A single-component epoxy adhesive with high bonding strength and low coefficient of thermal expansion and a preparation method thereof

Abstract

The application belongs to the field of adhesives, and particularly relates to a single-component epoxy adhesive with high adhesion and low thermal expansion coefficient and a preparation method thereof. The single-component epoxy adhesive with high adhesion and low thermal expansion coefficient comprises the following raw material components: epoxy resin, hyperbranched modified toughening agent, filler, silane coupling agent, curing agent and curing accelerator. The filler comprises amino-silica, carboxylated cellulose nanofiber and spherical alumina. In order to improve the poor adhesion of the existing epoxy adhesive to the electronic module, the epoxy adhesive has high adhesion and low thermal expansion coefficient, the adhesive is toughened, the cold and hot impact resistance effect is good, the phenomenon of debonding and cracking under cold and hot cycles is avoided, and the stability and reliability of adhesion are improved.

Description

Technical Field

[0001] This application belongs to the field of adhesives, specifically relating to a single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion and its preparation method. Background Technology

[0002] Liquid crystal polymer (LCP) materials, with their high temperature resistance, low water absorption, low coefficient of thermal expansion, and excellent mechanical and dielectric properties, have become key materials in high-end electronics, aerospace, and other fields. In microelectronics and semiconductor packaging, components such as chip packaging substrates, connectors, and 5G base station RF devices need to withstand the high temperatures of reflow soldering and have extremely high dimensional accuracy requirements. In automotive electronics and new energy, sensor housings and high-frequency connectors for charging piles need to withstand a wide range of temperature fluctuations. In optics and consumer electronics, mobile phone camera modules have stringent requirements for dimensional stability and must possess a low coefficient of thermal expansion to prevent optical shifts. These applications place even stricter demands on the performance of adhesives.

[0003] When existing epoxy adhesives are applied to LCP substrates, the low surface energy of LCP results in poor wetting properties, leading to insufficient interfacial adhesion and low shear strength, which cannot meet the requirements of some applications with high adhesion strength. Furthermore, the coefficient of thermal expansion (CTE) of ordinary epoxy differs significantly from that of LCP; ordinary epoxy has a CTE of 50-80 ppm / ℃, while LCP is only 3-10 ppm / ℃. Under thermal cycling, the interface may debond and crack, severely affecting product reliability and service life. Simultaneously, the high crosslinking brittleness of epoxy combined with the rigidity of LCP causes stress concentration, leading to adhesive layer brittleness. While traditional toughening methods can improve the toughness of cured epoxy resins, they lower the glass transition temperature (GTE), affecting heat resistance and limiting their use in high-temperature environments. Core-shell rubber toughening agents, although having good heat resistance, have high viscosity; if added in large quantities, it is difficult to add sufficient fillers to reduce the system's CTE, making it difficult to simultaneously achieve high adhesion and a low CTE. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion, and a method for preparing the same.

[0005] In a first aspect, this application provides a one-component epoxy adhesive with high adhesion and low coefficient of thermal expansion, employing the following technical solution: A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive, comprising the following raw material components in parts by weight: 20-60 parts epoxy resin, 40-60 parts hyperbranched modified toughening agent, 50-100 parts filler, 5-10 parts silane coupling agent, 30-60 parts curing agent, and 10-30 parts curing accelerator; the filler includes aminated wollastonite, carboxylated cellulose nanofibers, and spherical alumina.

[0006] In this application, the hyperbranched toughening agent in the single-component epoxy adhesive can reduce the viscosity of the system to improve wettability and promote adhesion, and can also cooperate with the filler components to help disperse stress. Aminated wollastonite, carboxylated cellulose nanofibers and spherical alumina work together to form a rigid skeleton, reducing the coefficient of thermal expansion, so that the adhesive can have both high adhesion and low coefficient of thermal expansion, making it suitable for a variety of fields with high requirements for dimensional stability and bond strength.

[0007] The needle-like morphology of wollastonite can interlock to form a rigid framework within the composite material. During curing, the amino groups of aminated wollastonite and the carboxyl groups of carboxylated cellulose nanofibers undergo an amidation reaction to form a continuous rigid framework, reducing the coefficient of thermal expansion. Spherical alumina can effectively fill the gaps in this rigid framework, increasing the tortuosity of the thermal movement path of resin segments not completely bound by chemical bonds, thus improving temperature resistance. Through modification, the overall filler is anchored in the cross-linked network, inhibiting the overall expansion of the resin. This gives the entire filler network binding ability on the adhesive matrix, improving the filling and dispersibility of the filler in the epoxy system, avoiding local thermal expansion differences, inhibiting the thermal movement of chain segments, and significantly reducing the overall coefficient of thermal expansion. Silane coupling agents can improve the adhesion between the adhesive and the substrate, while curing agents and curing accelerators help the adhesive cure, increase temperature resistance, and lower the curing temperature.

[0008] Preferably, the preparation method of the hyperbranched modified toughening agent includes the following steps: adding terminal hydroxyl hyperbranched polyester and polyetheramine to toluene, and reacting at 130-140℃ for 4-6 hours under nitrogen protection, cooling to 60-80℃, adding 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate and triphenylphosphine dropwise, and reacting at 100-110℃ for 3-4 hours to obtain the hyperbranched modified toughening agent.

[0009] More preferably, the mass ratio of the hydroxyl-terminated hyperbranched polyester to 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate is (0.5-0.6):1.

[0010] The hyperbranched toughening agent is mainly composed of hydroxyl-terminated hyperbranched polyester, grafted with polyetheramine segments and end-capped with epoxy, forming a three-dimensional structure with numerous branching points. Adding the hyperbranched toughening agent to the matrix reduces the system viscosity, allowing the adhesive to fully wet the low surface energy liquid crystal polymer substrate. The terminal alicyclic epoxy groups can interact with the liquid crystal polymer surface, forming multi-point chemical anchoring between the adhesive layer and the substrate, improving interfacial bonding strength. The polyetheramine segments have a low glass transition temperature, maintaining flexibility even at low temperatures, forming dispersed flexible regions in the cured crosslinked network. When external forces are applied, these flexible regions are flexibly released through the segments. Motion absorbs energy, preventing crack initiation caused by stress concentration, and greatly enhances the shear force of the epoxy adhesive system, achieving a balance between rigidity and toughness. This improves the adhesive's toughness, strength, and resistance to thermal shock. Simultaneously, the alicyclic epoxy groups at the ends of the hyperbranched toughening agent can react with the amino groups on the surface of the aminated wollastonite, anchoring it to the filler surface and forming a rigid skeleton to flexible segments and then to the resin network structure. This allows the expansion-inhibiting effect of the rigid skeleton to be transferred to the entire resin network through the flexible segments, buffering thermal stress. Together with the filler, it reduces the adhesive's coefficient of thermal expansion, improving overall performance. When temperature changes, the rigid skeleton resists expansion, the flexible segments buffer stress, and the hyperbranched toughening agent and filler work together to inhibit thermal expansion and resist damage, thus preventing the adhesive layer from cracking due to thermal stress concentration. This allows the adhesive to achieve both high adhesion and a low coefficient of thermal expansion on liquid crystal polymer substrates. Therefore, if the content of hydroxyl-terminated hyperbranched polyester is too high, it will increase the rigidity of the hyperbranched modified toughening agent, make it unable to effectively disperse stress, and easily cause cracks, affecting the adhesive performance and service life of the adhesive. If the content of hydroxyl-terminated hyperbranched polyester is too low, it will result in insufficient rigid skeleton and reaction sites in the toughening agent, leading to poor toughening effect of the adhesive. This will cause the adhesive to be prone to debonding and cracking under thermal cycling, reducing its dimensional stability and reliability.

[0011] Preferably, the preparation method of aminated wollastonite includes: dispersing wollastonite in N,N-dimethylformamide, then adding it to an N,N-dimethylformamide solution containing p-aminobenzoic acid, and reacting at 100-120℃ for 6-10 hours under nitrogen protection to obtain aminated wollastonite.

[0012] Preferably, the preparation method of carboxylated cellulose nanofibers includes: dispersing cellulose nanofibers in N,N-dimethylformamide, then adding epichlorohydrin and tetrabutylammonium bromide, adjusting the pH to 10-11 under nitrogen protection, reacting at 60-80℃ for 3-6 hours, then redispersing the product in N,N-dimethylformamide, adding p-aminobenzoic acid, and reacting at 60-80℃ for 8-10 hours to obtain carboxylated cellulose nanofibers.

[0013] Preferably, the mass ratio of aminated wollastonite, carboxylated cellulose nanofibers, and spherical alumina is (5-7):(4-6):(1-2).

[0014] The adhesive utilizes a combination of three fillers: aminated wollastonite, carboxylated cellulose nanofibers, and spherical alumina. Aminated wollastonite and carboxylated cellulose nanofibers are linked by amide bonds to form a continuous rigid framework, while spherical alumina fills the gaps in the framework, increasing the tortuosity of the thermal motion path, reducing the thermal expansion coefficient of the adhesive, and creating a denser, more bound network. Furthermore, during curing, it can react with the hydroxyl groups in the epoxy resin matrix or the hydroxyl groups of the hyperbranched toughening agent, anchoring the filler within the resin network, binding the resin chain movement, and transferring the low thermal expansion characteristics to the entire system. Therefore, if the content of carboxylated cellulose nanofibers is too low, the number of amide bonds decreases, the continuity of the rigid framework is insufficient, stress cannot be effectively transferred through the continuous framework, leading to localized stress concentration, easier crack propagation, decreased shear strength, and easy brittle fracture of the adhesive layer. Conversely, excessive spherical alumina content increases the hardness of the adhesive layer, decreases its flexibility, increases its brittleness, and raises the overall thermal expansion coefficient. This reduces the ability to absorb thermal stress through deformation under thermal shock, making it prone to interfacial debonding or brittle cracking.

[0015] Preferably, the epoxy resin includes bisphenol A type epoxy resin and bisphenol F type epoxy resin in a mass ratio of 1:(0.8-1.2).

[0016] It can enable adhesives to have the strength properties of epoxy adhesives and help other raw materials to play a better role in the system. Together with hyperbranched modifiers, toughening agents, fillers and other raw materials, it can achieve the effect of high adhesion and low coefficient of thermal expansion of adhesives.

[0017] Preferably, the curing agent is 4,4'-diaminodiphenyl sulfone and the curing accelerator is 2-methylimidazole.

[0018] Secondly, this application provides a method for preparing a one-component epoxy adhesive with high adhesion and low coefficient of thermal expansion, using the following technical solution: A method for preparing a one-component epoxy adhesive with high adhesion and low coefficient of thermal expansion includes the following steps: taking epoxy resin, hyperbranched modifier and toughening agent, filler, silane coupling agent, curing agent and curing accelerator in proportion, mixing each component, stirring evenly, grinding, vacuum degassing and then heating to cure, thus obtaining a one-component epoxy adhesive with high adhesion and low coefficient of thermal expansion.

[0019] Preferably, the heat curing process involves heating at 140-150℃ for 2-4 hours, followed by heating at 180-200℃ for 1-2 hours.

[0020] In summary, this application has the following beneficial effects: 1. The hyperbranched toughening agent of this application reduces the viscosity of the system to improve wettability and promote adhesion, and can be combined with filler components to help disperse stress; amino-modified wollastonite, carboxylated cellulose nanofibers and spherical alumina work together to form a rigid skeleton, reducing the coefficient of thermal expansion, so that the adhesive can have both high adhesion and low coefficient of thermal expansion, making it suitable for a variety of fields with high requirements for dimensional stability and bond strength.

[0021] 2. The three fillers, aminated wollastonite, carboxylated cellulose nanofibers and spherical alumina, work synergistically. Aminated wollastonite and carboxylated cellulose nanofibers are connected by amide bonds to form a continuous rigid framework, while spherical alumina fills the gaps in the framework, increasing the tortuosity of the thermal motion path, reducing the thermal expansion coefficient of the adhesive, and forming a denser binding network. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the embodiments.

[0023] raw material Some of the raw materials used in the preparation examples and embodiments: The hydroxyl-terminated hyperbranched polyester HBP-OH was purchased from Xi'an Ruixi Biotechnology Co., Ltd.; the bisphenol A epoxy resin grade EP-4901E was from Adico, Japan; the bisphenol F epoxy resin grade YL983U was from Mitsubishi Chemical, Japan; the silane coupling agent was KH-560; the nanocellulose grade D4234 was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the wollastonite (1250 mesh) was purchased from Dalian Huanqiu Minerals Co., Ltd.; the spherical alumina grade LF-Al2O3-N20 was purchased from Ningbo Luofei Nanotechnology Co., Ltd.; the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate grade ERL-4221; unless otherwise specified, all raw materials used in the examples and comparative examples were conventional products that could be purchased commercially.

[0024] Preparation Example 1 Preparation of hyperbranched modified toughening agent: 25 parts of hydroxyl-terminated hyperbranched polyester and 16 parts of polyetheramine were added to 100 parts of toluene. The mixture was heated to 135℃ and stirred for 6 hours under nitrogen protection. After vacuum distillation, the mixture was cooled to 80℃. Under nitrogen protection, 50 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate and 0.5 parts of triphenylphosphine were added dropwise. The mixture was heated to 110℃ and reacted for 3 hours. After vacuum distillation at 50℃, the mixture was dried under vacuum at 60℃ for 12 hours to obtain the hyperbranched modified toughening agent.

[0025] Preparation Example 2 Preparation of hyperbranched modified toughening agent: 20 parts of hydroxyl-terminated hyperbranched polyester and 16 parts of polyetheramine were added to 100 parts of toluene. The mixture was heated to 135℃ and stirred for 6 hours under nitrogen protection. After vacuum distillation, the mixture was cooled to 80℃. Under nitrogen protection, 55 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate and 0.5 parts of triphenylphosphine were added dropwise. The mixture was heated to 110℃ and reacted for 3 hours. After vacuum distillation at 50℃, the mixture was dried under vacuum at 60℃ for 12 hours to obtain the hyperbranched modified toughening agent.

[0026] Preparation Example 3 Preparation of hyperbranched modified toughening agent: 35 parts of hydroxyl-terminated hyperbranched polyester and 16 parts of polyetheramine were added to 100 parts of toluene. The mixture was heated to 135℃ and stirred for 6 hours under nitrogen protection. After vacuum distillation, the mixture was cooled to 80℃. Under nitrogen protection, 40 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate and 0.5 parts of triphenylphosphine were added dropwise. The mixture was heated to 110℃ and reacted for 3 hours. After vacuum distillation at 50℃, the mixture was dried under vacuum at 60℃ for 12 hours to obtain the hyperbranched modified toughening agent.

[0027] Preparation Example 4 Preparation of aminated wollastonite: 10 parts of wollastonite were added to 100 parts of N,N-dimethylformamide and ultrasonically dispersed for 30 min. Then, 15 parts of N,N-dimethylformamide solution containing 2 parts of p-aminobenzoic acid were added. The mixture was heated to 120℃ under nitrogen protection and reacted for 8 h. The mixture was then filtered, washed with anhydrous ethanol, and vacuum dried at 60℃ for 12 h to obtain aminated wollastonite.

[0028] Preparation Example 5 Preparation of aminated wollastonite: 10 parts of wollastonite were added to 100 parts of toluene and ultrasonically dispersed for 30 min. 60 parts of ethanol containing 2 parts of γ-aminopropyltrimethoxysilane were added to adjust the pH to 5 with glacial acetic acid and stirred for 30 min. The mixture was heated to 80℃ and stirred for 6 h under nitrogen protection. After washing with ethanol, the mixture was vacuum dried at 60℃ for 12 h to obtain aminated wollastonite.

[0029] Preparation Example 6 Preparation of carboxylated cellulose nanofibers: 20 parts of cellulose nanofibers were added to 150 parts of N,N-dimethylformamide and ultrasonically dispersed for 1 h. Then, 30 parts of epichlorohydrin and 0.5 parts of tetrabutylammonium bromide were added. Under nitrogen protection, 10% sodium hydroxide solution was slowly added dropwise to adjust the pH to 10. The reaction was carried out at 60℃ for 6 h. After filtration and washing with water, the product was redispersed in 150 parts of N,N-dimethylformamide. 20 parts of p-aminobenzoic acid were added and the reaction was carried out at 80℃ for 8 h. The product was washed with N,N-dimethylformamide and ethanol, and then vacuum dried at 50℃ for 8 h to obtain carboxylated cellulose nanofibers. Example 1

[0030] A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 4, a carboxylated cellulose nanofiber prepared in Preparation Example 6, and spherical alumina in a mass ratio of 5:4:2. Example 2

[0031] A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 4, a carboxylated cellulose nanofiber prepared in Preparation Example 6, and spherical alumina in a mass ratio of 7:2:2. Example 3

[0032] A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 4, a carboxylated cellulose nanofiber prepared in Preparation Example 6, and spherical alumina in a mass ratio of 3:4:4. Example 4

[0033] A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 2, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 4, a carboxylated cellulose nanofiber prepared in Preparation Example 6, and spherical alumina in a mass ratio of 5:4:2. Example 5

[0034] A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 3, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 4, a carboxylated cellulose nanofiber prepared in Preparation Example 6, and spherical alumina in a mass ratio of 5:4:2. Example 6

[0035] A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 5, a carboxylated cellulose nanofiber prepared in Preparation Example 6, and spherical alumina in a mass ratio of 5:4:2.

[0036] Comparative Example 1 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is wollastonite in a mass ratio of 5:4:2, carboxylated cellulose nanofibers prepared in Preparation Example 6, and spherical alumina.

[0037] Comparative Example 2 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite, cellulose nanofibers, and spherical alumina prepared in Preparation Example 4 in a mass ratio of 5:4:2.

[0038] Comparative Example 3 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is an aminated wollastonite prepared in Preparation Example 4 and a carboxylated cellulose nanofiber prepared in Preparation Example 6 in a mass ratio of 7:4.

[0039] Comparative Example 4 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a mass ratio of 1:1; the filler is aminated wollastonite and spherical alumina prepared in Preparation Example 4 in a mass ratio of 9:2.

[0040] Comparative Example 5 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a 1:1 mass ratio of bisphenol A type epoxy resin and bisphenol F type epoxy resin; the filler is a 9:2 mass ratio of carboxylated cellulose nanofibers and spherical alumina prepared in Preparation Example 6.

[0041] Comparative Example 6 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin in a 1:1 mass ratio; the filler is aminated wollastonite prepared in Preparation Example 4.

[0042] Comparative Example 7 A high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive comprises the following steps: taking 40 parts epoxy resin, 50 parts hyperbranched modified toughening agent prepared in Preparation Example 1, 75 parts filler, 8 parts silane coupling agent, 45 parts curing agent, and 20 parts curing accelerator, mixing the components, maintaining a vacuum of 0.01 MPa, stirring at 600 r / min for 3 h, maintaining a vacuum of -0.095 MPa, stirring at 300 r / min for 1 h, and removing air bubbles, thus obtaining the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive. The epoxy resin is a 1:1 mass ratio of bisphenol A type epoxy resin and bisphenol F type epoxy resin; the filler is carboxylated cellulose nanofibers prepared in Preparation Example 6.

[0043] The performance of the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesives prepared in Examples 1-6 and Comparative Examples 1-7 was tested using the following methods: a. Shear strength: In accordance with GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)", the single-component epoxy adhesive product of the above example was prepared, heated and cured at 150°C for 2 hours, and then heated to 180°C for 1 hour; the shear strength against LCP was tested. b. In accordance with the national standard GB / T 36800.2-2018 "Plastics Thermomechanical Analysis (TMA) Part 2: Determination of Linear Thermal Expansion Coefficient and Glass Transition Temperature", the single-component epoxy adhesives of the examples and comparative examples were heated to 150℃ for 2 hours and then heated to 180℃ for 1 hour to fully cure. The coefficient of thermal expansion was tested using a thermomechanical analyzer (TMA). c. Thermal shock test: LCP lap shear specimens were prepared and cured at 150℃ for 2 hours, then heated to 180℃ and cured for another hour. The test conditions were -40℃ / 80℃, 1 cycle / h, 240 cycles. After the cycle, the specimens were removed and allowed to return to room temperature. The shear strength retention rate was then tested. Shear strength retention rate = shear strength after high-temperature cycling / initial shear strength × 100%. Performance is shown in Table 1. Table 1 Performance Test Results

[0044] As shown in Table 1, the epoxy adhesives prepared in the examples exhibit high adhesion and a low coefficient of thermal expansion. The adhesives are toughened and exhibit excellent resistance to thermal shock, preventing delamination and cracking under thermal cycling. This improves the dimensional stability and reliability of LCP substrates. Comparing Examples 1-3 and Comparative Examples 1-7, it is believed that the amino-modified wollastonite and carboxylated cellulose nanofibers are linked by amide bonds to form a continuous rigid framework. Spherical alumina fills the gaps in the framework, increasing the tortuosity of the thermal motion path, reducing the coefficient of thermal expansion of the adhesive, and forming a denser, more bound network. Furthermore, the modified filler components can react with the hydroxyl groups in the epoxy resin matrix and the hyperbranched toughening agent during curing, anchoring the filler in the resin network, binding the resin chain movement, and transferring the low thermal expansion characteristics to the entire system. Comparing Examples 1 and 6, it can be seen that the primary amino groups on the surface of aminated wollastonite can undergo amidation reactions with the carboxyl groups on the surface of carboxylated cellulose nanofibers to construct a continuous rigid framework and reduce the coefficient of thermal expansion. The propyl chain in Example 6 is a flexible segment, and these soft spots may deform when the temperature changes, weakening the framework's efficiency in inhibiting thermal expansion. Para-aminobenzoic acid contains a rigid benzene ring structure, and the rigid connecting arms make the stress transfer between wollastonite and amide bonds more direct, resulting in a higher efficiency of the framework in inhibiting thermal expansion.

[0045] Comparing Examples 1 and 4-5, the addition of hyperbranched modified toughening agent to the matrix can reduce the viscosity of the system, allowing the adhesive to fully wet the low surface energy liquid crystal polymer substrate. The alicyclic epoxy groups at the ends can interact with the surface of the liquid crystal polymer, forming multi-point chemical anchoring between the adhesive layer and the substrate, improving the interfacial bonding strength. When the temperature changes, the rigid skeleton resists expansion, and the flexible chain segments buffer stress. The hyperbranched modified toughening agent and the filler work together to suppress thermal expansion and resist damage, thereby preventing the adhesive layer from cracking due to thermal stress concentration.

[0046] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A one-component epoxy adhesive with high adhesion and low coefficient of thermal expansion, characterized in that: The high-adhesion, low-thermal-expansion coefficient single-component epoxy adhesive comprises the following raw material components in parts by weight: 20-60 parts epoxy resin, 40-60 parts hyperbranched modified toughening agent, 50-100 parts filler, 5-10 parts silane coupling agent, 30-60 parts curing agent, and 10-30 parts curing accelerator; the filler includes aminated wollastonite, carboxylated cellulose nanofibers, and spherical alumina.

2. The single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion according to claim 1, characterized in that: The preparation method of the hyperbranched modified toughening agent includes the following steps: adding terminal hydroxyl hyperbranched polyester and polyetheramine to toluene, and reacting at 130-140℃ for 4-6 hours under nitrogen protection, cooling to 60-80℃, adding 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate and triphenylphosphine, and reacting at 100-110℃ for 3-4 hours to obtain the hyperbranched modified toughening agent.

3. The single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion according to claim 2, characterized in that: The mass ratio of the hydroxyl-terminated hyperbranched polyester to 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate is (0.5-0.6):

1.

4. The single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion according to claim 1, characterized in that: The mass ratio of the aminated wollastonite, carboxylated cellulose nanofibers, and spherical alumina is (5-7):(4-6):(1-2).

5. The single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion according to claim 1, characterized in that: The epoxy resin includes bisphenol A type epoxy resin and bisphenol F type epoxy resin in a mass ratio of 1:(0.8-1.2).

6. The single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion according to claim 1, characterized in that: The curing agent is 4,4'-diaminodiphenyl sulfone, and the curing accelerator is 2-methylimidazole.

7. A method for preparing the high-adhesion, low-thermal-expansion coefficient single-component epoxy adhesive according to any one of claims 1-6, characterized in that, Includes the following steps: Take epoxy resin, hyperbranched modifier and toughening agent, filler, silane coupling agent, curing agent and curing accelerator in proportion, mix the components, stir evenly, grind, degas under vacuum, and heat to cure, which is a single-component epoxy adhesive with high adhesion and low coefficient of thermal expansion.

8. The method for preparing the high-adhesion, low-thermal-expansion-coefficient one-component epoxy adhesive according to claim 7, characterized in that: The heating and curing process involves heating at 140-150℃ for 2-4 hours, followed by heating at 180-200℃ for 1-2 hours.

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