered that by using cashew phenol glycidyl ether as a reactive toughening diluent, the long alkyl side chain of cashew phenol in its molecular structure is homologous to the cashew phenol side chain of the cashew phenol-modified polyamide resin in component B. The two have excellent thermodynamic compatibility before curing and can spontaneously entangle with each other to avoid phase separation. During the curing process, the epoxy groups of cashew phenol glycidyl ether participate in the epoxy-amine crosslinking reaction, and permanently introduce the flexible side chain into the network through covalent bonds. This not only reduces the viscosity of the system and improves the dispersion uniformity of the filler and POSS nanoparticles, but also provides additional flexible suspension segments for the crosslinking network, forming a gradient toughening structure with "soft and hard combination" with the rigid POSS skeleton. Compared to ordinary inert diluents (such as butyl glycidyl ether), cashew phenol glycidyl ether does not migrate or degrade strength, and its epoxy value is controlled within the range of 0.30-0.45 mol / 100g, which can ensure that an appropriate amount of active groups participate in the reaction. This avoids excessive reaction leading to an excessively short pot life, while ensuring sufficient crosslinking degree, thereby synergistically improving the elongation at break and impact resistance of the adhesive, without sacrificing the high temperature modulus.

[0026] Secondly, this application provides a method for preparing a two-component epoxy adhesive, employing the following technical solution: A method for preparing a two-component epoxy adhesive includes the following steps: S1-2. Mix bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified epoxy resin, calcium carbonate, silane coupling agent, fumed silica, and reactive toughening diluent evenly, and degas under vacuum to obtain component A. S2-2. Mix the modified polyamide resin, polyetheramine curing agent, calcium carbonate, and fumed silica evenly, and degas under vacuum to obtain component B. S3-2. Mix component A and component B to obtain the two-component epoxy adhesive.

[0027] The two-component epoxy adhesive prepared by mixing using the above steps has the characteristics of uniform dispersion of each component and good storage stability. It can be quickly cured by mixing in proportion when used, and the operation is simple. After curing, the POSS rigid skeleton and cashew phenol flexible side chain in the adhesive layer form an interpenetrating network, which has both high shear strength and high elongation at break, and maintains stable bonding performance in a wide temperature range alternating environment.

[0028] In one specific implementation scheme, in step S3-2, the mass ratio of component A to component B is 1:(0.8-1.2).

[0029] By adopting the above technical solution, the mass ratio of component A to component B is controlled within the range of 1:(0.8-1.2), which can make the stoichiometric ratio of epoxy groups to amine groups close to the theoretical value, ensuring complete curing reaction and dense cross-linking network, thereby obtaining the best comprehensive mechanical properties and heat resistance. If the ratio deviates from this range, it may lead to incomplete curing or too low cross-linking density, decrease in high temperature modulus, or too fast reaction, resulting in too short pot life and difficult operation.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. This application uses a modified epoxy resin containing a cage-like polysilsesquioxane structure and a cashew phenol modified polyamide resin containing terminal amine groups to form an interpenetrating network of "rigid nanoframework and flexible long-chain side chains" through an epoxy-amine curing reaction. This allows the adhesive to maintain high shear strength while significantly improving elongation at break, achieving a balance between rigidity and toughness that is difficult to achieve in traditional epoxy systems.

[0031] 2. This application effectively reduces the viscosity of the system and improves the dispersibility of fillers and POSS nanoparticles by compounding bisphenol A and bisphenol F epoxy resins in a specific ratio and introducing cashew phenol glycidyl ether as a reactive toughening diluent. At the same time, the interfacial adhesion and impact toughness of the adhesive layer are further enhanced by the mutual entanglement and covalent anchoring of homologous long chains. Detailed Implementation

[0032] The present application will be further described in detail below with reference to embodiments and comparative examples: Some of the raw materials used in the examples and comparative examples: Dimer acid (CAS: 61788-89-4), diethylenetriamine (CAS: 111-40-0), KH-560 (full name: γ-(2,3-epoxypropoxy)propyltrimethoxysilane (CAS: 2530-83-8), and butyl glycidyl ether (CAS: 2426-08-6) are all from Shanghai Maclean. Bisphenol A type epoxy resin, model YD-128, and bisphenol F type epoxy resin, model YDF-170, are both produced by Dongguan Baineng New Materials Co., Ltd. Calcium carbonate, model number ML-1003, is from Xintu Chemical. Cashew phenol (purity: 94.3%, grade: 1007C, from Changshu Naisu Biomaterials Technology Co., Ltd.); Fumed silica (model: R202, purchased from Evonik Degussa AG); Polyetheramine curing agent (model: D230, purchased from Shandong Yousuo Chemical Technology Co., Ltd.); Polyamide resin (alcohol-soluble resin, grade: 650, purchased from Jinan Jingyu Chemical Co., Ltd.)

[0033] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products.

[0034] Preparation Example 1 The preparation steps of modified epoxy resin are as follows: S1-1. Dissolve 100g KH-560 in 0.4L ethanol, add 30mL water, and adjust the pH to 3 with acetic acid. Stir and hydrolyze at 50℃ for 3 hours to obtain a hydrolysate containing silanol groups. S2-1. Heat the above hydrolysate to 70°C, add 5g of 25wt% tetramethylammonium hydroxide aqueous solution and continue the reaction for 9 hours to form a cage-type polysilsesquioxane prepolymer containing epoxy groups. S3-1. The cage-like polysilsesquioxane prepolymer was mixed with 500g of bisphenol A type epoxy resin, and the solvent and water were removed by vacuum distillation at 90℃ to obtain an epoxy resin containing a cage-like polysilsesquioxane structure. (Testing showed that the epoxy resin containing the cage-like polysilsesquioxane structure, as a modified epoxy resin, has an epoxy value of 0.47 mol / 100g.) Preparation Example 2 The preparation steps of the modified polyamide resin are as follows: 100g of dimer acid, 36g of diethylenetriamine, and 26g of cashew nut phenol were mixed and reacted at 155°C for 3 hours under nitrogen protection, followed by a further increase in temperature to 220°C for another 3 hours. After the reaction, the mixture was vacuum dehydrated at 220°C for 1 hour, then cooled to below 100°C and discharged to obtain modified polyamide resin. The amine value of the prepared modified polyamide resin was measured to be 200 mg KOH / g.

[0035] Preparation Example 3 The preparation of cashew phenol glycidyl ether is as follows: 100g of cashew nut shell powder, 225g of epichlorohydrin, and 2g of benzyltriethylammonium chloride were mixed and heated to 80℃ with stirring for 4 hours. After the reaction was completed, the temperature was lowered to 60℃, and 50g of 32% NaOH aqueous solution was added dropwise over 2 hours. After the addition was completed, the reaction was continued at 6℃ for 3 hours. After the reaction was completed, the reaction solution was filtered to remove impurities, allowed to stand and separate into layers, and the organic phase was washed with deionized water until neutral. The solution was then distilled under reduced pressure at 90℃ to obtain cashew nut shell powder glycidyl ether. The epoxy value of the prepared cashew nut shell powder glycidyl ether was determined to be 0.37 mol / 100g. Example Example 1

[0036] The preparation method of the two-component epoxy adhesive is as follows: S1-2. Mix 30 parts by weight of bisphenol A type epoxy resin, 30 parts by weight of bisphenol F type epoxy resin, 50 parts by weight of the modified epoxy resin prepared in Preparation Example 1, 20 parts by weight of calcium carbonate, 3.5 parts by weight of KH-560, 7.5 parts by weight of fumed silica, and 12.5 parts by weight of cashew phenol glycidyl ether prepared in Preparation Example 3 evenly, and degas under vacuum to obtain component A. S2-2. Mix 45 parts by weight of the modified polyamide resin prepared in Preparation Example 2, 20 parts by weight of polyetheramine curing agent, 20 parts by weight of calcium carbonate, and 7.5 parts by weight of fumed silica evenly, and degas under vacuum to obtain component B. S3-2. Mix component A and component B at a mass ratio of 1:1 to obtain a two-component epoxy adhesive. Example 2

[0037] The only difference between Example 2 and Example 1 is that in step S1-2 of Example 2, 30 parts by weight of bisphenol A epoxy resin and 30 parts by weight of bisphenol F epoxy resin are replaced with 40 parts by weight of bisphenol A epoxy resin and 20 parts by weight of bisphenol F epoxy resin. Example 3

[0038] The only difference between Example 3 and Example 1 is that in step S1-2 of Example 3, 30 parts by weight of bisphenol A type epoxy resin and 30 parts by weight of bisphenol F type epoxy resin are replaced with 20 parts by weight of bisphenol A type epoxy resin and 40 parts by weight of bisphenol F type epoxy resin. Example 4

[0039] The only difference between Example 4 and Example 1 is that in step S1-2 of Example 4, 30 parts by weight of bisphenol A type epoxy resin and 30 parts by weight of bisphenol F type epoxy resin are replaced with 60 parts by weight of bisphenol A type epoxy resin. Example 5

[0040] The only difference between Example 5 and Example 1 is that in step S1-2 of Example 5, 30 parts by weight of bisphenol A epoxy resin and 30 parts by weight of bisphenol F epoxy resin are replaced with 60 parts by weight of bisphenol F epoxy resin. Example 6

[0041] The only difference between Example 6 and Example 1 is that in step S1-2 of Example 6, 12.5 parts by weight of the cashew phenol glycidyl ether prepared in Example 3 is replaced with 12.5 parts by weight of butyl glycidyl ether.

[0042] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that in steps S1-2 of Comparative Example 1, 50 parts by weight of the modified epoxy resin prepared in Example 1 are replaced with 50 parts by weight of type A epoxy resin, which, combined with the original 30 parts by weight of bisphenol A epoxy resin, makes a total of 80 parts by weight of bisphenol A epoxy resin.

[0043] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that in step S2-2 of Comparative Example 2, 45 parts by weight of the modified polyamide resin prepared in Example 2 are replaced with 45 parts by weight of polyamide resin.

[0044] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that in step S1-2 of Comparative Example 3, 50 parts by weight of the modified epoxy resin prepared in Example 1 are replaced with 50 parts by weight of type A epoxy resin, which, combined with the original 30 parts by weight of bisphenol A epoxy resin, makes a total of 80 parts by weight of bisphenol A epoxy resin; at the same time, in step S2-2, 45 parts by weight of the modified polyamide resin prepared in Example 2 are replaced with 45 parts by weight of polyamide resin.

[0045] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that in step S1-2 of Comparative Example 4, 50 parts by weight of the modified epoxy resin prepared in Example 1 are replaced with 50 parts by weight of type A epoxy resin, which, combined with the original 30 parts by weight of bisphenol A epoxy resin, makes a total of 80 parts by weight of bisphenol A epoxy resin; at the same time, 12.5 parts by weight of the cashew phenol glycidyl ether prepared in Example 3 in step S1-2 are replaced with 12.5 parts by weight of butyl glycidyl ether.

[0046] The two-component epoxy adhesives prepared in each embodiment and comparative example were used as samples for performance testing according to the following standards: 1. Shear strength test Referring to GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)", two standard metal steel specimens were used to form a specimen by overlapping and bonding the specimens. The specimens were then assembled on a tensile testing machine, and the specimen failure time was controlled between 45s and 85s. The maximum failure load was recorded, and the shear strength of each specimen was calculated. 2. Elongation at break test Each sample was cast into a standard dumbbell shape. Referring to GB / T 2567-2021 "Test Method for Performance of Resin Castings", after conditioning for 24 hours at (23±2)℃ and (50±5)% relative humidity, it was continuously loaded at a tensile speed of 2mm / min until the sample broke. The elongation at break (unit: %) was recorded. Each group of tests had no less than 5 valid samples, and the arithmetic mean was taken. 3. Temperature resistance test The prepared shear specimens and dumbbell-shaped specimens were placed in a high-low temperature alternating test chamber and subjected to a temperature cycle of -40℃ (holding for 30 minutes) → 260℃ (holding for 30 minutes), for a total of 1000 cycles. After the cycle, the shear strength and elongation at break of the specimens were tested according to GB / T7124-2008 and GB / T 2567-2021, respectively, and the retention rate was calculated by comparing them with the room temperature specimens that had not undergone temperature cycling, using the following formula: Retention rate (%) = (test value of sample after cycling / test value of sample at room temperature without cycling) × 100%.

[0047] Table 1. Two-component epoxy adhesives prepared in each example and comparative example.

[0048] Based on Examples 1-6 and Table 1, it can be seen that the mixing ratio of bisphenol A type epoxy resin to bisphenol F type epoxy resin has a significant impact on the overall performance of the adhesive. When the mass ratio of the two is 1:1, the room temperature shear strength, elongation at break, and temperature change resistance are all optimal. An excessively high proportion of bisphenol A leads to excessively high system viscosity, insufficient crosslinking density, and a decrease in high-temperature resistance; an excessively high proportion of bisphenol F results in an overly rigid network, reducing elongation at break and temperature change resistance. Therefore, controlling the mass ratio of bisphenol A type epoxy resin to bisphenol F type epoxy resin within the range of 1:(0.8-1.2) is an important condition for achieving a balance between rigidity and toughness, as well as resistance to high and low temperatures. Compared to ordinary butyl glycidyl ether, cashew phenol glycidyl ether is used as a reactive toughening diluent. Because the long alkyl side chain of cashew phenol is homologous and compatible with the cashew phenol-modified polyamide of component B, it can form an intertwined flexible network during the curing process, which synergistically toughens with the rigid skeleton of POSS, thus significantly improving room temperature strength, high temperature retention rate and thermal cycling retention rate.

[0049] Combined with Examples 1 and Comparative Examples 1-4, and with Table 1, it can be seen that this application achieves a balance between rigidity and toughness that is difficult to achieve in traditional epoxy systems by synergistically compounding the cage-type polysilsesquioxane-modified epoxy resin in component A with the cashew phenol-modified polyamide resin in component B. The two form an interpenetrating network of "rigid nanoframework-flexible long-chain side chains" through epoxy-amine curing reaction, which enables the adhesive to significantly improve the elongation at break while maintaining high shear strength. Although Comparative Example 1 added cashew phenol glycidyl ether and component B was cashew phenol-modified polyamide, the lack of a POSS rigid-toughened framework resulted in high shear strength but elongation at break not reaching the optimal value. Comparative Example 2, although component A was POSS-modified epoxy and cashew phenol glycidyl ether was added, lacked the flexible energy storage and interfacial buffering effect of the long alkyl side chains of cashew phenol due to the use of ordinary polyamide resin in component B. Comparative Example 3 used neither, resulting in the lowest performance across all categories. Comparative Example 4, although component B was cashew phenol-modified polyamide, lacked both a POSS rigid framework and a cashew phenol homologous diluent. This fully demonstrates that only by organically combining the POSS rigid framework and the flexible segments of cashew phenol through an epoxy-amine curing reaction with covalent bonds, supplemented by cashew phenol glycidyl ether as a homologous toughening bridge, can a microphase topology of alternating "rigid nodes-flexible side chains" be formed in the crosslinked network. POSS rigid nodes bear loads and resist high-temperature creep; cashew phenol flexible side chains absorb impact and buffer thermal stress; cashew phenol glycidyl ether not only reduces system viscosity and improves filler dispersion, but also achieves synergistic effect by intertwining with component B with its homologous long chain.

[0050] This application utilizes a POSS-modified epoxy resin to construct a rigid-tough balance, cashew phenol-modified polyamide resin to introduce flexible side chains, and cashew phenol glycidyl ether to achieve homologous toughening. It also incorporates bisphenol A / F epoxy resin to balance processability and crosslinking density. These three components form an alternating microphase topology of "rigid nodes and flexible side chains" through an epoxy-amine curing reaction: POSS nanocages maintain modulus at high temperatures, cashew phenol long chains dissipate energy under impact and maintain flexibility at low temperatures, and the homologous long chains of cashew phenol glycidyl ether prevent phase separation. At the interface, POSS silanol hydroxyl groups anchor the substrate at multiple points, while the hydrophobic enrichment of cashew phenol long chains forms a flexible buffer layer. It is this "rigid-flexible" design that enables this application to achieve high strength, high toughness, and resistance to alternating high and low temperatures—qualities unattainable by traditional systems—across a wide temperature range.

[0051] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A two-component epoxy adhesive, characterized in that, The product comprises component A and component B. Component A includes the following components in parts by weight: 40-80 parts epoxy resin matrix, 30-70 parts modified epoxy resin, 10-30 parts calcium carbonate, 2-5 parts silane coupling agent, 5-10 parts fumed silica, and 5-20 parts reactive toughening diluent. Component B includes the following components in parts by weight: 30-60 parts modified polyamide resin, 10-30 parts polyetheramine curing agent, 10-30 parts calcium carbonate, and 5-10 parts fumed silica. The modified epoxy resin is an epoxy resin containing a cage-like polysilsesquioxane structure, and the modified polyamide resin is a cashew nut phenol-modified polyamide resin containing terminal amine groups.

2. The two-component epoxy adhesive according to claim 1, characterized in that, The modification and preparation steps of the modified epoxy resin are as follows: S1-1. Dissolve KH-560 in an organic solvent, add water and an acidic catalyst, adjust the pH to 3-4, and carry out a hydrolysis reaction to obtain a hydrolysate containing silanol groups. S2-1. The hydrolysate containing silanol groups obtained in step S1-1 is heated to 60-80°C and polycondensation reaction is continued to form a cage-type polysilsesquioxane prepolymer containing epoxy groups. S3-1. The cage-type polysilsesquioxane prepolymer containing epoxy groups obtained in step S2-1 is mixed with epoxy resin, and then post-treated to obtain the modified epoxy resin.

3. The two-component epoxy adhesive according to claim 1, characterized in that, The modification and preparation steps of the modified polyamide resin are as follows: The modified polyamide resin is obtained by melt polycondensation reaction of dimer acid, diethylenetriamine, and cashew phenol, followed by post-treatment.

4. The two-component epoxy adhesive according to claim 1, characterized in that, In the modification step of the modified polyamide resin, the mass ratio of dimer acid, diethylenetriamine, and cashew phenol is 100:(27-45):(10-42).

5. The two-component epoxy adhesive according to claim 1, characterized in that, The epoxy resin matrix includes bisphenol A type epoxy resin and bisphenol F type epoxy resin.

6. The two-component epoxy adhesive according to claim 5, characterized in that, The mass ratio of the bisphenol A type epoxy resin to the bisphenol F type epoxy resin is 1:(0.8-1.2).

7. The two-component epoxy adhesive according to claim 1, characterized in that, The silane coupling agent is KH-560.

8. The two-component epoxy adhesive according to claim 1, characterized in that, The reactive toughening diluent is cashew phenol glycidyl ether, which is prepared by reacting cashew phenol with epichlorohydrin and has an epoxy value of 0.30-0.45 mol / 100g.

9. A method for preparing a two-component epoxy adhesive according to any one of claims 1-8, characterized in that, Includes the following steps: S1-2. Mix bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified epoxy resin, calcium carbonate, silane coupling agent, fumed silica, and reactive toughening diluent evenly, and degas under vacuum to obtain component A. S2-2. Mix the modified polyamide resin, polyetheramine curing agent, calcium carbonate, and fumed silica evenly, and degas under vacuum to obtain component B. S3-2. Mix component A and component B to obtain the two-component epoxy adhesive.

10. The method for preparing the two-component epoxy adhesive according to claim 1, characterized in that, In step S3-2, the mass ratio of component A to component B is 1:(0.8-1.2).

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