High-temperature-resistant and high-toughness epoxy adhesive film and preparation method thereof

Abstract

The present application relates to a kind of high-temperature-resistant high-toughness epoxy film and its preparation method, belong to epoxy film technical field.The mixture of magnesium phosphate and glucose and montmorillonite is calcined at high temperature, the high-temperature-resistant performance and mechanical strength of filler are significantly improved, the carbon film formed by carbonization of glucose reduces the agglomeration of filler, improves dispersibility and compatibility;Carbon fiber is pretreated by nitric acid, the interface bonding force of resin matrix and calcined montmorillonite is enhanced, the overall toughness of composite filler is improved;Composite filler forms skeleton structure in resin matrix, effectively improves the toughness and high-temperature resistance of epoxy film.In addition, by adding polyamide acid in epoxy resin, using the characteristics that polyamide acid molecular chain segment can keep good mechanical properties at high temperature, by forming semi-interpenetrating network structure or chemical bond effect, the high-temperature resistance and toughness of epoxy resin are further improved;The prepared epoxy film is suitable for various high-temperature, high-toughness application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of epoxy film technology, and relates to a high-temperature resistant and high-toughness epoxy film and its preparation method. Background Technology

[0002] Epoxy films, as a single-component epoxy adhesive containing a latent curing agent, achieve bonding and curing through a cross-linking polymerization reaction initiated by heating. Due to their high bonding rigidity and wide applicability, they occupy an important position in aerospace, high-speed rail interior decoration, and cruise ship manufacturing. Traditional liquid epoxy adhesives, due to uneven application and cumbersome operation by hand, have gradually been optimized into dry-process single-component epoxy films, aiming to improve ease of operation and uniformity. However, current epoxy film products on the market face many technical challenges. For example, traditional epoxy films are prone to embrittlement, deformation, and even failure at high temperatures, failing to meet the requirements of some high-temperature environments. Simultaneously, their toughness is relatively poor, making them unable to withstand significant external impacts or vibrations, thus limiting their application in complex stress environments. Summary of the Invention

[0003] The purpose of this invention is to provide a high-temperature resistant and high-toughness epoxy film and its preparation method, which has the characteristics of high toughness, high temperature resistance, and simple and environmentally friendly manufacturing process.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A high-temperature resistant and high-toughness epoxy film, wherein the epoxy film is formulated as follows (by weight): 55-65 parts modified liquid epoxy resin, 20-30 parts solid epoxy resin, 5-10 parts composite filler, 3-5 parts compatibilizer, 2-3 parts curing agent, and 0.5-1 part accelerator.

[0006] The preparation method of the composite filler is as follows:

[0007] S1-1: Place 10-15 parts by weight of montmorillonite in 85-90 parts by weight of deionized water, sonicate for 30 min, then add 1-3 parts by weight of magnesium phosphate pentahydrate and 0.5-1 parts by weight of glucose, sonicate at 90℃ for 1.5 h, let stand at room temperature for 1 h, wash with deionized water and dry in a vacuum drying oven at 60℃, then calcine in a muffle furnace, and then ball mill for 1-2 h at a ball milling speed of 400-500 r / min to obtain powder A;

[0008] S1-2: Add 3-5 parts by weight of carbon fiber to 20-30 parts by weight of nitric acid solution, sonicate for 30 min, wash with deionized water until the pH of the eluent is 7, and dry in a vacuum drying oven at 60°C for 6 h to obtain the pretreated carbon fiber.

[0009] S1-3: Mix powder A and pretreated carbon fiber, place in a ball mill and ball mill for 1.5 hours at a speed of 500-600 r / min, and pass through a 200-mesh sieve to obtain the composite filler.

[0010] Furthermore, the calcination temperature in the muffle furnace in S1-1 is 400-500℃, and the calcination time is 30 minutes.

[0011] Furthermore, the concentration of the nitric acid solution in S1-2 is 2M.

[0012] Furthermore, in S1-3, powder A and pretreated carbon fiber are mixed at a mass ratio of 2:1.

[0013] Furthermore, the preparation method of the modified liquid epoxy resin is as follows:

[0014] The temperature was raised to 70°C and 10-15 parts by weight of polyamic acid were added to 50-60 parts by weight of liquid bisphenol A epoxy resin under stirring conditions of 800-1000 r / min. 0.5-1 parts by weight of 1M acetic acid solution was added dropwise and stirring was maintained for 1.5-2 h to obtain the modified liquid epoxy resin.

[0015] Furthermore, the solid epoxy resin is one or more of solid bisphenol A epoxy resin, solid bisphenol F epoxy resin, and solid bisphenol S epoxy resin.

[0016] Furthermore, the compatibilizer is one of the silane coupling agents KH550, KH560, and KH570.

[0017] Furthermore, the curing agent is ultrafine dicyandiamide.

[0018] Furthermore, the accelerator is an imidazole curing accelerator.

[0019] A method for preparing a high-temperature resistant and high-toughness epoxy film includes the following steps:

[0020] S10-1: Mix the modified liquid epoxy resin, solid epoxy resin, composite filler and coupling agent according to the formula ratio, heat to 70℃ and stir at 750~850r / min for 30min, then add curing agent and accelerator, maintain at 70℃ and stir at 850~950r / min for 1h to obtain the adhesive.

[0021] S10-2: Apply the adhesive to the polytetrafluoroethylene film and allow it to air dry naturally to obtain the high-temperature resistant and high-toughness epoxy film.

[0022] In the preparation of the composite filler, magnesium phosphate and glucose are first mixed with montmorillonite and calcined in a high-temperature environment. Under high temperature, magnesium phosphate decomposes to produce magnesium oxide and water. Magnesium oxide is a high-melting-point compound that significantly improves the high-temperature resistance of the filler. Simultaneously, because the radius of magnesium ions is similar to that of the original cations in the montmorillonite interlayer, some magnesium ions can displace the original cations and enter the montmorillonite interlayer to form magnesium silicates. This process not only changes the interlayer structure of montmorillonite but also enhances the mechanical strength of the filler through the chemical bonds formed between magnesium ions and silicates. Furthermore, glucose undergoes a carbonization reaction at high temperature, forming a carbonaceous film that coats the surface of the filler particles. This carbonaceous film not only reduces the agglomeration of filler particles and improves their dispersibility in the resin matrix but also enhances the compatibility between the filler and the resin matrix. Carbon fiber, as another reinforcing material, needs to be pretreated with nitric acid before being added. Nitric acid removes impurities from the carbon fiber surface and increases its surface area and roughness through etching, thereby improving the interfacial bonding between the carbon fiber and the resin matrix, as well as between the calcined montmorillonite and the carbon fiber itself. This strong interfacial bonding helps carbon fibers effectively transfer and disperse stress when subjected to external forces, thereby improving the overall toughness of the composite filler. The composite filler forms a skeletal structure within the resin matrix, which can significantly improve the toughness and high-temperature resistance of the epoxy film.

[0023] When polyamic acid and epoxy resin are mixed, their molecular chains interact through both physical entanglement and chemical bonding. Physical entanglement refers to the interweaving and winding of polyamic acid and epoxy resin molecular chains in space, forming a semi-interpenetrating network structure. Chemical bonding occurs between the carboxyl groups of polyamic acid and the epoxy groups of epoxy resin. With the interaction between the polyamic acid and epoxy resin molecular chains, the crosslinking density of the system gradually increases, resulting in more crosslinking points in the epoxy resin system and a tighter connection between molecular chains, thereby improving the overall performance of the material. Furthermore, the amide groups in the polyamic acid molecular chains possess high thermal stability, maintaining good mechanical properties at high temperatures. When polyamic acid and epoxy resin form a semi-interpenetrating network structure, this thermal stability is transferred throughout the entire system. Simultaneously, due to the increased crosslinking density, the movement of molecular chains is restricted, reducing the possibility of slippage and breakage at high temperatures, significantly improving the high-temperature resistance of the epoxy resin. The addition of polyamic acid salts can also improve the microstructure of epoxy resins. By optimizing the mixing process and reaction conditions, the molecular segments of polyamic acid and epoxy resin are more uniformly and densely distributed at the microscale, thereby helping to improve the overall performance and stability of the material. When subjected to external impact, the polyamic acid molecular segments can absorb and disperse energy through deformation and slippage, thus playing a toughening role. This allows the epoxy resin to maintain high strength and hardness while also possessing strong flexibility and impact resistance. Furthermore, the reaction between polyamic acid and epoxy resin can generate groups that promote the curing of epoxy resin, lowering the curing temperature of the system.

[0024] The beneficial effects of this invention are:

[0025] (1) High-melting-point magnesium oxide is generated by calcining magnesium phosphate with glucose and montmorillonite at high temperature, and magnesium silicate is formed by replacing the interlayer cations of montmorillonite. This significantly improves the high temperature resistance and mechanical properties of the filler. At the same time, the carbon film formed by the carbonization of glucose reduces the agglomeration of the filler and improves its dispersibility and compatibility. After the carbon fiber is pretreated with nitric acid, the interfacial bonding force with the resin matrix and the calcined montmorillonite is enhanced, which further improves the overall toughness of the composite filler. The skeleton structure formed by the composite filler in the resin matrix effectively improves the toughness and high temperature resistance of the epoxy film.

[0026] (2) The addition of polyamic acid can improve the high temperature resistance and toughness of epoxy resin. Through the formation of a semi-interpenetrating network structure or chemical bonding, the polyamic acid molecular chain segments can maintain good mechanical properties at high temperature and absorb and disperse external impacts. Detailed Implementation

[0027] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0028] In the following examples and comparative examples:

[0029] Solid bisphenol A epoxy resin, solid bisphenol F epoxy resin, solid bisphenol S epoxy resin, and liquid bisphenol A epoxy resin: purchased from Jiaxing Oriental Resin Factory;

[0030] Silane coupling agents KH550, KH560, and KH570 were purchased from Hebei Yanxi Chemical Co., Ltd.

[0031] Ajinomoto Latent Curing Agent MY-25: Purchased from Benlong Trading (Tianjin) International Trade Co., Ltd.;

[0032] Polytetrafluoroethylene membrane: purchased from Forsmann Scientific (Beijing) Co., Ltd.;

[0033] Ultrafine dicyandiamide: purchased from Wuhan Xinyang Ruihe Chemical Technology Co., Ltd.;

[0034] Polyamic acid: purchased from Merck Group in Darmstadt, Germany;

[0035] Acetic acid: purchased from Merck Group in Darmstadt, Germany;

[0036] Carbon fiber: purchased from Beijing Mairuida Technology Co., Ltd.

[0037] Montmorillonite: purchased from Jiangsu Sinopharm Pharmaceutical Co., Ltd.;

[0038] Magnesium phosphate pentahydrate: purchased from Shanghai Haohong Biomedical Technology Co., Ltd.;

[0039] Glucose: Purchased from CSPC Shengxue Glucose Co., Ltd.

[0040] Example 1

[0041] A high-temperature resistant and high-toughness epoxy film, wherein the epoxy film formulation 1 is as follows (by weight): 60 parts modified liquid epoxy resin, 25 parts solid bisphenol A epoxy resin, 7 parts composite filler, 4 parts silane coupling agent KH550, 2.5 parts ultrafine dicyandiamide, and 0.7 parts Ajinomoto latent curing agent MY-250.

[0042] The preparation method of the composite filler is as follows:

[0043] S1-1: Place 12 parts by weight of montmorillonite in 87 parts by weight of deionized water, sonicate for 30 min, then add 2 parts by weight of magnesium phosphate pentahydrate and 0.7 parts by weight of glucose, sonicate at 90℃ for 1.5 h, let stand at room temperature for 1 h, wash with deionized water and dry in a vacuum drying oven at 60℃, then calcine in a muffle furnace at 450℃ for 30 min, and then ball mill in a ball mill for 1.5 h at a speed of 450 r / min to obtain powder A;

[0044] S1-2: Add 4 parts by weight of carbon fiber to 25 parts by weight of 2M nitric acid solution, sonicate for 30 min, wash with deionized water until the pH of the eluent is 7, and dry in a vacuum drying oven at 60°C for 6 h to obtain the pretreated carbon fiber.

[0045] S1-3: Mix powder A and pretreated carbon fiber at a mass ratio of 2:1, place them in a ball mill and ball mill for 1.5 hours at a speed of 550 r / min, and pass them through a 200-mesh sieve to obtain the composite filler.

[0046] The modified liquid epoxy resin is prepared as follows.

[0047] The temperature was raised to 70°C and 12 parts by weight of polyamic acid were added to 55 parts by weight of liquid bisphenol A epoxy resin under stirring at 900 r / min. 0.7 parts by weight of 1M acetic acid solution was added dropwise and stirring was maintained for 1.7 h to obtain the modified liquid epoxy resin.

[0048] A method for preparing a high-temperature resistant and high-toughness epoxy film includes the following steps:

[0049] S10-1: Mix modified liquid epoxy resin, solid bisphenol A epoxy resin, composite filler, and silane coupling agent KH550 according to formula 1, heat to 70℃ and stir at 800r / min for 30min, then add ultrafine dicyandiamide and Ajinomoto latent curing agent MY-25, maintain at 70℃ and stir at 900r / min for 1h to obtain the adhesive.

[0050] S10-2: Apply the adhesive to the polytetrafluoroethylene film and allow it to air dry naturally to obtain the high-temperature resistant and high-toughness epoxy film.

[0051] Example 2

[0052] A high-temperature resistant and high-toughness epoxy film, wherein the epoxy film formulation 2 is as follows (by weight): 55 parts modified liquid epoxy resin, 20 parts solid bisphenol F epoxy resin, 5 parts composite filler, 3 parts silane coupling agent KH560, 2 parts ultrafine dicyandiamide, and 0.5 parts Ajinomoto latent curing agent MY-250.

[0053] The preparation method of the composite filler is as follows:

[0054] S1-1: Place 10 parts by weight of montmorillonite in 85 parts by weight of deionized water, sonicate for 30 min, then add 1 part by weight of magnesium phosphate pentahydrate and 0.5 parts by weight of glucose, sonicate at 90℃ for 1.5 h, let stand at room temperature for 1 h, wash with deionized water and dry in a vacuum drying oven at 60℃, then calcine in a muffle furnace at 400℃ for 30 min, then ball mill in a ball mill for 1 h at a speed of 400 r / min to obtain powder A;

[0055] S1-2: Add 3 parts by weight of carbon fiber to 20 parts by weight of 2M nitric acid solution, sonicate for 30 min, wash with deionized water until the pH of the eluent is 7, and dry in a vacuum drying oven at 60°C for 6 h to obtain the pretreated carbon fiber.

[0056] S1-3: Mix powder A and pretreated carbon fiber at a mass ratio of 2:1, place in a ball mill and ball mill for 1.5 hours at a speed of 500 r / min, and pass through a 200-mesh sieve to obtain the composite filler.

[0057] The modified liquid epoxy resin is prepared as follows.

[0058] The temperature was raised to 70°C and 10 parts by weight of polyamic acid were added to 50 parts by weight of liquid bisphenol A epoxy resin under stirring at 800 r / min. 0.5 parts by weight of 1M acetic acid solution was added dropwise and stirring was maintained for 1.5 h to obtain the modified liquid epoxy resin.

[0059] A method for preparing a high-temperature resistant and high-toughness epoxy film includes the following steps:

[0060] S10-1: Mix modified liquid epoxy resin, solid bisphenol F epoxy resin, composite filler, and silane coupling agent KH560 according to formula 2, heat to 70℃ and stir at 750 r / min for 30 min, then add ultrafine dicyandiamide and Ajinomoto latent curing agent MY-25, maintain at 70℃ and stir at 850 r / min for 1 h to obtain the adhesive.

[0061] S10-2: Apply the adhesive to the polytetrafluoroethylene film and allow it to air dry naturally to obtain the high-temperature resistant and high-toughness epoxy film.

[0062] Example 3

[0063] A high-temperature resistant and high-toughness epoxy film, wherein the epoxy film formulation 3 is as follows (by weight): 65 parts modified liquid epoxy resin, 30 parts solid bisphenol S epoxy resin, 10 parts composite filler, 5 parts silane coupling agent KH570, 3 parts ultrafine dicyandiamide, and 1 part Ajinomoto latent curing agent MY-25.

[0064] The preparation method of the composite filler is as follows:

[0065] S1-1: Place 15 parts by weight of montmorillonite in 90 parts by weight of deionized water, sonicate for 30 min, then add 3 parts by weight of magnesium phosphate pentahydrate and 1 part by weight of glucose, sonicate at 90℃ for 1.5 h, let stand at room temperature for 1 h, wash with deionized water and dry in a vacuum drying oven at 60℃, then calcine in a muffle furnace at 500℃ for 30 min, then ball mill in a ball mill for 2 h at a speed of 500 r / min to obtain powder A;

[0066] S1-2: Add 5 parts by weight of carbon fiber to 30 parts by weight of 2M nitric acid solution, sonicate for 30 min, wash with deionized water until the pH of the eluent is 7, and dry in a vacuum drying oven at 60°C for 6 h to obtain the pretreated carbon fiber.

[0067] S1-3: Mix powder A and pretreated carbon fiber at a mass ratio of 2:1, place in a ball mill and ball mill for 1.5 hours at a speed of 600 r / min, and pass through a 200-mesh sieve to obtain the composite filler.

[0068] The modified liquid epoxy resin is prepared as follows.

[0069] The temperature was raised to 70°C and 15 parts by weight of polyamic acid were added to 60 parts by weight of liquid bisphenol A epoxy resin under stirring at 1000 r / min. 1 part by weight of 1M acetic acid solution was added dropwise and stirring was maintained for 2 h to obtain the modified liquid epoxy resin.

[0070] A method for preparing a high-temperature resistant and high-toughness epoxy film includes the following steps:

[0071] S10-1: Mix modified liquid epoxy resin, solid bisphenol S epoxy resin, composite filler, and silane coupling agent KH570 according to formula 3, heat to 70℃ and stir at 850 r / min for 30 min, then add ultrafine dicyandiamide and Ajinomoto latent curing agent MY-25, maintain at 70℃ and stir at 950 r / min for 1 h to obtain the adhesive.

[0072] S10-2: Apply the adhesive to the polytetrafluoroethylene film and allow it to air dry naturally to obtain the high-temperature resistant and high-toughness epoxy film.

[0073] Comparative Example 1

[0074] No modification was made to the liquid epoxy resin; the remaining steps were the same as in Example 1.

[0075] Comparative Example 2

[0076] Carbon fiber was not added in the preparation of the composite filler, and the remaining steps were the same as in Example 1.

[0077] Comparative Example 3

[0078] Magnesium phosphate pentahydrate was not added during the preparation of the composite filler, and the remaining steps were the same as in Example 1.

[0079] Comparative Example 4

[0080] Without adding composite fillers, the remaining steps are the same as in Example 1.

[0081] Performance testing

[0082] The planar tensile and shear strengths of the examples and comparative examples were determined according to GB / T 1452-2005 Test Method for Tensile Strength of Sandwich Structures and GB / T 7124-1986 Test Method for Tensile Shear Strength of Adhesives. The shear test specimen was LY12 hard aluminum material with a thickness of 2.0 mm, and the aluminum plate for the planar tensile test was pure aluminum plate with a thickness of 1 mm.

[0083]

[0084] As can be seen from the examples and comparative data, the epoxy film prepared by using polyamic acid-modified liquid epoxy resin and adding calcined montmorillonite and magnesium phosphate to form a composite filler with carbon fiber has higher toughness and high temperature resistance.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-temperature-resistant and high-toughness epoxy film adhesive, characterized in that, The formula of the epoxy adhesive film is as follows: 55-65 parts by weight of modified liquid epoxy resin, 20-30 parts by weight of solid epoxy resin, 5-10 parts by weight of composite filler, 3-5 parts by weight of compatibilizer, 2-3 parts by weight of curing agent, and 0.5-1 part by weight of accelerator, The preparation method of the composite filler is as follows: S1-1: 10-15 parts by weight of montmorillonite is placed in 85-90 parts by weight of deionized water, ultrasonic for 30 min, then 1-3 parts by weight of magnesium phosphate pentahydrate and 0.5-1 parts by weight of glucose are added, ultrasonic stirring at 90℃ for 1.5h, standing at room temperature for 1h, washing with deionized water and placing in a vacuum drying oven at 60℃ for drying, then placing in a muffle furnace for calcination, and then placing in a ball mill for ball milling at 400-500r / min for 1-2h to obtain powder A; S1-2: 3-5 parts by weight of carbon fiber is added to 20-30 parts by weight of nitric acid solution, ultrasonic for 30 min, washing with deionized water until the pH of the eluent is 7, and then placing in a vacuum drying oven at 60℃ for 6h to obtain pretreated carbon fiber; S1-3: The powder A and the pretreated carbon fiber are mixed and placed in a ball mill for ball milling at 500-600r / min for 1.5h, and then sieved through a 200 mesh screen to obtain the composite filler; The preparation method of the modified liquid epoxy resin is as follows: The temperature is increased to 70℃, 10-15 parts by weight of polyamide acid is added to 50-60 parts by weight of liquid bisphenol A epoxy resin under stirring at 800-1000r / min, 0.5-1 parts by weight of 1M acetic acid solution is added dropwise, and stirring is maintained for 1.5-2h to obtain the modified liquid epoxy resin.

2. The high-temperature-resistant and high-toughness epoxy film adhesive according to claim 1, characterized in that, The temperature for calcination in the muffle furnace in S1-1 is 400-500℃, and the calcination time is 30min.

3. The high-temperature-resistant and high-toughness epoxy adhesive film according to claim 1, characterized in that, The concentration of the nitric acid solution in S1-2 is 2M.

4. The high-temperature-resistant and high-toughness epoxy adhesive film according to claim 1, characterized in that, The powder A and the pretreated carbon fiber are mixed in a mass ratio of 2:1 in S1-3.

5. The high-temperature-resistant and high-toughness epoxy adhesive film according to claim 1, characterized in that, The solid epoxy resin is one or more of solid bisphenol A epoxy resin, solid bisphenol F epoxy resin, and solid bisphenol S epoxy resin.

6. The high-temperature-resistant and high-toughness epoxy adhesive film according to claim 1, characterized in that, The compatibilizer is one of silane coupling agents KH550, KH560, and KH570.

7. The high-temperature-resistant and high-toughness epoxy adhesive film according to claim 1, characterized in that, The curing agent is ultra-fine dicyandiamide.

8. The high-temperature-resistant and high-toughness epoxy adhesive film according to claim 1, characterized in that, The accelerator is an imidazole type curing accelerator.

9. A method for preparing the high-temperature-resistant and high-toughness epoxy film adhesive according to any one of claims 1 to 8, characterized in that, The following operation steps are included: S10-1: The modified liquid epoxy resin, the solid epoxy resin, the composite filler, and the coupling agent are mixed according to the formula proportion, heated to 70℃, and stirred at a speed of 750-850r / min for 30min, then the curing agent and the accelerator are added, and stirring is maintained at 70℃ and a speed of 850-950r / min for 1h to obtain the adhesive; S10-2: The adhesive is applied on a polytetrafluoroethylene film, and naturally air-dried to obtain the high-temperature-resistant and high-toughness epoxy adhesive film.

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