Room temperature curable epoxy structural adhesive and preparation method thereof

Abstract

This invention relates to a room-temperature curable epoxy structural adhesive and its preparation method, belonging to the technical field of material preparation in civil engineering. The epoxy structural adhesive comprises component A and component B. Component A includes epoxy resin, ultraviolet absorber, antioxidant, thixotropic agent, coupling agent, inorganic filler, and fiber; component B includes phenolic amine curing agent, polyamide curing agent, accelerator, thixotropic agent, coupling agent, inorganic filler, and fiber. This invention uses a combination of phenolic amine curing agent and polyamide curing agent to synergistically improve bonding strength and durability. Simultaneously, an accelerator is added to component B to promote catalysis. The coupling agent modifies the surface of the filler, significantly improving the interfacial bonding strength between the filler and resin. The presence of the ultraviolet absorber reduces the consumption rate of the antioxidant, while the presence of the antioxidant eliminates a small amount of free radicals that the ultraviolet absorber fails to completely block. The two work synergistically to form a "prevention-interception" closed-loop protection.

Description

Technical Field

[0001] This invention belongs to the technical field of material preparation in the field of civil engineering and construction, and more specifically, relates to an epoxy structural adhesive that can be cured at room temperature and its preparation method. Background Technology

[0002] With the rapid development of infrastructure construction in China, the demand for structural reinforcement and repair in civil engineering is increasing. Epoxy structural adhesives, as a high-performance bonding material, have been widely used in engineering fields such as bridge reinforcement, high-rise building structural connections, and subway tunnels.

[0003] The core function of epoxy structural adhesives is to achieve efficient connections between new and old concrete and steel-concrete composite structures through the synergistic effect of chemical bonding and mechanical interlocking. Its main performance is reflected in three aspects: First, high-strength adhesion, with tensile strength reaching over 30MPa and steel-to-steel shear strength ≥18MPa, meeting the requirements of GB50728 standard; second, weather resistance and durability, by adding benzotriazole UV absorbers (such as UV-326) and hindered amine light stabilizers (HALS), the material can maintain over 90% of its mechanical properties in environments ranging from -40℃ to 60℃; third, construction adaptability, the thixotropic formula ensures no dripping on facades, the working time can be controlled within 30-90 minutes, and the curing speed meets construction schedule requirements.

[0004] Currently, mainstream products generally use bisphenol A type epoxy resin as the base material, such as E-51 (epoxy value 0.48-0.54 eq / 100g), combined with modified amine curing agents to form a three-dimensional network cross-linked structure. The ether bonds and hydroxyl groups in its molecular chain give the material excellent wettability, while the benzene ring structure ensures rigidity and heat resistance.

[0005] However, existing systems have significant limitations: the bisphenol A epoxy network is prone to yellowing and chain breakage under long-term ultraviolet irradiation, resulting in insufficient weather resistance; it exhibits high low-temperature brittleness; under continuous high-temperature (>80℃) environments, the cross-linked network relaxes, leading to rapid strength decay; and the raw material cost is affected by fluctuations in the price of bisphenol A, resulting in a higher overall cost compared to ordinary cement-based materials. Furthermore, it has stringent requirements for the moisture content of the substrate (<4%), and wet surface application easily leads to interfacial bubbles; some amine curing agents also exhibit VOC release and irritating odor issues. Summary of the Invention

[0006] The purpose of this invention is to provide an epoxy structural adhesive that can be cured at room temperature and its preparation method, which has the characteristics of high strength, resistance to atmospheric aging, and fatigue resistance.

[0007] The objective of this invention can be achieved through the following technical solutions: An epoxy structural adhesive that can cure at room temperature, comprising component A and component B, wherein component A comprises the following components by weight: 100 parts epoxy resin, 0.1-0.5 parts ultraviolet absorber, 0.2-1 parts antioxidant, 1.5-3 parts thixotropic agent, 1-2.5 parts coupling agent, 100-120 parts inorganic filler and 2-4 parts fiber; Component B includes the following components: The curing agent consists of 8-12 parts phenolic amine, 32-48 parts polyamide, 1-2.5 parts accelerator, 0.5-1 part thixotropic agent, 0.5-1 part coupling agent, 50-60 parts inorganic filler, and 1-2 parts fiber.

[0008] As a preferred embodiment of the present invention, the mass ratio of component A to component B is (1.9 to 2.1):1.

[0009] As a preferred embodiment of the present invention, the mass ratio of the phenolic amine curing agent to the polyamide curing agent is 1:(3.5~4.5), more preferably 1:4.

[0010] As a preferred embodiment of the present invention, the epoxy resin is selected from at least one of E-44, E-51, and E-55.

[0011] As a preferred embodiment of the present invention, the ultraviolet absorber is selected from at least one of UV-531, UV-9, UV-24, UV-326, UV-327, and UV-1130.

[0012] As a preferred embodiment of the present invention, the antioxidant is selected from at least one of antioxidant 264, antioxidant 1010, antioxidant 1076, and antioxidant 1330.

[0013] As a preferred embodiment of the present invention, the thixotropic agent is selected from at least one of hydrophobic fumed silica, pre-dispersed organic modified bentonite, and pre-melted polyamide wax.

[0014] Furthermore, the specific surface area of ​​the hydrophobic fumed silica is 100–200 m². 2 / g. Preferably, the hydrophobic fumed silica is selected from at least one of Aerosil® R972, Aerosil® R812, CAB-O-SIL® TS-720, and HDK® H2000.

[0015] Furthermore, the organically modified bentonite is treated with 90-98% ethanol for dispersion; the polyamide wax is pre-melted by heating to 75-85℃.

[0016] As a preferred embodiment of the present invention, the coupling agent is selected from at least one of KH-550 and KH-560.

[0017] As a preferred embodiment of the present invention, the inorganic filler is selected from at least one of quartz powder, heavy calcium carbonate, silica powder, calcined kaolin, and alumina.

[0018] In this process, the surface of inorganic fillers can adsorb epoxy resin molecular chains, increasing intermolecular friction and achieving physical adsorption and mechanical interlocking, thereby improving viscosity and strength. For example, the surface of quartz powder or calcium carbonate adsorbs epoxy resin molecular chains through van der Waals forces, increasing intermolecular friction, thus increasing the viscosity of the system and accelerating early strength growth.

[0019] Furthermore, the particle size D of the inorganic filler 50 The diameter is 3–15 μm, D 90 ≤35μm, specific surface area is 0.8~8m² 2 / g.

[0020] Among them, the inorganic filler selected has a small particle size and a large specific surface area, resulting in a better thickening effect. Preferably, the particle size D of the inorganic filler is... 50 Its thickness is 5~10μm, and its specific surface area is 1.5~4.5m². 2 / g.

[0021] In addition, coupling agents such as KH-550 (γ-aminopropyltriethoxysilane) generate siloxane groups (-Si(OCH2CH3)3) through hydrolysis to form silanol groups (-Si(OH)3); the silanol groups dehydrate and condense with the hydroxyl groups on the surface of the filler (quartz powder / calcium carbonate) to form -Si-O- inorganic bonds, while the amino groups (-NH2) react with the epoxy groups to form organic bonds, which greatly improves the interfacial bonding strength between the filler and the resin.

[0022] As a preferred embodiment of the present invention, the fiber is selected from at least one of glass fiber, carbon fiber, aramid fiber, and basalt fiber.

[0023] Furthermore, the length of the fiber is 3~5mm.

[0024] Fibers have the function of bridging and crack propagation inhibition. When the material is under load, the fiber consumes energy through the pull-out effect, thereby increasing the elongation at break.

[0025] As a preferred embodiment of the present invention, the phenolic amine curing agent is at least one of T-31 phenolic amine, T-33 phenolic amine, and 593 curing agent.

[0026] Among them, curing agent 593 is an adduct of diethylenetriamine and butyl glycidyl ether, with a total amine value of 500~700mgKOH / g.

[0027] As a preferred embodiment of the present invention, the polyamide curing agent is selected from at least one of PA650 polyamide curing agent and PA651 polyamide curing agent.

[0028] As a preferred embodiment of the present invention, the accelerator is selected from at least one of triethanolamine, 2-(dimethylaminomethyl)phenol, 2,4,5-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

[0029] The preparation method of the epoxy structural adhesive that can be cured at room temperature, as described above, includes the following steps: S1. Preparation of component A: S11. Mix the epoxy resin, ultraviolet absorber, antioxidant and thixotropic agent in component A to obtain a modified epoxy resin emulsion; S12. Dilute the coupling agent in component A with 1.5 to 4 times the mass of the coupling agent in alcohol, then spray it onto the surface of the premixed filler and fiber, and then place it in an oven at 100 to 110°C for 10 to 20 minutes, and then cool it to room temperature to obtain the coupling agent modified mixture. S13. Add the coupling agent modified mixture prepared in step S12 to the epoxy resin emulsion prepared in step S1, and stir to obtain component A. S2, Preparation of component B: S21. Mix the phenolic amine curing agent, polyamide curing agent, accelerator and thixotropic agent in component B to obtain a curing agent emulsion; S22. Dilute the coupling agent in component B with 1.5 to 4 times the mass of the coupling agent in alcohol, then spray it onto the surface of the premixed filler and fiber, and then place it in an oven at 100 to 110°C for 10 to 20 minutes, and then cool it to room temperature to obtain the coupling agent modified mixture. S23. Add the coupling agent modified mixture prepared in step S22 to the curing agent emulsion prepared in step S21, and stir to obtain component B. S3. Mix component A and component B to obtain the epoxy structural adhesive that can be cured at room temperature.

[0030] Further, in steps S11 and S21, the mixing refers to stirring in a mixer with a speed of 1000-1200 r / min for 10-20 minutes; in steps S13 and S23, the stirring refers to stirring in a mixer with a speed of 350-400 r / min for 10-20 minutes.

[0031] Further, in step S3, the mass ratio of component A to component B is (1.9–2.1):1. More preferably, it is 2:1.

[0032] The above-mentioned room-temperature curable epoxy structural adhesives are used in the civil engineering field. Specifically, these epoxy structural adhesives can be used for bonding, reinforcing, splicing, and repairing structures such as cover plates, guardrails, and rebar installations in civil engineering.

[0033] The beneficial effects of this invention are: (1) This invention uses a combination of phenolic amine curing agent and polyamide curing agent to synergistically improve bonding strength and durability. The primary amine group (-NH2) in the phenolic amine molecule attacks the epoxy three-membered ring of the epoxy resin, undergoing a nucleophilic addition reaction to generate a secondary amine group (-NH-) which then opens the ring to form a hydroxyl group (-OH). The phenolic ring provides a rigid framework, forming a highly cross-linked three-dimensional network, imparting compressive strength and temperature resistance to the material. The primary amine group at the end of the polyamide molecular chain reacts with the epoxy group of the epoxy resin, and the long carbon chain of the polyamide (C17-C35) interpenetrates within the rigid network, reducing internal stress and forming a "rigid-flexible" interpenetrating network with the phenolic amine, thereby increasing the bond strength retention rate after UV aging to over 85%. Component B also includes an accelerator, which acts as a catalyst. The tertiary amine, as a Lewis base, forms a charge-transfer complex with the epoxy group, accelerating the nucleophilic attack of the amine group on the epoxy group. The tertiary amine group (-N(CH3)2) activates the epoxy group, reducing the activation energy of the reaction and shortening the curing time at room temperature.

[0034] (2) In this invention, the ultraviolet absorber selectively absorbs 290-400nm ultraviolet light and converts light energy into harmless heat energy through intramolecular proton transfer, reducing the generation of photo-induced free radicals (inhibiting the source of aging); while the antioxidant captures alkyl free radicals (-R•) and peroxy free radicals (-ROO•) generated by oxidative degradation, terminating the chain reaction (blocking the propagation of aging), achieving complementary stages. That is, the ultraviolet absorber and the antioxidant achieve synergistic effect by constructing a photo-oxygen dual protection system for polymer materials: the presence of the ultraviolet absorber reduces the consumption rate of the antioxidant, while the presence of the antioxidant eliminates the small amount of free radicals that the ultraviolet absorber fails to completely block, forming a "prevention-interception" closed-loop protection.

[0035] (3) In this invention, the coupling agent modifies the surface of the filler, significantly improving the interfacial bonding strength between the filler and the resin. Furthermore, heat treatment promotes the condensation of the coupling agent, avoiding bubble defects caused by unreacted silanol groups. The fiber forms a three-dimensional skeleton in the curing system. When the material is under load, the fiber consumes energy through the pull-out effect, increasing the elongation at break. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to specific embodiments, but the scope of protection of this invention is not limited thereto. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions or according to the manufacturer's recommendations. Unless otherwise specified, all reagents and materials used are commercially available.

[0037] Example 1 An epoxy structural adhesive that can cure at room temperature is composed of component A and component B mixed in a mass ratio of 2.1:1, wherein component A comprises the following components by weight: 100 parts epoxy resin (E-44), 0.2 parts ultraviolet absorber (UV-531), 0.4 parts antioxidant (antioxidant 1010), 2.5 parts thixotropic agent (hydrophobic fumed silica), 1.2 parts coupling agent (KH-550), 105 parts filler (quartz powder), and 4 parts fiber (glass fiber).

[0038] Component B comprises the following components by weight: 8 parts of phenolic amine curing agent (T-31 phenolic amine), 32 parts of polyamide curing agent (PA650 polyamide curing agent), 1.5 parts of accelerator (triethanolamine), 1 part of thixotropic agent (hydrophobic fumed silica), 1 part of coupling agent (KH-550), 60 parts of filler (quartz powder), and 2 parts of fiber (glass fiber).

[0039] The preparation method of the above-mentioned room-temperature curable epoxy structural adhesive is as follows: S1. Preparation of component A: S11. Mix the epoxy resin, ultraviolet absorber, antioxidant and thixotropic agent in component A, and stir in a mixer at 1100 r / min for 15 minutes to obtain modified epoxy resin emulsion. S12. Dilute the coupling agent in component A with alcohol at a mass of 3.5 times the mass of the coupling agent, then spray it onto the surface of the premixed filler and fiber, and then place it in an oven at 105℃ for 15 minutes and cool it to room temperature (23±2℃) to obtain the coupling agent modified mixture. S13. Add the coupling agent modified mixture prepared in step S12 to the epoxy resin emulsion prepared in step S1, and stir in a mixer with a speed of 380 r / min for 15 min to obtain component A. S2, Preparation of component B: S21. Mix the phenolic amine curing agent, polyamide curing agent, accelerator and thixotropic agent in component B, and stir in a mixer at 1100 r / min for 15 minutes to obtain a curing agent emulsion; S22. Dilute the coupling agent in component B with alcohol at a mass of 3.5 times the mass of the coupling agent, then spray it onto the surface of the mixed filler and fiber, and place it in an oven at 105℃ for 15 minutes. After cooling to room temperature (23±2℃), the coupling agent modified mixture is obtained. S23. Add the coupling agent modified mixture prepared in step S22 to the curing agent emulsion prepared in step S21, and stir in a mixer at a speed of 380 r / min for 15 min to obtain component B; S3. Mix component A and component B at a mass ratio of 2.1:1 to obtain the epoxy structural adhesive that can be cured at room temperature.

[0040] Example 2 An epoxy structural adhesive that can cure at room temperature is composed of component A and component B mixed in a mass ratio of 1.9:1, wherein component A comprises the following components by weight: 100 parts epoxy resin (E-44), 0.1 parts ultraviolet absorber (UV-531), 0.2 parts antioxidant (antioxidant 1010), 3 parts thixotropic agent (hydrophobic fumed silica), 1 part coupling agent (KH-550), 100 parts filler (quartz powder), and 4 parts fiber (glass fiber).

[0041] Component B comprises the following components by weight: 8 parts of phenolic amine curing agent (T-31 phenolic amine), 32 parts of polyamide curing agent (PA650 polyamide curing agent), 1 part of accelerator (triethanolamine), 1 part of thixotropic agent (hydrophobic fumed silica), 0.8 parts of coupling agent (KH-550), 60 parts of filler (quartz powder), and 2 parts of fiber (glass fiber).

[0042] The preparation method of the above-mentioned room-temperature curable epoxy structural adhesive is the same as that in Example 1.

[0043] Example 3 An epoxy structural adhesive that can cure at room temperature is composed of component A and component B mixed in a mass ratio of 1.9:1, wherein component A comprises the following components by weight: 100 parts epoxy resin (E-51), 0.2 parts ultraviolet absorber (UV-9), 0.4 parts antioxidant (antioxidant 264), 2.5 parts thixotropic agent (hydrophobic fumed silica), 1.2 parts coupling agent (KH-560), 105 parts filler (heavy calcium carbonate), and 4 parts fiber (carbon fiber).

[0044] Component B comprises the following components by weight: 8 parts of phenolic amine curing agent (T-31 phenolic amine), 32 parts of polyamide curing agent (PA650 polyamide curing agent), 1.5 parts of accelerator (triethanolamine), 1 part of thixotropic agent (hydrophobic fumed silica), 0.8 parts of coupling agent (KH-550), 60 parts of filler (quartz powder), and 2 parts of fiber (glass fiber).

[0045] The preparation method of the above-mentioned room-temperature curable epoxy structural adhesive is the same as that in Example 1.

[0046] Example 4 An epoxy structural adhesive that can cure at room temperature is composed of component A and component B mixed in a mass ratio of 2:1, wherein component A comprises the following components by weight: 100 parts epoxy resin (E-44), 0.3 parts ultraviolet absorber (UV-531), 0.6 parts antioxidant (antioxidant 1010), 2 parts thixotropic agent (hydrophobic fumed silica), 1.5 parts coupling agent (KH-550), 110 parts filler (quartz powder), and 3 parts fiber (glass fiber).

[0047] Component B comprises the following components by weight: 10 parts of phenolic amine curing agent (T-33 phenolic amine), 40 parts of polyamide curing agent (PA651 polyamide curing agent), 1.5 parts of accelerator (2-(dimethylaminomethyl)phenol), 0.8 parts of thixotropic agent (hydrophobic fumed silica), 0.6 parts of coupling agent (KH-560), 55 parts of filler (heavy calcium carbonate), and 2 parts of fiber (carbon fiber).

[0048] The preparation method of the above-mentioned room-temperature curable epoxy structural adhesive is the same as that in Example 1.

[0049] Example 5 An epoxy structural adhesive that can cure at room temperature is composed of component A and component B mixed in a mass ratio of 2:1, wherein component A comprises the following components by weight: 100 parts epoxy resin (E-44), 0.4 parts ultraviolet absorber (UV-531), 0.8 parts antioxidant (antioxidant 1010), 1.5 parts thixotropic agent (hydrophobic fumed silica), 2 parts coupling agent (KH-560), 115 parts filler (quartz powder), and 3 parts fiber (glass fiber).

[0050] Component B comprises the following components by weight: 10 parts of phenolic amine curing agent (T-31 phenolic amine), 40 parts of polyamide curing agent (PA650 polyamide curing agent), 2 parts of accelerator (triethanolamine), 0.8 parts of thixotropic agent (hydrophobic fumed silica), 0.6 parts of coupling agent (KH-550), 55 parts of filler (quartz powder), and 1 part of fiber (carbon fiber).

[0051] The preparation method of the above-mentioned room-temperature curable epoxy structural adhesive is the same as that in Example 1.

[0052] Example 6 An epoxy structural adhesive that can cure at room temperature is composed of component A and component B mixed in a mass ratio of 1.9:1, wherein component A comprises the following components by weight: 100 parts epoxy resin (E-55), 0.5 parts ultraviolet absorber (UV-326), 1 part antioxidant (antioxidant 1076), 2.5 parts thixotropic agent (hydrophobic fumed silica), 2.5 parts coupling agent (KH-550), 120 parts filler (quartz powder), and 2 parts fiber (carbon fiber).

[0053] Component B comprises the following components by weight: 12 parts of phenolic amine curing agent (T-31 phenolic amine), 48 parts of polyamide curing agent (PA650 polyamide curing agent), 2.5 parts of accelerator (triethanolamine), 0.6 parts of thixotropic agent (hydrophobic fumed silica), 0.6 parts of coupling agent (KH-550), 50 parts of filler (heavy calcium carbonate), and 1 part of fiber (carbon fiber).

[0054] The preparation method of the above-mentioned room-temperature curable epoxy structural adhesive is the same as that in Example 1.

[0055] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that the phenolic amine curing agent in component B of this comparative example is 40 parts by weight, and there is no polyamide curing agent. The other components, preparation steps and parameters are the same.

[0056] Comparative Example 2 Compared with Example 1, the difference in this comparative example is that the polyamide curing agent in component B of this comparative example is 40 parts by weight, and there is no phenolic amine curing agent. The other components, preparation steps and parameters are the same.

[0057] Comparative Example 3 Compared with Example 1, the difference of this comparative example is that there is no coupling agent in components A and B of this comparative example, and in steps S12 and S22, the same amount of alcohol as in Example 1 is directly sprayed onto the surface of the premixed filler and fiber. The other components, preparation steps and parameters are the same.

[0058] Comparative Example 4 Compared to Example 1, this comparative example differs in that the coupling agent in components A and B is replaced with an equal amount of stearic acid. All other components, preparation steps, and parameters remain the same.

[0059] Comparative Example 5 Compared to Example 1, this comparative example differs in that the accelerator in component B is replaced with an equal mass of 2-ethyl-4-methylimidazole (EMI-24). All other components, preparation steps, and parameters remain the same.

[0060] Comparative Example 6 Compared to Example 1, this comparative example differs in that component A in this comparative example does not contain an ultraviolet absorber. All other components, preparation steps, and parameters are the same.

[0061] Comparative Example 7 Compared with Example 1, the difference of this comparative example is that the preparation method of this comparative example is: without going through steps S11-S13 and S21-S23, the raw materials in component A and the raw materials in component B are directly mixed at a mass ratio of 2.1:1 and stirred in a mixer at a speed of 1100 r / min for 25 minutes to obtain epoxy structural adhesive.

[0062] Comparative Example 8 Compared with Example 1, the difference in this comparative example is that the preparation method of this comparative example is as follows: S1. Dilute the coupling agent in component A and component B with alcohol at a mass of 3.5 times the mass of the coupling agent, then spray it onto the surface of the premixed filler and fiber, and place it in an oven at 105℃ for 15 minutes. After cooling to room temperature (23±2℃), the coupling agent modified mixture is obtained. S2. Add the remaining raw materials from components A and B to the coupling agent modified mixture, and stir in a mixer at 1100 r / min for 25 minutes to obtain epoxy structural adhesive. The mass ratio of components A to components B is 2.1:1.

[0063] Performance testing methods (1) Compressive strength Prepare standard compression test specimens of 80mm×10mm×4mm according to GB / T1041. After curing at 23±2℃ for 7 days, test them on a universal testing machine at a rate of 2mm / min and take the average value of 5 parallel samples.

[0064] (2) Tensile shear strength after UV aging Aluminum-aluminum lap joint specimens were prepared according to GB / T7124 (substrate: 6061-T6 aluminum alloy, surface sandblasted + acetone cleaning; lap area 12.5mm×25mm). 20 specimens were prepared in each group: 10 for initial strength testing and 10 for post-aging testing.

[0065] Unaged samples: After curing at 23±2℃ for 7 days, the initial tensile shear strength was tested according to GB / T7124 (the average value of 10 parallel samples was taken and recorded as P0).

[0066] Aging test samples: Aging with a xenon lamp according to GB / T16422.2: Irradiance 0.5W / m 2 @340nm, blackboard temperature 63±3℃, spray cycle 18min / 102min, cumulative 500h. After aging, tensile shear strength was tested according to GB / T7124 (the average value of 10 parallel samples was taken, denoted as P1). The tensile shear strength loss after UV aging was calculated according to the formula: P0 - P1.

[0067] (3) Resistance to damp heat aging Prepare aluminum-aluminum lap joint specimens according to GB / T7124, with 20 specimens prepared in each group (10 initial specimens + 10 aged specimens).

[0068] Unaged samples: Initial tensile shear strength (P0) was tested after curing at 23℃ for 7 days.

[0069] Aging test specimens: Another 10 specimens were aged in a constant temperature and humidity chamber at 85℃ and 85%RH for 168 hours (7 days); after being removed, they were placed in an environment at 23℃ and 50%RH for 24 hours, and the tensile shear strength (P1) was tested. The percentage reduction in shear strength was calculated according to the formula = [1] [(P1 / P0)]×100%.

[0070] (4) Long-term stress resistance (creep deformation value) Dumbbell-shaped tensile specimens (Type IV, gauge length L0 = 25 ± 0.5 mm) were prepared according to GB / T1040.2. Tensile creep tests were performed according to GB / T32918: continuous loading at 23 ± 1℃ and 0.5 MPa constant tensile stress for 1000 h, with real-time monitoring of gauge length deformation using a contact extensometer, and creep deformation values ​​(mm) recorded at 1000 h. Three specimens were used in each group, and the average value was taken.

[0071] (5) Curing performance test at room temperature Test conditions: ambient temperature 23±2℃, relative humidity 50±5%, 5 parallel samples per group.

[0072] According to GB / T7123.1, after mixing component A and component B in proportion, place them in an environment of 23±2℃, and use a rotational viscometer (rotor #3, 60rpm) to measure the viscosity every 5 minutes. Record the time (min) required for the viscosity to increase to twice the initial value, which is the pot life (min).

[0073] Prepare a coating according to GB / T1728 (wet film thickness 200±20μm), and determine the surface drying time (min) by touch method at 23±2℃ and 50%RH.

[0074] Aluminum-aluminum lap joint specimens were prepared according to GB / T7124, cured at 23±2℃, and the tensile shear strength (MPa) was tested after 24 hours.

[0075] The test results are shown in Table 1.

[0076] Table 1

[0077] As can be seen from the test results in Table 1, Examples 1-6 of the present invention exhibit excellent and balanced performance in key indicators such as compressive strength, strength loss after UV aging, strength loss rate after damp heat aging, and creep deformation. They also have a reasonable applicable period and rapid strength development at room temperature (23℃), and can meet the initial load-bearing requirements of engineering projects in 24 hours. They can be used for bonding, reinforcement, splicing, and repair of structures such as cover plates, guardrails, and rebar in the field of civil engineering.

[0078] In Comparative Examples 1 and 2, the use of a single curing agent led to performance imbalances. Only the phenolic amine system exhibited high brittleness (25.2% loss due to damp heat), while only the polyamide system lacked sufficient strength (compressive strength 68 MPa, creep 0.71 mm). In Comparative Examples 3 and 7, the absence of coupling agent pretreatment resulted in interfacial bonding failure, leading to a damp heat strength loss rate as high as 44.8%–47.7% and increased creep deformation to 0.95–0.99 mm. In Comparative Examples 4 and 5, the replacement of key components, and in Comparative Example 6, the absence of key components, both significantly degraded their corresponding properties. In Comparative Examples 7 and 8, due to simplified processes, insufficient interfacial optimization resulted in decreased overall performance. Furthermore, in Comparative Examples 1 and 5, the excessively short pot life and uneven strength development may cause construction difficulties. In Comparative Example 2, slow initial curing may lead to insufficient early strength.

[0079] In summary, this invention achieves a synergistic improvement in mechanical strength, environmental durability, and long-term dimensional stability of room-temperature curing epoxy structural adhesives through a combination of coupling agent grouping and pretreatment, phenolic amine / polyamide compound curing, synergistic anti-aging system, and selection of specific accelerators.

[0080] 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. An epoxy structural adhesive that can cure at room temperature, characterized in that, It includes component A and component B. By weight, component A includes the following components: 100 parts epoxy resin, 0.1-0.5 parts ultraviolet absorber, 0.2-1 parts antioxidant, 1.5-3 parts thixotropic agent, 1-2.5 parts coupling agent, 100-120 parts inorganic filler and 2-4 parts fiber; Component B includes the following components: The curing agent consists of 8-12 parts phenolic amine, 32-48 parts polyamide, 1-2.5 parts accelerator, 0.5-1 part thixotropic agent, 0.5-1 part coupling agent, 50-60 parts inorganic filler, and 1-2 parts fiber.

2. The epoxy structural adhesive that can be cured at room temperature according to claim 1, characterized in that, The mass ratio of component A to component B is (1.9–2.1):

1.

3. The epoxy structural adhesive that can be cured at room temperature according to claim 1, characterized in that, The epoxy resin is selected from at least one of E-44, E-51, and E-55; The ultraviolet absorber is selected from at least one of UV-531, UV-9, UV-24, UV-326, UV-327, and UV-1130; The antioxidant is selected from at least one of antioxidant 264, antioxidant 1010, antioxidant 1076, and antioxidant 1330; The thixotropic agent is selected from at least one of hydrophobic fumed silica, pre-dispersed organic modified bentonite, and pre-melted polyamide wax; The coupling agent is selected from at least one of KH-550 and KH-560; The inorganic filler is selected from at least one of quartz powder, heavy calcium carbonate, silica powder, calcined kaolin, and alumina; The fiber is selected from at least one of glass fiber, carbon fiber, aramid fiber, and basalt fiber; The phenolic amine curing agent is at least one of T-31 phenolic amine, T-33 phenolic amine, and 593 curing agent; The polyamide curing agent is selected from at least one of PA650 polyamide curing agent and PA651 polyamide curing agent; The accelerator is selected from at least one of triethanolamine, 2-(dimethylaminomethyl)phenol, 2,4,5-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

4. The room-temperature curable epoxy structural adhesive according to claim 1 or 3, characterized in that, The mass ratio of the phenolic amine curing agent to the polyamide curing agent is 1:(3.5~4.5).

5. The epoxy structural adhesive that can be cured at room temperature according to claim 3, characterized in that, The specific surface area of ​​the hydrophobic fumed silica is 100–200 m². 2 / g; the organic modified bentonite is treated with 90~98% ethanol for dispersion; the polyamide wax is pre-melted by heating to 75~85℃.

6. The room-temperature curable epoxy structural adhesive according to claim 1 or 3, characterized in that, The particle size D of the inorganic filler 50 The diameter is 3–15 μm, D 90 ≤35μm, specific surface area is 0.8~8m² 2 / g.

7. An epoxy structural adhesive that can be cured at room temperature according to claim 1 or 3, characterized in that, The length of the fiber is 3~5mm.

8. A method for preparing an epoxy structural adhesive that can be cured at room temperature as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: S1. Preparation of component A: S11. Mix the epoxy resin, ultraviolet absorber, antioxidant and thixotropic agent in component A to obtain a modified epoxy resin emulsion; S12. Dilute the coupling agent in component A with 1.5 to 4 times the mass of the coupling agent in alcohol, then spray it onto the surface of the premixed filler and fiber, and then place it in an oven at 100 to 110°C for 10 to 20 minutes, and then cool it to room temperature to obtain the coupling agent modified mixture. S13. Add the coupling agent modified mixture prepared in step S12 to the epoxy resin emulsion prepared in step S1, and stir to obtain component A. S2, Preparation of component B: S21. Mix the phenolic amine curing agent, polyamide curing agent, accelerator and thixotropic agent in component B to obtain a curing agent emulsion; S22. Dilute the coupling agent in component B with 1.5 to 4 times the mass of the coupling agent in alcohol, then spray it onto the surface of the premixed filler and fiber, and then place it in an oven at 100 to 110°C for 10 to 20 minutes, and then cool it to room temperature to obtain the coupling agent modified mixture. S23. Add the coupling agent modified mixture prepared in step S22 to the curing agent emulsion prepared in step S21, and stir to obtain component B. S3. Mix component A and component B to obtain the epoxy structural adhesive that can be cured at room temperature.

9. The preparation method according to claim 8, characterized in that, In steps S11 and S21, the mixing refers to stirring in a mixer with a speed of 1000-1200 r / min for 10-20 minutes; in steps S13 and S23, the stirring refers to stirring in a mixer with a speed of 350-400 r / min for 10-20 minutes. In step S3, the mass ratio of component A to component B is (1.9 to 2.1):

1.

10. The application of the room-temperature curable epoxy structural adhesive according to any one of claims 1-7 in the field of civil engineering.

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