A method for preparing long-lasting corrosion-resistant GFRP bars with organic-inorganic hybrid synergistic modification in marine environments.

Abstract

This invention belongs to the field of building materials technology, specifically relating to a long-lasting corrosion-resistant GFRP reinforcement with organic-inorganic hybrid synergistic modification in marine environments and its preparation method. In the preparation method of this invention, the modified epoxy resin is prepared by the following steps: (1) preparing modified carbon nanotubes; (2) preparing modified expanded graphite; (3) mixing hydrogen-containing silicone oil with KH560 and reacting at room temperature under alkaline catalysis to obtain organosilicon; (4) heating the epoxy resin, adding organosilicon, and stirring to obtain organosilicon epoxy resin; mixing the modified carbon nanotubes and modified expanded graphite with a curing agent to obtain a nanofiller mixture; and mixing the organosilicon epoxy resin with the nanofiller mixture. This invention, by treating GFRP reinforcement with modified epoxy resin, helps to achieve long-lasting service of highly corrosion-resistant GFRP reinforcement in harsh environments such as marine environments.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a long-lasting corrosion-resistant GFRP bar with organic-inorganic hybrid synergistic modification in marine environments and its preparation method. Background Technology

[0002] Numerous researchers have pointed out that glass fiber reinforced polymer (GFRP) bars, due to their excellent chloride salt resistance, high specific strength, and lightweight properties, have become a potential alternative to steel reinforcement in marine engineering, providing a feasible solution for improving the durability of concrete structures. However, traditional FRP bars suffer from drawbacks during long-term service in the highly alkaline environment of the pore solution within concrete, including poor resistance to damp heat and alkali, and high brittleness of the resin matrix. The outer resin matrix is ​​first eroded by water molecules and alkaline ions, triggering water absorption, swelling, plasticization, and hydrolysis reactions. This leads to a failure of the fiber and resin to work synergistically, ultimately resulting in a significant degradation of the FRP bar's performance.

[0003] Currently, some researchers have conducted research on resin matrix modification, mainly focusing on the field of anti-corrosion coatings for reinforcing bars, rather than developing methods specifically for the application of FRP bars in concrete. Furthermore, there is a lack of sufficient experimental data to guide the application of modified resin matrices in FRP-reinforced concrete systems, leading to problems such as insignificant improvements in corrosion resistance and large dispersion in modified FRP bars. In addition, most resin matrix modification schemes primarily address the brittleness and insufficient fire resistance of the resin matrix, while in-depth research on improving the alkali resistance, damp heat resistance, and synergistic effects of the resin matrix on the bond performance with fibers is lacking. Moreover, research on the durability of modified matrices applied to fiber-reinforced reinforcing bars and concrete is extremely limited. Therefore, there is an urgent need to develop a design and synthesis method for high-performance resins for FRP bar systems to effectively protect fibers from corrosive ion attack and fully realize the synergistic effect between modified FRP bars and concrete.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing long-lasting corrosion-resistant GFRP bars with organic-inorganic hybrid synergistic modification in marine environments, so as to help solve or improve the problem that GFRP bars are easily corroded and their performance deteriorates during service inside concrete.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP bars in a marine environment, comprising the following steps: I. Treating the GFRP bars with modified epoxy resin; the modified epoxy resin is prepared by a method comprising the following steps: (1) pre-dispersing carbon nanotubes in a first alkaline solution, adding poly(methylhydrosiloxane) and tetraethyl orthosilicate, and dispersing to obtain uniformly dispersed modified carbon nanotubes; (2) under vacuum environment, mixing poly(methylhydrosiloxane) and tetraethyl orthosilicate... Ethyl ester and expandable graphite are mixed, microwave-expanded, and then dispersed in a second alkaline solution to obtain modified expanded graphite; (3) Hydrogen-containing silicone oil and γ-(2,3-epoxypropoxy)propyltrimethoxysilane are mixed and reacted at room temperature under alkaline catalysis to obtain organosilicon; (4) Epoxy resin is heated, organosilicon is added, and stirred to obtain organosilicon epoxy resin; Modified carbon nanotubes and modified expanded graphite are mixed evenly with curing agent to obtain nanofiller mixture; The organosilicon epoxy resin is mixed with the nanofiller mixture to obtain the modified epoxy resin.

[0007] Beneficial effects:

[0008] The modified epoxy resin of this invention is characterized by ease of operation, resistance to damp heat, excellent salt and alkali properties, and excellent bonding performance, especially maintaining good corrosion resistance even in harsh environments. Hydrophobic modification of the nanofillers (carbon nanotubes and graphite) increases the surface roughness of the resin matrix, reduces the contact area between water droplets and the resin matrix, and improves the hydrophobicity of the resin matrix. The formation of a surface hydrophobic network reduces the interaction energy between nanofillers, improves the uniform dispersion of nanofillers in the resin matrix, and solves the agglomeration effect of traditional nanomaterials. Furthermore, the presence of nanomaterials hinders crack propagation, causing crack tips to twist and deviate, thus prolonging the erosion path of corrosive ions. The hydrophobic network can bridge the nanofiller and epoxy resin network, enhancing interfacial interaction and limiting further crack propagation. The introduction of Si-O-Si flexible segments and epoxy groups in the organosilicon can achieve both resin matrix toughness and ensure the resin's bonding performance.

[0009] This invention treats GFRP bars with modified epoxy resin, leveraging the molecular barrier and topological interlocking effect of the organic-inorganic hybrid modified polymer system (organosilicon, modified carbon nanotubes, and modified expanded graphite synergistically form a dual protection mechanism of "physical barrier + topological interlocking") to iteratively optimize the preparation process of modified GFRP bars. This significantly improves the hydrophobicity, toughness, corrosion resistance, and bonding performance of GFRP bars in alkaline environments such as seawater and sea sand concrete pore solutions, enabling high corrosion-resistant GFRP bars to serve for extended periods in harsh environments such as marine areas. Attached Figure Description

[0010] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0011] Figure 1 This is a flowchart illustrating the preparation process of a modified epoxy resin according to one embodiment of the present invention.

[0012] Figure 2 This is a flowchart illustrating the preparation process of organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP bars in a marine environment, according to one embodiment of the present invention.

[0013] Figure 3 The image shows the surface contact angle test results for the silicone / epoxy resin matrix.

[0014] Figure 4 The tensile properties of the silicone / epoxy resin matrix before and after corrosion under different corrosive environments are shown; (a) is the result of the ultimate tensile strength test, and (b) is the result of the tensile strength loss rate test.

[0015] Figure 5 Microscopic corrosion morphology of silicone / epoxy resin matrix;

[0016] Figure 6 The results of the surface contact angle test of the modified epoxy resin matrix in Comparative Examples 3-6 are shown in the figure.

[0017] Figure 7 The tensile properties of the modified epoxy resin matrix in Comparative Examples 3-6 are shown; where (a) is the result of the ultimate tensile strength test and (b) is the result of the tensile strength loss rate test.

[0018] Figure 8 The corrosion morphology of the modified epoxy resin matrix (nanomaterial content of 0.03 wt.%) in the simulated pore solution of Comparative Examples 3-6 is shown in the following figures: (a) is N (Comparative Example 1), (b) is MoS2 / PE (Comparative Example 4); (c) is CNT / PE (Comparative Example 5); (d) is EG / PE (Comparative Example 6); and (e) is SEP / PE (Comparative Example 3).

[0019] Figure 9 The images are microscopic morphology images; among them, (ad) are HRTEM and EDS images of unmodified CNTs, (eh) are HRTEM and EDS images of modified CNTs, (im) are SEM, HRTEM, EDS and SAEDP images of unmodified EG, and (nr) are SEM, HRTEM, EDS and SAEDP images of modified EG.

[0020] Figure 10The figures show the dispersibility test results of the nanofillers in the resin before and after modification; where (a) is the sample before modification and (b) is the sample after modification.

[0021] Figure 11 The figures show the surface contact angle test results of the modified epoxy resin matrix in Example 1 and Comparative Examples 7-8; where (a) is the surface contact angle and (b) is a schematic diagram of the hydrophobic mechanism.

[0022] Figure 12 The tensile properties of the modified epoxy resin matrix before and after corrosion in Examples 1 and Comparative Examples 7-8 are shown; where (a) is the tensile strength and (b) is the tensile strength retention rate.

[0023] Figure 13 The graph shows the interlaminar shear properties test results of the modified epoxy resin matrix before and after corrosion in Example 1 and Comparative Examples 7-8.

[0024] Figure 14 The fracture surface morphology of the epoxy resin matrix before and after modification is shown; among them, (a) pure epoxy resin (Comparative Example 1), (b) silicone PE / epoxy resin (Comparative Example 2-1), (c) PE-MCNT epoxy resin (Comparative Example 7), (d) PE-MEG epoxy resin (Comparative Example 8), (e) MCNTs / MEG / PE modified epoxy resin (Example 1).

[0025] Figure 15 Corrosion morphology of epoxy resin matrix before and after modification; wherein, (a) pure epoxy resin (Comparative Example 1), (b) silicone PE / epoxy resin (Comparative Example 2-1), (c) PE-MCNT epoxy resin (Comparative Example 7), (d) PE-MEG epoxy resin (Comparative Example 8), (e) MCNTs / MEG / PE modified epoxy resin (Example 1).

[0026] Figure 16 The tensile strength variation law of GFRP reinforcement in seawater sand concrete is shown; among them, (a) is the test result of ultimate tensile strength, and (b) is the test result of tensile strength retention rate.

[0027] Figure 17 The figures show the test results of the tensile failure modes of three types of reinforcement in seawater sand concrete; among them, (a) is the test result after 0 days of corrosion, (b) is the test result after 60 days of corrosion, and (c) is the test result after 120 days of corrosion.

[0028] Figure 18 The figure shows the test results of the interlaminar shear failure modes of the three types of reinforcement.

[0029] Figure 19 The cross-sectional morphology of the reinforcing steel in the concrete after 120 days of corrosion;

[0030] Figure 20 The diagram shows the variation of ultimate bond strength under corrosive conditions; (a) is the test result of ultimate bond strength, and (b) is the test result of bond strength retention rate.

[0031] Figure 21 Corrosion morphology of three types of reinforcing materials cross sections. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0033] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0034] This invention addresses the problems of easy corrosion and performance degradation of GFRP bars during their service in concrete, and provides a method for preparing long-lasting corrosion-resistant GFRP bars with organic-inorganic hybrid synergistic modification in marine environments.

[0035] The preparation method of organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention includes the following steps: I. Treating the GFRP reinforcement with modified epoxy resin; the modified epoxy resin is prepared by a method including the following steps: (1) pre-dispersing carbon nanotubes in a first alkaline solution, adding poly(methylhydrosiloxane) and tetraethyl orthosilicate, and dispersing to obtain uniformly dispersed modified carbon nanotubes; (2) mixing poly(methylhydrosiloxane) and tetraethyl orthosilicate with expandable graphite in a vacuum environment, and after microwave expansion treatment, dispersing in a first alkaline solution. In an alkaline solution, the modified expanded graphite is dispersed to obtain modified expanded graphite; (3) Hydrogen-containing silicone oil is mixed with γ-(2,3-epoxypropoxy)propyltrimethoxysilane and reacted at room temperature under alkaline catalysis to obtain organosilicon; (4) The epoxy resin is heated, organosilicon is added, and stirred to obtain organosilicon epoxy resin (after preheating the epoxy resin, organosilicon is added and stirred evenly to obtain organosilicon epoxy resin); The modified carbon nanotubes and modified expanded graphite are mixed evenly with the curing agent to obtain a nanofiller mixture; The organosilicon epoxy resin is mixed with the nanofiller mixture to obtain modified epoxy resin. In steps (1) and / or (2), an alkaline activation combined with PMHS / TEOS hydrolysis condensation is used to construct a Si-O-Si network on the surface of carbon nanotubes and expandable graphite; The grafting rate and dispersibility of the modified nanomaterials are significantly improved. In step (2), impurities on the surface of expanded graphite are removed under vacuum, and surface hydrophobic modification is carried out during microwave treatment. This helps to enhance the grafting density of hydrophobic segments between expanded graphite layers, and improve the dispersibility and hydrophobic barrier properties of modified expanded graphite in the resin matrix. In step (3), while the organosilicon toughens, epoxy groups are introduced into its modified components to ensure the interfacial bonding performance of the modified resin. The surface grafting of nanofillers enhances their surface roughness and improves the physical and chemical interlocking effect between the resin matrix surface and the fiber and concrete interface. This helps to improve the bonding strength between the organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP bar of the present invention and the concrete interface after exposure in corrosive solutions in marine environments.

[0036] In step (4), the present invention first uniformly mixes modified carbon nanotubes and modified expanded graphite with a liquid curing agent to form a pre-dispersion system, and then mixes it with epoxy resin. This helps to improve the uniformity of the dispersion of modified carbon nanotubes and modified expanded graphite in epoxy resin (if modified carbon nanotubes and modified expanded graphite are directly dispersed in epoxy resin, it will cause a clustering effect of modified carbon nanotubes and modified expanded graphite, which is not conducive to dispersion), and improves the mechanical properties of the GFRP ribs of the present invention. In addition, the present invention helps to significantly reduce viscosity and enhance fluidity by heating the epoxy resin and then mixing it with organosilicon, thereby improving the miscibility of the two. By introducing specific glycidyl ether groups (e.g., KH560) into the organosilicon, the epoxy groups introduced on the organosilicon molecular chain can participate in the ring-opening polymerization crosslinking reaction of the epoxy resin system (forming glycidyl etheroxypropyl dimethyl polyphenylsiloxane) during the blending and curing process of organosilicon and epoxy resin.

[0037] This invention treats GFRP bars with modified epoxy resin, leveraging the molecular barrier and topological interlocking effect of the organic-inorganic hybrid modified polymer system (organosilicon, modified carbon nanotubes, and modified expanded graphite synergistically form a dual protection mechanism of "physical barrier + topological interlocking") to iteratively optimize the preparation process of modified GFRP bars. This significantly improves the hydrophobicity, toughness, corrosion resistance, and bonding performance of GFRP bars in alkaline environments such as seawater and sea sand concrete pore solutions, enabling high corrosion-resistant GFRP bars to serve for extended periods in harsh environments such as marine areas.

[0038] Preferably, step (2) specifically involves: dropping PMHS and TEOS onto the surface of expanded graphite under vacuum to remove excess air between layers, allowing TEOS and PMHS to completely penetrate the layered structure through capillary action. Subsequently, expansion is performed under microwave assistance to generate expanded graphite with increased volume; finally, it is dispersed in a KOH / ethanol solution.

[0039] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, the mass of organosilicon is 5%-15% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%) of the epoxy resin; the mass of carbon nanotubes or expandable graphite is 0.01%-0.07% (e.g., 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, or 0.07%) of the epoxy resin. Preferably, the mass of organosilicon is 5% (and the mass of carbon nanotubes or expandable graphite is 0.03% of the epoxy resin).

[0040] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, in step (1), the mass ratio of poly(methylhydrosiloxane) to tetraethyl orthosilicate is 1:1-1:4 (e.g., 1:1, 1:2, 1:3 or 1:4), and the mass ratio of carbon nanotubes and / or expandable graphite to poly(methylhydrosiloxane) is 1:5-1:10 (e.g., 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10); the first alkaline solution and / or the second alkaline solution are mixed solutions of potassium hydroxide and ethanol (preferably, the first alkaline solution is a mixed solution of potassium hydroxide solution and ethanol, the concentration of potassium hydroxide solution is 0.1-0.5 mol / L, and the volume percentage of ethanol in the first alkaline solution is 70%-90%). If the proportion of tetraethyl orthosilicate (TEOS) is too high, the formed SiO2 will agglomerate, and the unreacted TEOS hydrolysis products will affect the dispersion stability; if the proportion of TEOS is too low, the crosslinking density will be insufficient, and the corrosion resistance will be affected. Both excessively high and low amounts of poly(methylhydrosiloxane) will affect the hydrolysis reaction rate and the uniformity of the hydrophobic network coating in the system.

[0041] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, in step (2), the microwave power is 600-1000W (e.g., 600W, 700W, 800W, 900W, or 1000W), and the microwave duration is 5-15s (e.g., 5s, 7s, 9s, 11s, 13s, or 15s); the second alkaline solution is a mixed solution of potassium hydroxide and ethanol. Wherein, if the microwave power is too low, the reaction may be insufficient; if the microwave power is too high, local overheating may damage the hybrid structure; if the microwave duration is too short, insufficient cross-linking of the hydrophobic network on the surface of the nanomaterial may occur; if the microwave duration is too long, it may cause oxidation of expandable graphite or degradation of PMHS.

[0042] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, in step (3), the mass ratio of hydrogen-containing silicone oil to γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) is 1:0.5-1:3 (e.g., 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3); the alkali is sodium hydroxide, and the solvent is ethanol; the reaction time at room temperature is 4-8h (e.g., 4h, 5h, 6h, 7h or 8h). If the proportion of KH560 is too high, excessive KH560 may cause the hydrolysis condensation product to self-polymerize, forming particulate precipitates, affecting the uniformity of the silicone resin; too many epoxy groups may cause uneven curing of the formed resin matrix. If the proportion of KH560 is too low, too few epoxy groups will affect the crosslinking ability and corrosion resistance of the synthesized silicone resin and epoxy resin. If the reaction time during the preparation of organosilicon is too short, the reaction between the hydrogen-containing silicone oil and KH560 will be insufficient, the hybrid network will not be fully formed, the organosilicon will have poor density, and the modification effect will be unstable. If the reaction time during the preparation of organosilicon is too long, it may lead to silane self-polymerization, reduce the utilization rate of active groups, and affect the performance of organosilicon.

[0043] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, in step (4), the mass ratio of epoxy resin to curing agent is 100:(70-90) (e.g., 100:70, 100:75, 100:80, 100:85, or 100:90); after heating to 60-80℃ (e.g., 60℃, 65℃, 70℃, 75℃, or 80℃), organosilicon is added and stirred for 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min, or 30 min). To achieve good compatibility and mixing efficiency, the mixing operation is preferably carried out under a water bath at 60℃. At this specific temperature, the viscosity of both epoxy resin and organosilicon is significantly reduced, the fluidity is enhanced, and the miscibility between them reaches its optimal state. Furthermore, by introducing specific glycidyl ether groups into the organosilicon segments, the epoxy groups introduced into the molecular chain of the modified organosilicon resin can participate in the ring-opening polymerization and cross-linking reaction of the epoxy resin system during subsequent blending and curing with epoxy resin, thereby enhancing the miscibility between organosilicon and epoxy resin.

[0044] Preferably, the epoxy resin is a bisphenol A type epoxy resin (DGEBA); the curing agent is a methyltetrahydrophthalic anhydride curing agent (MeTHPA).

[0045] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP ribs in a marine environment according to the present invention, the method further includes the following steps: II. Stirring the modified epoxy resin, transferring it to an impregnation tank, and allowing it to stand to degas; III. Arranging the glass fibers axially on a yarn feeding frame and conveying them to the impregnation tank for impregnation; IV. Adding an accelerator to the impregnation tank and mixing it evenly with the modified epoxy resin, preheating the modified epoxy resin in the impregnation tank, impregnating the glass fibers, sizing them through forming holes, and then winding them into ribs to obtain a preliminary rib material; V. Allowing the preliminary rib material to enter the curing stage for curing; VI. Cooling, pressing, and cutting the cured rib material.

[0046] Preferably, the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol accelerator (DMP-30); the mass ratio of the accelerator to the epoxy resin is (1-10):100 (e.g., 1:1, 1:3, 1:5, 1:7, 1:9 or 1:10).

[0047] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, step V includes curing, which includes preliminary curing and secondary curing. The temperature of preliminary curing is 100-140℃ (e.g., 100℃, 110℃, 120℃, 130℃, or 140℃). Secondary curing is carried out in two stages, maintaining a constant temperature of 80-120℃ (e.g., 80℃, 90℃, 100℃, 110℃, or 120℃). Matching the impregnation rate with the resin solid kinetics is a core technical challenge. The present invention divides the curing process into preliminary curing and secondary curing, with the secondary curing temperature lower than the preliminary curing temperature, forming a multi-gradient temperature curing process. The initial curing temperature ensures that the resin quickly reaches its gel point after impregnation, avoiding resin dripping or equipment adhesion during traction. The setting of the secondary curing temperature helps to suppress interfacial microcracks caused by sudden temperature changes while ensuring a degree of curing (>95%), significantly improving the mechanical properties of the reinforcement. Furthermore, the setting of curing parameters and the dynamic adaptation of the impregnation rate ensure a strict match between the viscosity window of the modified epoxy resin (η=0.5–1.5 Pa·s) and the fiber traction rate (V=0.8–1.2 m / min), eliminating pre-curing in the adhesive bath and uneven coating. This synergistic control mechanism fundamentally solves the process defects caused by the disconnect between the impregnation rate and the curing temperature, achieving continuous and stable production of high-performance reinforcing materials.

[0048] In a preferred embodiment of the method for preparing organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP reinforcement in a marine environment according to the present invention, in step III, the impregnation rate is 0.6 m / min-1.0 m / min (e.g., 0.6 m / min, 0.7 m / min, 0.8 m / min, 0.9 m / min, or 1.0 m / min); in step IV, the preheating temperature is 40-60℃ (e.g., 40℃, 45℃, 50℃, 55℃, or 60℃); in step V, curing is completed after sequentially passing through a first drying tunnel, a second drying tunnel, and a third drying tunnel. The temperature of the first drying tunnel is 100-140℃ (e.g., 100℃, 110℃, 120℃, 130℃, or 140℃), and the temperatures of the second and third drying tunnels are 80-120℃ (e.g., 80℃, 90℃, 100℃, 110℃, or 120℃), respectively; the pultrusion rate of the reinforcement during the curing process is 0.8-1.2. m / min, for example, 0.8m / min, 0.9m / min, 1m / min, 1.1m / min or 1.2m / min, and the total length of the first drying tunnel, the second drying tunnel and the third drying tunnel is 8m-12m (for example, 8m, 9m, 10m, 11m or 12m).

[0049] This invention also proposes a long-lasting corrosion-resistant GFRP bar with organic-inorganic hybrid synergistic modification in a marine environment. The long-lasting corrosion-resistant GFRP bar with organic-inorganic hybrid synergistic modification in a marine environment in the embodiments of this invention is prepared by the method described above.

[0050] The following detailed embodiments illustrate the organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP reinforcement in marine environments and its preparation method. The main raw materials used in the following embodiments are sourced from: bisphenol A epoxy resin (DGEBA, E51), epoxy value 0.48-0.55 mol / 100g, purchased from Anhui Zhongbo New Materials; methyltetrahydrophthalic anhydride (MeTHPA), 99%, purchased from Maclean; glass fiber, density 2.48 (g / cm³). 3The following reagents were purchased from Zhejiang Jushi: poly(methylhydrosiloxane) (PMHS), average Mn ~390, purchased from Sigma-Aldrich; γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), 98%, purchased from Sigma-Aldrich; the following reagents were purchased from Aladdin Chemistry Co., Ltd: 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), 95%; tetraethyl orthosilicate (TEOS), 98%; carbon nanotubes (CNTs), average diameter 9.5 nm, purity >90%; expandable graphite (EG), average diameter 75 µm, purity >95%; molybdenum disulfide (MoS2), density 4.8 g / cm³. (The tensile strength is 2025 MPa, and the monofilament diameter is 24 µm.) 3 Purity ≥ 99%; Sepiolite (SEP), density 2.2 g / cm³ 3 400 mesh, purity ≥99%.

[0051] Example 1

[0052] The method for preparing organic-inorganic hybrid synergistic modified long-lasting corrosion-resistant GFRP bars in a marine environment according to this embodiment includes the following steps:

[0053] I. GFRP reinforcement is treated with modified epoxy resin; the modified epoxy resin is prepared by a method including the following steps (refer to...). Figure 1 ):

[0054] (1) Carbon nanotubes were pre-dispersed in a mixture of potassium hydroxide solution (concentration: 0.3 mol / L) and ethanol by magnetic stirring (the volume percentage of ethanol in the mixture was 85%). Poly(methylhydrosiloxane) and tetraethyl orthosilicate (CNT:PMHS:TEOS mass ratio 1:5:15, mass ratio of CNT to potassium hydroxide solution and ethanol mixture 1:50) were slowly added. The mixture was then dispersed by ultrasonic and high-speed shearing of three-roll mill (roller gap 10 μm and 5 μm, 10 times each) to obtain uniformly dispersed modified carbon nanotubes (abbreviated as MCNTs).

[0055] (2) Under vacuum, a mixture of tetraethyl orthosilicate and poly(methylhydrosiloxane) in a mass ratio of 3:1 was permeated into the pores of unexpanded graphite (the mass ratio of unexpanded graphite to poly(methylhydrosiloxane) was 1:5). After microwave expansion (800W, 10s), it was dispersed in a mixture of potassium hydroxide solution (0.3mol / L) and ethanol (the volume percentage of ethanol in the mixture was 85%; the mass ratio of unexpanded graphite to the mixture was 1:30). The mixture was heated and stirred, and then mixed evenly by ultrasonic-shear dispersion to obtain modified expanded graphite (abbreviated as MEG).

[0056] (3) Hydrogen-containing silicone oil (PMHS) and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) were mixed in a mass ratio of 1:1, with ethanol as the solvent (mass ratio of ethanol to PMHS was 10:1). The mixture was reacted at room temperature for 8 hours with a magnetic stirrer (200 r / min) under the catalysis of NaOH (mass ratio of NaOH to ethanol was 0.01:1) to obtain organosilicon, which was then stored for later use.

[0057] (4) Under a water bath heating at 60 ℃, the organosilicon (the mass of organosilicon is 5% of the mass of bisphenol A epoxy resin) was physically mixed with bisphenol A epoxy resin (DGEBA) for 10 min to obtain organosilicon epoxy resin; modified carbon nanotubes (the mass of modified carbon nanotubes is 0.03% of the mass of bisphenol A epoxy resin) and modified expanded graphite (the mass of modified expanded graphite is 0.03% of the mass of bisphenol A epoxy resin) were mixed with methyltetrahydrophthalic anhydride curing agent (MeTHPA) to obtain a nanofiller mixture; the organosilicon epoxy resin and the nanofiller mixture were mixed and the mixed solution was stirred evenly by ultrasonic combined with three-roller shear dispersion to obtain modified epoxy resin (abbreviated as M); wherein, the mass ratio of bisphenol A epoxy resin (DGEBA) and methyltetrahydrophthalic anhydride curing agent (MeTHPA) was 100:85.

[0058] The entire modified rebar processing adopts the pultrusion-winding molding process of FRP rebar: This process includes core processes such as yarn feeding, resin impregnation, preforming, curing molding, and traction cutting (all of the above processes can be completed in the corresponding equipment in the existing technology, and will not be described in detail here).

[0059] II. The modified epoxy resin prepared above was placed in a vacuum high-speed stirrer (MSK-SFM-9) and stirred for 24 hours, then poured into an impregnation tank and allowed to stand to remove bubbles.

[0060] III. Arrange the glass fibers on the yarn frame according to the required reinforcing bar diameter, with a fiber volume fraction (the volume fraction here refers to the ratio of the volume occupied by the glass fiber in the FRP reinforcing bar to the total volume of the composite material; used to measure the volume ratio of glass fiber in the composite material) of approximately 80%. Then, using traction force, send the glass fibers to the impregnation tank for impregnation (impregnation rate is 0.8 m / min).

[0061] IV. Add the accelerator (2,4,6-tris(dimethylaminomethyl)phenol accelerator (DMP-30)) to the impregnation tank and mix it evenly with the modified epoxy resin (the mass ratio of accelerator to unmodified epoxy resin is 5:100). Start the temperature control system in the impregnation tank and set the temperature to 50 °C to preheat the modified epoxy resin, giving it a certain degree of fluidity. Under the action of traction, the modified epoxy resin coats the surface of the glass fiber. The glass fiber then passes through a scraper to remove excess resin from its surface. After being sized through forming holes, it is wound around ribs (rib spacing 12 mm).

[0062] V. After the initial forming of the reinforcing material, it enters the curing stage. The curing stage is set with three drying tunnels: the first drying tunnel is for the temperature of the reinforcing material pultrusion die. If the temperature is too high or too low, it will affect the uniformity of resin distribution in the fiber; the second and third drying tunnels are for the curing and post-curing stages of the reinforcing material; the total length of the three drying tunnels is about 10 m, and the distance between each drying tunnel is about 3 m; the drying tunnel temperatures are set to 120 °C, 100 °C, and 100 °C respectively, and the pultrusion rate of the fiber is controlled at 0.8 m / min throughout the process;

[0063] VI. After curing, the reinforcing bar enters the cold air control system, gradually reducing its surface temperature to room temperature. With the help of the pressure system in the traction machine, the formed reinforcing bar is lightly pressed and moved to the cutting system. The reinforcing bar is automatically cut into segments according to the cutting length set in the computer system. The entire cutting process is equipped with a dust removal device to remove debris from the surface of the reinforcing bar, thus obtaining the long-lasting corrosion-resistant GFRP bar with organic-inorganic hybrid synergistic modification in marine environment (abbreviated as M-GFRP) in this embodiment.

[0064] Steps II-VI can be referred to Figure 2 (Steps II-VI are performed in the corresponding equipment in the prior art).

[0065] Example 2

[0066] The only difference between this embodiment and Example 1 is that the quality of the organosilicon in step (4) is different from that in Example 1; all other aspects are the same as in Example 1. Specifically:

[0067] 2-1: In step (4), the mass of the organosilicon is 10% of the mass of the bisphenol A epoxy resin (DGEBA);

[0068] 2-2: In step (4), the mass of the organosilicon is 15% of the mass of the bisphenol A epoxy resin (DGEBA).

[0069] Example 3

[0070] The only difference between this embodiment and Example 1 is that the mass of the modified carbon nanotubes in step (4) is different from that in Example 1; all other aspects are the same as in Example 1. Specifically:

[0071] 3-1: The mass of the modified carbon nanotubes is 0.01% of the mass of bisphenol A epoxy resin (DGEBA);

[0072] 3-2: The mass of the modified carbon nanotubes is 0.05% of the mass of bisphenol A epoxy resin (DGEBA);

[0073] 3-3: The mass of the modified carbon nanotubes is 0.07% of the mass of the bisphenol A epoxy resin (DGEBA).

[0074] Example 4

[0075] The only difference between this embodiment and Embodiment 1 is that the mass of the modified expanded graphite in step (4) is different from that in Embodiment 1; all other aspects are consistent with Embodiment 1. Specifically:

[0076] 4-1: The mass of modified expanded graphite is 0.01% of the mass of bisphenol A epoxy resin (DGEBA);

[0077] 4-2: The mass of modified expanded graphite is 0.05% of the mass of bisphenol A epoxy resin (DGEBA);

[0078] 4-3: The mass of the modified expanded graphite is 0.07% of the mass of the bisphenol A epoxy resin (DGEBA).

[0079] Comparative Example 1

[0080] In this comparative example, pure epoxy resin was used instead of the modified epoxy resin (abbreviated as N) in Example 1.

[0081] The pure epoxy resin in this comparative example was used to prepare GFRP bars, resulting in the GFRP bars of this comparative example (i.e., unmodified GFRP bars; abbreviated as N-GFRP bars).

[0082] Comparative Example 2

[0083] The modified epoxy resin used in this comparative example (the epoxy resin and silicone used in the modified epoxy resins described below are the same as those in Example 1) includes:

[0084] Comparative Example 2-1 (abbreviated as PE-5): The modified epoxy resin is composed of epoxy resin and 5% organosilicon (5% organosilicon means that the mass of organosilicon is 5% of the mass of epoxy resin, the same below).

[0085] Comparative Example 2-2: The modified epoxy resin was made by mixing epoxy resin and 10% organosilicon.

[0086] Comparative Examples 2-3: The modified epoxy resin was made by mixing epoxy resin and 15% organosilicon.

[0087] Comparative Examples 2-4: The modified epoxy resin was made by mixing epoxy resin and 20% organosilicon.

[0088] Comparative Examples 2-4: The modified epoxy resin was made by mixing epoxy resin and 25% organosilicon.

[0089] Comparative Example 3

[0090] The modified epoxy resin in this comparative example (abbreviated as SEP / PE; the epoxy resin and silicone used in the modified epoxy resins described below are the same as those in Example 1) includes:

[0091] Comparative Example 3-1: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon (5% organosilicon means that the mass of organosilicon is 5% of the mass of epoxy resin; the same below) and 0.01% sepiolite (sepiaolite is abbreviated as SEP; 0.01% sepiolite means that the mass of sepiolite is 0.01% of the mass of epoxy resin; the same below).

[0092] Comparative Example 3-2: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.03% sepiolite.

[0093] Comparative Example 3-3: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.05% sepiolite.

[0094] Comparative Examples 3-4: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.07% sepiolite.

[0095] Comparative Example 4

[0096] The modified epoxy resin in this comparative example (abbreviated as MoS2 / PE; the epoxy resin and silicone used in the modified epoxy resins described below are the same as those in Example 1) includes:

[0097] Comparative Example 4-1: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon (5% organosilicon means that the mass of organosilicon is 5% of the mass of epoxy resin; the same below) and 0.01% MoS2 (0.01% MoS2 means that the mass of MoS2 is 0.01% of the mass of epoxy resin; the same below).

[0098] Comparative Example 4-2: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.03% MoS2.

[0099] Comparative Example 4-3: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.05% MoS2.

[0100] Comparative Example 4-4: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.07% MoS2.

[0101] Comparative Example 5

[0102] The modified epoxy resin in this comparative example (abbreviated as CNT / PE; the epoxy resin and silicone used in the modified epoxy resins described below are the same as those in Example 1) includes:

[0103] Comparative Example 5-1: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon (5% organosilicon means that the mass of organosilicon is 5% of the mass of epoxy resin; the same below) and 0.01% carbon nanotubes (0.01% carbon nanotubes means that the mass of carbon nanotubes is 0.01% of the mass of epoxy resin; the same below).

[0104] Comparative Example 5-2: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon and 0.03% carbon nanotubes.

[0105] Comparative Example 5-3: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon and 0.05% carbon nanotubes.

[0106] Comparative Examples 5-4: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon and 0.07% carbon nanotubes.

[0107] Comparative Example 6

[0108] The modified epoxy resin in this comparative example (abbreviated as EG / PE; the epoxy resin and silicone used in the modified epoxy resins described below are the same as those in Example 1) includes:

[0109] Comparative Example 6-1: The modified epoxy resin in this comparative example is composed of epoxy resin, 5% organosilicon (5% organosilicon means that the mass of organosilicon is 5% of the mass of epoxy resin) and 0.01% expanded graphite (0.01% expanded graphite means that the mass of expanded graphite is 0.01% of the mass of epoxy resin).

[0110] Comparative Example 6-2: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.03% expanded graphite.

[0111] Comparative Example 6-3: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.05% expanded graphite.

[0112] Comparative Example 6-4: The modified epoxy resin in this comparative example was composed of epoxy resin, 5% organosilicon and 0.07% expanded graphite.

[0113] Comparative Example 7

[0114] The modified epoxy resin (abbreviated as PE-MCNT) in this comparative example is composed of epoxy resin, 5% organosilicon (both epoxy resin and organosilicon are the same as in Example 1, and the mass of organosilicon is 5% of the mass of epoxy resin) and 0.03% modified carbon nanotubes (the mass of modified carbon nanotubes is 0.01% of the mass of epoxy resin).

[0115] Comparative Example 8

[0116] The modified epoxy resin (abbreviated as PE-MEG) in this comparative example is composed of epoxy resin, 5% organosilicon (both epoxy resin and organosilicon are the same as in Example 1, and the mass of organosilicon is 5% of the mass of epoxy resin) and 0.03% modified expanded graphite (the mass of modified expanded graphite is 0.01% of the mass of epoxy resin).

[0117] Comparative Example 9

[0118] The GFRP reinforcement in this comparative example is commercially available GFRP reinforcement (abbreviated as S-GFRP).

[0119] Experimental example:

[0120] 1. The corrosion resistance of the epoxy resin in Comparative Example 1 and the modified epoxy resin in Comparative Example 2 were tested:

[0121] (1) Surface contact angle test, the test results are as follows Figure 3 As shown:

[0122] Depend on Figure 3 It can be seen that the contact angle of the resin matrix gradually increases with the increase of silicone (PE) content. In particular, when the content is 5 wt.%, the contact angle reaches a maximum of 120.1º, which is 69.87% higher than that of the unmodified pure epoxy resin matrix.

[0123] (2) The epoxy resin matrix of Comparative Example 1 and the modified epoxy resin matrix of Comparative Example 2 were subjected to aging tests in deionized water solution and seawater sand concrete simulated hole solution. The tensile strength was measured and the tensile strength loss rate was calculated. The preparation method of epoxy resin matrix was as follows: First, the epoxy resin was preheated in an oven at 60 ℃ for 10 min. Then, the curing agent MeTHPA was added and mechanically stirred for 20 min. Then, the accelerator (DMP-30) was added (the mass ratio of epoxy resin, curing agent and accelerator was 100:85:5). After thorough stirring, the mixture was placed in a centrifuge and vacuumed for 20 min. The mixture was then poured into a molding mold and finally placed in an oven for high-temperature curing (two-stage curing: 100 ℃ for 1 h; 120 ℃ for 1 h). Finally, the epoxy resin matrix immersion sample was prepared.

[0124] Test method: The ultimate tensile strength was tested after 100 days of exposure in deionized aqueous solution (DW pH=7) and seawater sand concrete simulated hole solution (N-SWSSC alkaline environment pH=13.7); the test results are as follows. Figure 4 As shown:

[0125] Depend on Figure 4 It was found that after 100 days of exposure in deionized aqueous solution (DW pH=7) and simulated pore solution of seawater and sand concrete (N-SWSSC, alkaline environment, pH=13.7), the tensile strength retention rates of the pure epoxy resin matrix were 73.86% and 59.77%, respectively. When the silicone content was 5 wt.%, the modified epoxy resin matrix exhibited the lowest strength loss rates under both corrosive environments, at 7.84% and 14.47%, respectively. Furthermore, the degradation rate of the resin matrix in the simulated alkaline pore solution of concrete was significantly higher than that in the deionized environment at pH=7. Besides water molecules, the presence of alkaline ions further accelerates the deterioration and performance degradation of the resin matrix in FRP reinforcement. The modification with silicone / epoxy resin matrix significantly improved the alkali resistance of the epoxy resin matrix, resulting in better alkali resistance.

[0126] (3) Roughness test:

[0127] Test results as follows Figure 5 As shown; by Figure 5 It can be seen that after corrosion, the surface of the pure epoxy resin matrix (Comparative Example 1) forms uneven corrosion pits. The surface roughness of the sample can be obtained by microscopic 3D morphology images. The average surface roughness Ra is 485, and the root mean square roughness Rq is 710. After adding organosilicon, the surface corrosion of the modified epoxy resin matrix of Comparative Example 2 is significantly slowed down. In particular, when the dosage is 5 wt.%, there is no obvious corrosion on the sample surface, and the roughness is significantly reduced. The Ra and Rq values ​​are reduced to 281 and 430, respectively, which are approximately 42.06% and 39.43%.

[0128] 2. The corrosion resistance of the modified epoxy resins in comparative examples 3-6 was tested:

[0129] (1) The surface contact angle was tested and compared with that of pure epoxy resin in Comparative Example 1; the test results are as follows: Figure 6 As shown:

[0130] Depend on Figure 6 It can be seen that when the CNT content is 0.03 wt.%, the surface contact angle of the CNT / PE modified epoxy resin matrix increases to a maximum of approximately 130°, which is 83.87% higher than that of pure epoxy resin N; compared with single-component organosilicon modification, the contact angle increases by approximately 8.24%. However, when the content is greater than 0.05 wt.%, the contact angle decreases from 130° to 120°. This indicates that when the content is too high (>0.05%), nanomaterial aggregation is likely to occur within the epoxy resin network, thus affecting the surface contact angle of the epoxy resin matrix.

[0131] (2) Tensile strength test:

[0132] Test results are as follows Figure 7 As shown; by Figure 7 It can be seen that the 0.03 wt.% CNT / PE modified epoxy resin matrix exhibits the best tensile properties after corrosion in the N-SWSSC simulated hole solution, with a tensile strength retention rate of 95.21%. In contrast, the strength retention rate of the pure epoxy resin matrix N is 59.76%.

[0133] (3) Corrosion morphology test:

[0134] Test results are as follows Figure 8 As shown; by Figure 8 The figure shows the microstructure of a 0.03 wt.% nanomaterial / organosilicon-modified epoxy resin matrix after 100 days of corrosion in a SWSSC simulated pore solution. In the figure, 0 represents no corrosion and 1 represents corrosion. The figure shows that after corrosion, the pure epoxy resin matrix exhibits water absorption swelling, blistering, and numerous corrosion pits on its surface. After modification with nanomaterials / organosilicon, the corrosion rate of the epoxy resin matrix is ​​slowed down to varying degrees. The CNT / PE-modified epoxy resin matrix shows only a small amount of slight corrosion on its surface. Compared to pure epoxy resin N, its surface roughness decreased from 171 μm to 69 μm, a reduction of approximately 59.64%.

[0135] 4. Corrosion resistance tests of the modified organic resins in Comparative Examples 7-8 and Example 1:

[0136] (1) The microstructure and dispersibility of the unmodified carbon nanotubes, modified carbon nanotubes, expandable graphite, and modified expanded graphite in Example 1 were tested, and the test results are as follows: Figure 9 As shown:

[0137] As shown in (ad) of the figure, before modification, CNTs exhibited irregular agglomerations with a smooth, flat surface and no obvious defects. EDS elemental analysis revealed that carbon (C) was the dominant element. After modification, the closed ends of the CNTs were opened under the activation of KOH, improving the problem of excessive entanglement and agglomeration. The roughness of the modified CNT wall increased significantly, and numerous particles were found attached to both sides of the wall. The elemental distribution showed that the scanned area after CNT modification contained not only carbon (C) but also Si and O elements. Figure 9 (eh). The K element is due to the modification environment being KOH, while Si and O are introduced by the hydrolysis and condensation reaction of PMHS and TEOS.

[0138] As shown in (im) of the figure, unexpanded graphite is lamellar, while after high-temperature microwave expansion, it becomes worm-like, with carbon as its main element. After modification, a large number of white particles were found attached to its surface under a scanning electron microscope. After expansion, a large number of white particles were attached between the lamellar layers. EDS elemental scanning analysis showed that a large number of Si and O elements were attached to the EG surface. Through TEM and diffraction pattern analysis, it can be seen that a large number of spherical particles are interwoven into a network connected to the EG surface and interior after modification. The diffraction pattern is observed to be ring-shaped, which can be inferred to be a polycrystalline diffraction ring. After polycrystalline diffraction ring calibration and crystal comparison, it can be seen that the polycrystalline material is SiO2 crystal, and the SiO2 crystal planes corresponding to the diffraction rings are (111), (220), (311), (222), (120), and (121). This indicates that after EG modification, a large number of silicon films are grafted onto the surface, accompanied by the formation of SiO2 particles, as shown in (nr) of the figure.

[0139] Dispersibility test: 0.03 wt% CNT and 0.03 wt% EG were placed in a mixture of ethanol and water, pre-dispersed by ultrasonication, and then placed in epoxy resin and stirred at low speed (500 rpm, 20 min). The mixture was observed under an electron microscope. Alternatively, CNT and EG were treated with a hydrophobic coating, pre-dispersed in a mixture of ethanol and water (at the same concentration as before modification), placed in epoxy resin, stirred until homogeneous, and then observed under an electron microscope. The results are as follows: Figure 10 As shown in the figure; the test results show that the dispersion uniformity is significantly improved after modification.

[0140] (2) Surface contact angle test, the test results are as follows Figure 11 As shown:

[0141] Test results show that the surface contact angle of the modified epoxy resin matrix (M) used in Example 1 is 142.58°, which is 101.66% higher than that of the pure epoxy resin matrix (N); compared with the PE-MCNT epoxy resin matrix (Comparative Example 7), the surface contact angle of the M matrix is ​​increased by 7.68%; compared with the modified PE-MEG epoxy resin matrix (Comparative Example 8), the surface contact angle of the M matrix is ​​increased by 9.25%. Observation of the wetting behavior of water droplets on the surface of the epoxy resin matrix before and after modification shows that the introduction of Si-O-Si hydrophobic segments and the formation of SiO2 hydrophobic particles increase the surface roughness of the epoxy resin matrix, which is beneficial for water droplets to capture nanoparticle air cushions on the surface of the modified epoxy resin matrix, forming new support points. This significantly reduces the contact area between the water droplets and the resin matrix surface, thus improving the hydrophobic performance.

[0142] (3) Tensile strength test, the test results are as follows Figure 12 As shown:

[0143] Test results show that, without corrosion, the modified epoxy resin matrix M (Example 1) exhibits the highest tensile strength at 81.14 MPa, representing increases of 80.11% and 10.99% compared to N and PE-MCNT epoxy resin matrices (Comparative Example 7), respectively. After 100 days of exposure in DW, the modified epoxy resin matrix M shows the lowest tensile strength loss rate at 0.46%, while pure epoxy resin N experiences a decrease of 26.13%. In the N-SWSSC simulated pore solution, the modified epoxy resin matrix M decreases from 81.14 MPa to 78.17 MPa, a decrease of 3.66%; the tensile strength of the PE-MCNT epoxy resin matrix decreases by 4.78%; and the tensile strength of the pure epoxy resin matrix N decreases by 40.24%. This indicates that grafting CNTs onto the surface of EG with silicon films can effectively improve the corrosion resistance of the epoxy resin matrix, enhance the interfacial bonding between the nanomaterials and the epoxy resin matrix, distribute them more evenly in the epoxy resin, and improve their reinforcing effect on the epoxy resin matrix.

[0144] (4) Interlaminar shear strength test, the test results are as follows Figure 13 As shown:

[0145] Test results show that, without corrosion, the interlaminar shear strength of the modified epoxy resin matrix M (Example 1) is 122.40 MPa, which is an increase of 63.63% and 10.46% compared to pure epoxy resin N and PE-MCNT epoxy resin matrix (Comparative Example 7), respectively. After 100 days of exposure in DW, the interlaminar shear strength of the modified epoxy resin matrix M, PE-MCNT epoxy resin matrix, and pure epoxy resin matrix N decreased by 6.86%, 10.99%, and 36.89%, respectively. A similar trend was observed in N-SWSSC solution, with the interlaminar shear strength retention rates of the three being approximately 87.58%, 81.56%, and 53.75%, respectively. This phenomenon indicates that the mechanical properties and corrosion resistance of the surface-modified nanomaterial / organosilicon hybrid modified epoxy resin matrix are improved. The introduction of Si-O segments gives the entire polymer chain good flexibility and is beneficial to the rotation of the molecular chain after curing. Therefore, under external loads, the introduced chain segments can dissipate energy and relieve some stress, thereby improving the mechanical properties of the material. Furthermore, the grafting of nanomaterial silicon films gives the epoxy resin matrix surface excellent hydrophobic properties, which can delay or reduce the water absorption rate of the resin matrix, hindering or slowing down the swelling and plasticization of the resin matrix, thus slowing down the corrosion rate of the epoxy resin matrix.

[0146] (5) Fracture surface morphology test, the test results are as follows Figure 14 As shown:

[0147] Corrosion Resistance Mechanism Analysis: The fracture surface of pure resin matrix is ​​relatively smooth, and the tear surface is relatively flat, belonging to brittle fracture surface. When pure epoxy resin is subjected to external force, cracks tend to propagate rapidly, leading to rapid material fracture and exhibiting brittle texture. The fracture surface of silicone PE / epoxy resin shows a more complex crack path, with cracks forming numerous branches and tortuosities within the material. Similarly, the introduction of modified carbon nanotubes increases the mechanical strength and modulus of epoxy resin. During crack propagation, the carbon nanotubes hinder the cracks, making the crack path more complex, thereby absorbing more energy and improving the toughness of the material. Likewise, the incorporation of modified EG causes the epoxy matrix to encounter more obstacles during crack propagation, forming complex crack paths. Complex crack paths can absorb and disperse more energy, thereby improving the toughness of the material. The fracture surface of MCNTs / MEG / PE modified epoxy resin (Example 1, modified epoxy resin M) shows a very complex crack path, with cracks forming numerous branches and tortuosities within the material. Modified multi-walled carbon nanotubes and expanded graphite exhibit better dispersibility, leading to increased resistance to crack propagation by the nanofillers and a more complex crack path. The introduction of flexible silicone PE segments further improves the flexibility and internal stress distribution of epoxy resin. The increased resistance to crack propagation and the more complex crack path result in greater energy absorption and a significant improvement in material toughness. The synergistic effect of these two modified nanomaterials with silicone significantly enhances the toughness of epoxy resin, resulting in a highly complex crack path and demonstrating excellent toughness.

[0148] (6) Corrosion morphology test, the test results are as follows Figure 15 As shown:

[0149] As shown in the corrosion morphology diagrams, after corrosion in a highly alkaline environment, pure epoxy resin exhibits numerous pores and depressions, indicating severe corrosion and high surface roughness. The PE / epoxy resin matrix (Comparative Example 2-1) shows reduced surface corrosion, but still exhibits large areas of swelling and corrosion pits. The PE-MCNT epoxy resin matrix (Comparative Example 7) shows localized swelling and small-area corrosion pits, accompanied by the formation of corrosion products. The PE-MEG epoxy resin matrix (Comparative Example 8) shows localized swelling and plasticization, with a small number of corrosion micropores forming on the surface. The MCNTs / MEG / PE modified epoxy resin matrix (Example 1) shows significantly reduced surface corrosion, with almost no obvious pores or cracks; only some corrosion ion crystals adhere to the matrix surface, indicating that its corrosion resistance is significantly superior to the other materials. This demonstrates the excellent synergistic effect of the three materials, effectively mitigating the erosion rate of corrosion ions. It possesses superior alkali resistance and is suitable for extreme and harsh environments such as marine environments and saline soil areas.

[0150] 5. GFRP rib performance test:

[0151] (1) Tensile strength test: The tensile strength test results of the GFRP bars (S-GFRP) of Example 1 (M-GFRP), Comparative Example 1 (N-GFRP) and Comparative Example 9 are as follows: Figure 16 As shown:

[0152] Test results show that, without corrosion, the average ultimate loads of N-GFRP (unmodified GFRP bars), M-GFRP (modified GFRP bars), and S-GFRP (commercially available GFRP bars) are 83.22 kN, 95.06 kN, and 81.43 kN, respectively. Compared to N-GFRP and S-GFRP, the ultimate load increase of M-GFRP is approximately 14.28% and 16.73%, respectively. After 30 days of corrosion, the retention rates of N-GFRP, M-GFRP, and S-GFRP are 92.71%, 93.28%, and 92.37%, respectively, with little difference in strength loss rates among the three. However, after 90 days of corrosion, the magnitude of tensile strength loss increases, with N-GFRP, M-GFRP, and S-GFRP decreasing by 24.91%, 18.40%, and 31.60%, respectively. The rate of decrease for M-GFRP is lower than that for N-GFRP and S-GFRP. As the corrosion time increased to 120 days, the ultimate load values ​​of N-GFRP, M-GFRP, and S-GFRP decreased to 55.63 kN, 76.05 kN, and 48.78 kN, respectively. Compared with N-GFRP and S-GFRP, the load value of M-GFRP increased by approximately 36.77% and 55.90%. At this point, the retention rates of N-GFRP, M-GFRP, and S-GFRP reinforcement were 66.84%, 80.00%, and 59.90%, respectively. This indicates that the corrosion-resistant modification of the resin matrix effectively mitigated the degradation rate of the reinforcement.

[0153] (2) Destruction mode test:

[0154] The tensile failure mode test results of the GFRP bars (S-GFRP) of Example 1 (M-GFRP), Comparative Example 1 (N-GFRP), and Comparative Example 9 are as follows: Figure 17 As shown:

[0155] Test Results: In the absence of corrosion, the failure mode was a combination of bursting and splitting. The internal fibers of the reinforcement primarily exhibited bursting failure, while the outer fibers showed splitting failure. There were no significant differences in the failure modes among the three types of reinforcement. However, the bursting of internal fibers in M-GFRP was more uniform and covered a larger area, while N-GFRP and S-GFRP mostly showed splitting failure. After 60 days of corrosion, the failure modes changed significantly. M-GFRP retained the bursting mode, while the failure modes of N-GFRP and S-GFRP evolved into pull-out failure. During the pull-out process, all three types of reinforcement emitted cracking sounds. The formation of cracks in M-GFRP was a gradual process; the initial splitting sound was slow, the crack gradually developed, and then the frequency of the sound gradually increased, culminating in a loud crack as the sample broke. However, the pull-out failure of S-GFRP did not produce a prolonged sound; the fracture sound changed from brittle to deep. As the corrosion age increased to 120 days, the modified M-GFRP reinforcement still exhibited burst failure, while the S-GFRP and N-GFRP reinforcements showed direct pull-out failure. This indicates that the modified matrix and fibers maintain good adhesion under the corrosive effects of corrosive ions. The matrix modification enhances the corrosion resistance of the reinforcement, and under external loads, the fibers and matrix effectively transfer the load, resulting in uniform stress distribution throughout the reinforcement and thus effectively mitigating the rate of mechanical property loss.

[0156] (3) Interlaminar shear strength test

[0157] The tensile strength test results of the GFRP bars (S-GFRP) of Example 1 (M-GFRP), Comparative Example 1 (N-GFRP), and Comparative Example 9 (S-GFRP) are shown in Table 1 below:

[0158] Table 1. Interlaminar shear properties of reinforcing bars at different corrosion ages.

[0159]

[0160] As shown in the table above, before corrosion, the shear load value of M-GFRP increased by 8.81% and 24.90% compared to N-GFRP and S-GFRP, respectively. The ultimate load value gradually decreased with increasing exposure time. After 30 days of corrosion, the interlaminar shear strength of N, M, and S-GFRP decreased by 11.19%, 6.55%, and 24.91%, respectively. As the corrosion age increased to 120 days, the decrease in strength of N-GFRP, M-GFRP, and S-GFRP increased, decreasing to 17.14 MPa, 20.80 MPa, and 10.18 MPa, respectively, with retention rates of 68.47%, 76.32%, and 46.69%. The ultimate load value of M-GFRP increased by approximately 21.28% compared to N-GFRP and was about twice that of S-GFRP. In terms of the rate of performance degradation, the modified reinforcement material M-GFRP was superior to N-GFRP and S-GFRP.

[0161] (3) Failure modes of GFRP reinforcement in interlaminar shear test as follows Figure 18 As shown:

[0162] As shown in the figure, when the sample is uncorroded, under external shear force, the bonding force between the internal layers is insufficient to resist the shear force. The fiber / matrix interface becomes the starting point for reinforcement failure, generating microcracks between the layers. With the continued action of shear force, the microcracks gradually expand, forming through cracks along the neutral axis. The appearance of horizontal cracks in the planar plane during the shear test indicates good bonding performance at the fiber / resin interface.

[0163] For corroded GFRP reinforcement bars, after 30 days of corrosion, numerous radial microcracks formed on the fracture surface of the sample, and the location of transverse through-cracks was no longer fixed. This phenomenon indicates that the stress distribution inside the material is uneven, and under shear force, a complex stress state is generated inside the reinforcement bar. This stress state may cause cracks to propagate in different directions, forming radial cracks. In addition, the decrease in fiber / resin interfacial bonding performance makes it easier for slippage to occur between the fiber and the matrix, thereby changing the failure morphology. As the corrosion age increased to 120 days, the cracks on the sample fracture surface deepened, and the reinforcement bar was completely crushed, exhibiting a loose state after crushing. Both N / S-GFRP and M-GFRP underwent severe corrosion, while the failure mode of M-GFRP remained through-crack failure, indicating that the matrix modification process enhanced the interfacial bonding force between the fiber and the matrix, making it difficult for the fiber and the matrix to slip under external load, thus making it less prone to radial crack formation.

[0164] (4) The cross-sectional morphology of the GFRP rebar after 120 days of corrosion is as follows: Figure 19 As shown:

[0165] As shown in the figure, for N-GFRP, when exposed to a corrosive environment, a large amount of matrix is ​​damaged and significantly degraded, which affects the interfacial adhesion between the fiber and the matrix, making the fibers prone to breakage or detachment, thus reducing the interlaminar shear strength of the GFRP tendons. In M-GFRP, the introduction of silicon-modified CNTs, expanded graphite, and organosilicon improves the corrosion resistance of the GFRP tendons. Organosilicon has good weather resistance and oxidation resistance, preventing the degradation of epoxy groups in harsh environments. Simultaneously, the addition of silicon-modified CNTs and expanded graphite enhances the interfacial adhesion between the matrix and the fibers, allowing the matrix to better disperse stress under load, reducing crack formation, and preventing fiber breakage or detachment. S-GFRP exhibits the highest degree of corrosion at the cross-section, with significant resin breakage, fiber / resin interface debonding, and accompanying fiber etching.

[0166] (5) The interfacial bond performance of seawater sand concrete / GFRP reinforcement is as follows: Figure 20 As shown:

[0167] As shown in the figure, the bond strength between the GFRP reinforcement and the concrete interface initially increases and then decreases with increasing corrosion age. Comparing the three types of reinforcement, before corrosion, the bond strength of the M-GFRP reinforcement / concrete interface increased by 16.20% and 25.94% compared to the N / S-GFRP reinforcement, respectively. After 120 days of corrosion, the bond strength retention rates of the N / M / S-GFRP reinforcement and the concrete interface were 87.01%, 103.72%, and 85.02%, respectively, with the M-GFRP reinforcement / concrete interface bond strength being approximately 38.51% and 53.63% higher than that of the N / S-GFRP reinforcement. With increasing corrosion age, the increase in bond strength between the M-GFRP reinforcement and the concrete interface gradually increased compared to the S-GFRP reinforcement, rising from 32.21% at 60 days to 53.63% at 120 days. This indicates that epoxy resin modification can effectively delay the degradation rate and extent of the bond strength degradation between the GFRP reinforcement and the concrete. Modified GFRP bars have a strong ability to work together with concrete.

[0168] (6) Microscopic morphology of the fracture surface of GFRP tendons at different corrosion ages, such as Figure 21 As shown:

[0169] As shown in the figures, the fiber / resin interface of the unexposed GFRP reinforcement is intact. The resin matrix surface shows no obvious damage, with only a small amount of resin fragments adhering to the reinforcement after breakage. The resin matrix surface of the S-GFRP reinforcement has tiny pores. When porous reinforcement is exposed to a corrosive environment, corrosive ions can enter the resin matrix through these pores, accelerating the corrosion rate. This is a significant factor contributing to the high rate of mechanical property loss in S-GFRP reinforcement. After 30 days of exposure, almost no obvious corrosion was observed on the cross-section of the M-GFRP reinforcement. However, some cracks and resin matrix fractures appeared on the matrix surface of the N-GFRP reinforcement, and localized areas of the S-GFRP reinforcement showed fiber / resin interface debonding and resin matrix fracture. After 90 days of exposure, severe resin corrosion and large-area pitting corrosion occurred in most areas of the N-GFRP reinforcement, exposing the fibers on the surface. On the cross-section of the S-GFRP reinforcement, a large amount of resin was corroded, a large amount of fiber was exposed, and there was some etching. In comparison, M-GFRP reinforcement exhibited less corrosion and better fiber / resin interface adhesion than the other two types. After 120 days of exposure, significant fiber exposure and fiber / resin interface debonding led to a substantial decrease in the mechanical properties of N and S-GFRP reinforcements, while M-GFRP reinforcement showed only slight corrosion. The reasons for this are: CNTs and EG, as reinforcing fillers, effectively dispersed external loads and delayed crack propagation when added to the resin matrix of the GFRP reinforcement; the surface modification properties of the silicone film improved the interfacial compatibility between CNT / EG and the epoxy resin matrix, enhancing the adhesion between nanomaterials and epoxy resin; and the hydrophobic and acid / alkali resistant properties of silicone slowed down the degradation rate of the epoxy resin matrix in harsh environments.

[0170] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing long-lasting corrosion-resistant GFRP bars with organic-inorganic hybrid synergistic modification in a marine environment, characterized in that, Includes the following steps: I. GFRP reinforcement is treated with modified epoxy resin; The modified epoxy resin is prepared by a method comprising the following steps: (1) Carbon nanotubes were pre-dispersed in a first alkaline solution, and poly(methylhydrosiloxane) and tetraethyl orthosilicate were added and dispersed to obtain uniformly dispersed modified carbon nanotubes. (2) Under vacuum, poly(methylhydrosiloxane) and tetraethyl orthosilicate are mixed with expandable graphite, microwave expanded and then dispersed in a second alkaline solution to obtain modified expanded graphite. (3) Mix hydrogen-containing silicone oil with γ-(2,3-epoxypropoxy)propyltrimethoxysilane and react at room temperature under alkaline catalysis to obtain organosilicon; (4) Heating the epoxy resin, adding the organosilicon, stirring, to obtain organosilicon epoxy resin; mixing the modified carbon nanotubes and modified expanded graphite with the curing agent evenly to obtain a nanofiller mixture; mixing the organosilicon epoxy resin with the nanofiller mixture to obtain the modified epoxy resin. In steps (1) and (2), the mass ratio of poly(methylhydrosiloxane) to tetraethyl orthosilicate is 1:1-1:4; In step (3), the mass ratio of hydrogen-containing silicone oil to γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 1:0.5-1:3; the reaction time at room temperature is 4-8 hours.

2. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 1, characterized in that, The mass of the silicone is 5%-15% of the mass of the epoxy resin; The mass of the carbon nanotubes or expandable graphite is 0.01%-0.07% of the mass of the epoxy resin.

3. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 1, characterized in that, The mass ratio of the carbon nanotubes and / or expandable graphite to the poly(methylhydrosiloxane) is 1:5-1:10; The first alkaline solution and / or the second alkaline solution are a mixed solution of potassium hydroxide and ethanol.

4. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 2, characterized in that, In step (2), the power of the microwave is 600-1000W and the duration of the microwave is 5-15s.

5. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 1, characterized in that, The base in step (3) is sodium hydroxide, and the solvent is ethanol.

6. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 1, characterized in that, In step (4), the mass ratio of the epoxy resin to the curing agent is 100:(70-90); After heating to 60-80℃, add the organosilicon and stir for 10-30 minutes.

7. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 1, characterized in that, It also includes the following steps: II. Stir the modified epoxy resin, transfer it to the impregnation tank, and let it stand to remove bubbles; III. Arrange the glass fiber on the yarn feeding frame and transport it to the impregnation tank for impregnation. IV. Add accelerator and modified epoxy resin to the impregnation tank and mix evenly. Preheat the modified epoxy resin in the impregnation tank. The glass fiber is impregnated with resin and sized through forming holes before being wound around ribs to obtain the preliminary rib material. V. Allow the pre-formed reinforcing material to enter the curing stage for curing; VI. Cool, press, and cut the cured reinforcing material.

8. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 7, characterized in that, In step IV, the curing includes preliminary curing and secondary curing; The initial curing temperature is 100-140℃; The secondary curing process is carried out in two stages, maintaining a constant temperature of 80-120℃.

9. The preparation method of organic-inorganic hybrid synergistic modification long-lasting corrosion-resistant GFRP bar in a marine environment as described in claim 7, characterized in that, In step II, the impregnation rate is 0.6-1.0 m / min; In step III, the preheating temperature is 40-60℃; In step IV, the material is cured after passing through the first drying tunnel, the second drying tunnel, and the third drying tunnel in sequence. The temperature of the first drying tunnel is 100-140℃, and the temperatures of the second and third drying tunnels are 80-120℃, respectively. During the curing process, the pultrusion rate of the reinforcing material is 0.8-1.2m / min, and the total length of the first, second, and third drying tunnels is 8-12m.

10. A long-lasting corrosion-resistant GFRP rebar with organic-inorganic hybrid synergistic modification for marine environments, characterized in that... The organic-inorganic hybrid synergistic modification of long-lasting corrosion-resistant GFRP bars in the marine environment is prepared by the method described in any one of claims 1-9.

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