A Method for Enhancing Interface Bonding and Corrosion Resistance of Basalt Fiber Composites

Abstract

The present invention provides a method for enhancing the interfacial bonding and corrosion resistance of basalt fiber composites, belonging to the field of chemical methods for fiber surface modification. This method is achieved through the following steps: First, the basalt fiber is treated by high-temperature reflux with an organic solvent to obtain desized basalt fiber; then, the desized basalt fiber is immersed in a dopamine solution for self-polymerization to obtain basalt fiber with a polydopamine coating; the basalt fiber with a polydopamine coating is successively immersed in a zinc salt solution and a 2-methylimidazole solution to obtain basalt fiber modified with ZIF-8; finally, the basalt fiber modified with ZIF-8 and the resin are mixed by electrostatic coating and then formed by a segmented hot pressing method to obtain a basalt fiber composite material; through this method, a composite structure composed of the synergistic effect of the dopamine self-polymerization layer and ZIF-8 is introduced on the surface of the basalt fiber, greatly enhancing the interfacial bonding force between the fiber and the resin and the corrosion resistance of the composite material.

Description

Technical Field

[0001] The present invention belongs to the field of fiber surface modification chemistry, and particularly relates to a method for enhancing the interfacial bonding and corrosion resistance of basalt fiber composites. Background Art

[0002] As a new type of high-performance fiber, basalt fiber (BF) has gradually replaced glass fiber and carbon fiber in many engineering fields due to its excellent mechanical properties, high temperature resistance, acid and alkali resistance, and good corrosion resistance, becoming an important choice for future composites. However, when basalt fiber binds to the resin matrix, due to its low surface energy and poor hydrophilicity, the interfacial bonding strength between it and the resin matrix is low, thus affecting the overall mechanical properties and durability of the composite material. Therefore, how to improve the interfacial bonding force and corrosion resistance between basalt fiber and resin matrix through surface modification has become an important research direction.

[0003] The surface of basalt fiber is smooth and chemically inert, resulting in poor bonding with the matrix material, which is not conducive to the stress transfer from the matrix to the fiber, thus limiting the effective reinforcement of basalt fiber. Currently, common fiber surface modification methods include physical methods (such as plasma treatment, spraying method) and chemical methods (such as surface solvent treatment, chemical impregnation method, etc.). Although these methods can improve the surface properties of the fiber to a certain extent, there are still some limitations, such as complex treatment processes, unstable effects, or poor environmental adaptability. Therefore, it is of great theoretical and practical significance to develop a modification method that is efficient, simple, environmentally friendly, and can significantly improve the interfacial bonding and corrosion resistance of basalt fiber composites.

[0004] Therefore, the present invention proposes a method for modifying basalt fiber by compounding dopamine and ZIF-8. By successively desizing, self-polymerizing polydopamine, impregnating with zinc salt and 2-methylimidazole solution to generate ZIF-8 material on the surface of basalt fiber (BF), and finally hot pressing with epoxy resin, the interfacial bonding strength between basalt fiber and resin matrix is significantly enhanced, and it shows more excellent corrosion resistance in a corrosive environment. This modification method is not only simple and efficient, but also environmentally friendly and has high application prospects, which is of great significance for enhancing the long-term durability and engineering safety of composites. Summary of the Invention

[0005] The purpose of the present invention is to effectively solve the defects of the chemical inertness of the basalt fiber surface and the weak interfacial interaction between it and the resin matrix, improve the bonding strength between the basalt fiber surface and the resin matrix, and enhance the corrosion resistance of basalt fiber composites, and provide a method for enhancing the interfacial bonding and corrosion resistance of basalt fiber composites.

[0006] The technical solution provided by the present invention to solve the above technical problems is as follows: A method for enhancing the interfacial bonding and corrosion resistance of basalt fiber composites, comprising the following steps:

[0007] S1. After the basalt fibers are put into an organic solvent and refluxed at high temperature, they are washed and dried to obtain desized basalt fibers. Subsequently, tris(hydroxymethyl)aminomethane buffer solution is added to the dopamine hydrochloride solution and the pH is adjusted to 8.5. After ultrasonic dispersion, the desized basalt fibers are immersed therein, reacted, washed, and dried to obtain basalt fibers with a polydopamine coating;

[0008] S2. The basalt fibers with a polydopamine coating obtained in S1 are immersed in a zinc salt solution for low-temperature reaction, washed, and dried to obtain basalt fibers soaked with zinc salt;

[0009] S3. The basalt fibers soaked with zinc salt obtained in S2 are further immersed in a 2-methylimidazole solution, reacted at a constant temperature, washed, and dried to obtain basalt fibers modified with ZIF-8;

[0010] S4. Epoxy resin and a curing agent are mixed and stirred, and then a catalyst is added. After vacuum degassing, it is reserved for use;

[0011] S5. The mixture of the resin and the curing agent obtained in S4 is electrostatically coated onto the surface of the basalt fibers modified with ZIF-8 obtained in S3. Then, the electrostatically coated basalt fibers are laid on a mold, and a basalt fiber composite is obtained by segmented hot pressing.

[0012] A further technical solution is that in the step S1, the organic solvent is acetone and ethyl acetate, and the volume ratio is 3:1; the mass ratio of the desized basalt fibers to the dopamine solution is 1:50, the reaction temperature is 40°C, the stirring speed is 500 rpm, the reaction time is 8 hours, and the polydopamine coverage rate reaches more than 80%.

[0013] A further technical solution is that in the step S2, the solute of the zinc salt solution is zinc nitrate hexahydrate, the solvent is methanol, the concentration is 0.15 - 0.3 mol / L, the stirring speed is 300 rpm, the stirring time is 1 hour, the stirring temperature is 40°C, the soaking reaction time is 6 - 9 hours, the soaking reaction temperature is 5°C - 10°C, the whisker length is 100 - 300 nm, the diameter is 20 - 50 nm, and the surface roughness Ra of the whiskers is 50 - 80 nm.

[0014] A further technical solution is that in the step S3, the solute of the 2-methylimidazole solution is 2-methylimidazole, the solvent is a methanol solution, the concentration is 0.2 - 0.4 mol / L, the stirring speed is 300 rpm, the stirring time is 1 hour, the soaking reaction time is 6 - 9 hours, and the reaction temperature is 50°C.

[0015] Furthermore, in step S3, the crystal particle size of the ZIF-8 is 50 - 200 nm; the molar ratio of zinc ions (Zn²⁺) to 2-methylimidazole is 1:1.5 - 1:2.5; the thickness of the ZIF-8 modification layer is 2 - 5 μm, the surface roughness of the ZIF-8 modified basalt fiber is 0.3 - 0.5 μm, the pH value is 5.5 - 6.0, and the ZIF-8 coverage rate reaches 90%.

[0016] A further technical solution is that the epoxy resin in step S4 is E51 epoxy resin, the catalyst is calcium oxide (CaO), the curing agent is methyltetrahydrophthalic anhydride, the mass ratio of the epoxy resin to the curing agent is 10:8, and the mass ratio of calcium oxide (CaO) to the total mass of the epoxy resin and the curing agent is 0.1 - 0.5%;

[0017] Furthermore, in step S4, the stirring speed is 300 rpm, the stirring temperature is 35°C, and the stirring time is 30 minutes; the vacuum degassing is divided into two steps. The first step has a vacuum degree of 10 MPa and a time of 10 - 15 minutes, and the second step has a vacuum degree of 5 MPa and a time of 5 - 10 minutes.

[0018] A further technical solution is that in step S5, the coating viscosity of the electrostatic coating technology should be controlled at 150 - 250 mPa·s (measured at 25°C), the electrostatic voltage of the spray gun is 20 - 30 kV, the coating thickness is controlled at 50 - 70 μm, the distance between the spray gun and the surface of the basalt fiber should be 15 - 25 cm, the spraying air pressure is set at 0.2 - 0.5 MPa, the coating temperature should be 25 - 35°C, and the humidity of the electrostatic coating is 40 - 60%.

[0019] Furthermore, in step S5, the basalt fibers are laid on the mold in an alternating manner with the intersection angles between each layer being 15° / 60° and 60° / 90°.

[0020] Furthermore, in step S5, the segmented hot pressing method is divided into three stages. The first stage is the pre-curing stage, with a pressure of 0.5 MPa, a temperature of 80°C, and a time of 30 minutes; the second stage is the heating and pressure increasing stage. The pressure is first increased to 2 MPa and the temperature is increased to 120°C, then the pressure is increased to 5 MPa and the temperature is increased to 150°C, and both pressure increases are maintained for 1 hour; the third stage is the cooling and constant pressure stage, with a pressure of 5 MPa and the process ends when the temperature reaches room temperature. The porosity of the composite material interface is ≤0.5%, and the pore size is ≤5 μm.

[0021] The second technical problem to be solved by the present invention is to provide a basalt fiber composite material that enhances the interface and corrosion resistance of the basalt fiber composite material prepared by the above method.

[0022] The present invention has the following beneficial effects:

[0023] (1) Through an innovative approach that combines dopamine self-polymerization and modification with metal-organic framework (ZIF-8), the present invention utilizes the strong adhesion of polydopamine and the chelation between polydopamine and zinc ions (Zn²⁺) to synergistically enable the in-situ growth of ZIF-8 on the surface of basalt fibers, forming a dual-interface enhancement structure of chemical bonding and nano-scale mechanical interlocking. This modification method significantly improves the interfacial bonding force between basalt fibers and epoxy resin, and enhances the mechanical properties of the composite material, especially its mechanical stability in corrosive environments.

[0024] (2) Traditional fiber-reinforced composite materials often fail rapidly in harsh environments due to insufficient corrosion resistance. However, the present invention utilizes the anti-corrosion characteristics of ZIF-8 and successfully introduces it to the surface of basalt fibers through the chemical bonding between polydopamine and zinc ions (Zn²⁺) and the mechanical interlocking between polydopamine and ZIF-8. While improving the interfacial bonding force of the material, the corrosion resistance of the composite material is enhanced. Especially in corrosive environments such as seawater, the durability of the composite material is greatly improved, extending its service life.

[0025] (3) The modified materials (such as dopamine, ZIF-8, etc.) used in the present invention have good compatibility with basalt fibers. They not only do not affect the original properties of the fibers but also enhance their functional performance in the composite material. Different from traditional fiber-reinforced composite materials, the composite material modified by this method has enhanced mechanical properties, corrosion resistance, and durability, meeting the requirements of modern engineering materials for high performance. Description of the Drawings

[0026] Figure 1 is the preparation flow chart of the present invention;

[0027] Figure 2 is the scanning electron microscope image of desized basalt fibers;

[0028] Figure 3 is the scanning electron microscope image of ZIF8-modified basalt fibers;

[0029] Figure 4 is the single-filament tensile strength diagram of basalt fibers with or without dopamine-assisted ZIF-8 modification;

[0030] Figure 5 is the interfacial shear strength diagram of basalt fibers with or without dopamine-assisted ZIF-8 modification;

[0031] Figure 6 is the atomic force microscope image of the surface of basalt fibers before and after ZIF-8 modification;

[0032] Figure 7 Interface shear strength diagram of basalt fibers modified with different concentrations of ZIF-8;

[0033] Figure 8 Flexural strength diagram of basalt fiber composites before and after ZIF-8 modification;

[0034] Figure 9 Flexural strength retention diagram of basalt fiber composites before and after ZIF-8 modification under seawater corrosion; Specific implementation manners

[0035] The present invention will be further described below in conjunction with embodiments and the accompanying drawings.

[0036] Embodiment 1

[0037] As Figure 1 shown, a method for enhancing the interfacial bonding and corrosion resistance of basalt fiber composites provided by the present invention is prepared through the following steps:

[0038] S1. The basalt fibers are put into an organic solvent of acetone and ethyl acetate with a volume ratio of 3:1 for high-temperature reflux to obtain desized basalt fibers. Subsequently, tris(hydroxymethyl)aminomethane buffer solution is added to the dopamine hydrochloride solution and the pH is adjusted to 8.5. Then, dopamine self-polymerization is carried out according to the mass ratio of desized basalt fibers to dopamine solution of 1:50. The reaction time is 8 hours, the reaction temperature is 40°C, the stirring speed is 500 rpm, and after ultrasonic dispersion, washing and drying are carried out to obtain basalt fibers with a dopamine coating;

[0039] S2. The basalt fibers with a polydopamine coating prepared in S1 are immersed in a zinc salt solution with a concentration of 0.2 mol / L for 8 hours, and the reaction temperature is 8°C. The solute of the zinc salt solution is zinc nitrate hexahydrate, and the solvent is methanol. When preparing, it is maintained at 40°C and a stirring speed of 300 rpm for 1 hour. After the reaction, washing and drying are carried out to obtain basalt fibers soaked with zinc salt;

[0040] S3. The basalt fibers soaked with zinc salt prepared in S2 are further immersed in a 2-methylimidazole solution with a concentration of 0.3 mol / L, and the reaction is carried out at a constant temperature of 50°C for 8 hours. The solute of the 2-methylimidazole solution is 2-methylimidazole, and the solvent is methanol. When preparing, it is maintained at a stirring speed of 300 rpm for 1 hour. After the reaction, washing and drying are carried out to obtain basalt fibers modified with ZIF-8;

[0041] S4. Mix E51 epoxy resin and the curing agent methyltetrahydrophthalic anhydride in a mass ratio of 10:8, stir them, and then add calcium oxide (CaO) with a mass of 0.3% of the total mass of the epoxy resin and the curing agent. Then stir at a temperature of 35 °C and a stirring speed of 300 rpm for 30 minutes, then keep it at a vacuum degree of 10 MPa for 10 minutes, and finally keep it at a vacuum degree of 5 MPa for 5 minutes and set aside for later use;

[0042] S5. Apply the resin and curing agent mixture prepared in S4 to the surface of the ZIF-8 modified basalt fiber prepared in S3 by electrostatic coating. The viscosity of the electrostatic coating is 200 mPa·s (measured at 25 °C), the electrostatic voltage of the spray gun is 25 kV, the coating thickness is 55 μm, the distance between the spray gun and the basalt fiber surface is 18 cm, the spraying gas pressure is 0.3 MPa, the coating temperature is 25 °C, the humidity of the electrostatic coating is 50%, and the basalt fibers are laid on the mold at alternating angles of 15° / 60° and 60° / 90°. Then obtain the basalt fiber composite material by segmented hot pressing. The hot pressing is divided into three stages. The first stage is the pre-curing stage, with a pressure of 0.5 MPa, a temperature of 80 °C, and a time of 30 minutes; the second stage is the heating and pressure increasing stage. The pressure is first increased to 2 MPa and the temperature is increased to 120 °C. Then the pressure is increased to 5 MPa and the temperature is increased to 150 °C. Both pressure increases are maintained for 1 hour; the third stage is the cooling and constant pressure stage, with a pressure of 5 MPa and the process ends when the temperature reaches room temperature.

[0043] The surface morphology of the desized basalt fiber is as Figure 2 shown, with a smooth and flat surface. The surface morphology of the ZIF-8 modified basalt fiber is as Figure 3 and the surface roughness is as Figure 4 shown. A metal-organic framework structure of ZIF-8 is formed on the surface of the ZIF-8 modified basalt fiber, and the surface roughness reaches 0.38 μm.

[0044] Comparative Example 1

[0045] Compared with Example 1, in S1, the desized basalt fiber (named BF), the ZIF-8 basalt fiber directly grown without dopamine treatment (named BF@ZIF-8), and the ZIF-8 basalt fiber grown after dopamine treatment (named BF-PDA@ZIF-8) were used to conduct fiber single filament tensile strength tests as Figure 5 shown and micro-droplet debonding tests as Figure 6As shown in the figure, the single-filament tensile strength of basalt fibers treated with dopamine and then modified (named BF-PDA@ZIF-8) is 15% higher than that of basalt fibers directly modified without dopamine treatment (named BF-PDA@ZIF-8), indicating that the active groups on the surface of polydopamine provide growth sites for the growth of ZIF-8. Physically, the adhesion of polydopamine makes ZIF-8 bind more tightly to the surface of basalt fibers.

[0046] Comparative Example 2

[0047] Compared with Example 1, in S3, the concentration ratios of zinc salt solution to 2-methylimidazole solution were changed to 1:1.5 (named BF-PDA@ZIF-8-1.5), 1:2 (named BF-PDA@ZIF-8-2), and 1:2.5 (named BF-PDA@ZIF-8-2.5) respectively, to explore the influence of the concentration ratio of metal ions and organic ligands in the metal-organic framework on the interface modification of basalt fibers. Micro-droplet debonding tests were carried out on the three modified basalt fibers, and the results are as Figure 7 shown, which are 58.7 Mpa, 59.5 Mpa, and 59 Mpa respectively. The strengths of the three modified basalt fibers are not very different, and the size of the concentration of the two modified solutions has no significant influence on the modification effect.

[0048] In order to further verify the enhancement of the interfacial bonding of ZIF-8 modified basalt fiber composites, basalt fiber reinforced epoxy composites were prepared, and bending tests were carried out on basalt fiber reinforced epoxy composites before ZIF-8 modification (named BF / EP) and basalt fiber reinforced epoxy composites after ZIF-8 modification (named BF-PDA@ZIF-8 / EP). The test results are as Figure 8 shown.

[0049] Comparative Example 3

[0050] In order to verify the corrosion resistance of the modified basalt fiber composites, unmodified basalt fiber composites (named BF / EP) and basalt fiber composites modified with a concentration ratio of zinc salt solution to 2-methylimidazole solution of 1:2 (named BF-PDA@ZIF-8-2 / EP) were immersed in the simulation for 4 weeks. Four basalt fiber composites were taken out every week to test the bending performance, as Figure 9 shown. The mechanical properties of basalt fiber composites before and after ZIF-8 modification show a downward trend in seawater. The bending strength retention rate of the modified basalt fiber composites is 4.25% higher on average at each time point than that of the unmodified basalt fiber composites, proving that the corrosion resistance of the modified basalt fiber composites has been greatly enhanced.

[0051] As mentioned above, this is not any form of limitation to the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the technical solution of the present invention, make some changes or modifications to the equivalent embodiments of equivalent changes by using the technical content disclosed above. However, as long as it does not depart from the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials, characterized in that: The following steps are involved: S1, after basalt fiber is placed in an organic solvent for high-temperature reflux, it is washed and dried to obtain desized basalt fiber, and then tris(hydroxymethylaminomethane) buffer is added to a dopamine hydrochloride solution, the desized basalt fiber is immersed in the solution for reaction, and then washed and dried to obtain a basalt fiber coated with polydopamine; in the step S1, the organic solvent is acetone and ethyl acetate, and the volume ratio is 3:1; the mass ratio of desized basalt fiber to dopamine solution is 1:50, the reaction temperature is 40°C, the stirring speed is 500rpm, the reaction time is 8 hours, and the polydopamine coverage rate reaches more than 80%; S2, immersing the polydopamine-coated basalt fiber obtained in S1 into a zinc salt solution for low-temperature reaction, washing, and drying to obtain a zinc salt-soaked basalt fiber; the zinc salt solution in S2 contains zinc nitrate hexahydrate as the solute, methanol as the solvent, a concentration of 0.15-0.3 mol / L, a stirring speed of 300 rpm, a stirring time of 1 hour, a stirring temperature of 40°C, an immersion reaction time of 6-9 hours, an immersion reaction temperature of 5°C-10°C, a whisker length of 100-300 nm, a diameter of 20-50 nm, and a whisker surface roughness Ra of 50-80 nm; S3, immersing the basalt fiber soaked in zinc salt obtained in S2 in a 2-methylimidazole solution, reacting at a constant temperature, washing and drying, and obtaining a basalt fiber modified with ZIF-8; in the step S3, the crystal particle size of the ZIF-8 is 50-200nm; the molar ratio of zinc ion (Zn²⁺) to 2-methylimidazole is 1:1.5-1:2.5; the thickness of the ZIF-8 modification layer is 2-5μm, the surface roughness of the ZIF-8 modified basalt fiber is 0.3-0.5μm, the pH value is 5.5-6.0, and the ZIF-8 coverage rate reaches 90%; S4, mixing the epoxy resin and the curing agent, adding a catalyst, and vacuum degassing for later use; S5. Electrostatically apply the mixture of the resin and the curing agent obtained in S4 to the surface of the ZIF-8 modified basalt fiber obtained in S3, then lay the electrostatically coated basalt fiber on a mold, and then obtain a basalt fiber composite material by a segmented hot pressing method.

2. A method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials according to claim 1, characterized in that: The solute of the 2-methylimidazole solution in step S3 is 2-methylimidazole, the solvent is methanol solution, the concentration is 0.2-0.4 mol / L, the stirring speed is 300 rpm, the stirring time is 1 hour, the soaking reaction time is 6-9 hours, and the reaction temperature is 50°C.

3. The method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials according to claim 1, characterized in that: The epoxy resin in step S4 is E51 epoxy resin, the catalyst is calcium oxide (CaO), the curing agent is methyltetrahydrophthalic anhydride, the mass ratio of epoxy resin to curing agent is 10:8, and the mass ratio of calcium oxide (CaO) to the total mass ratio of epoxy resin and curing agent is 0.1-0.5%.

4. The method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials according to claim 1, characterized in that: In step S4, the stirring speed is 300 rpm, the stirring temperature is 35°C, and the stirring time is 30 minutes; the vacuum degassing is divided into two steps, the first step is a vacuum degree of 10 MPa, the time is 10-15 minutes, and the second step is a vacuum degree of 5 MPa, and the time is 5-10 minutes.

5. The method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials according to claim 1, characterized in that: The coating viscosity of the electrostatic coating technology in step S5 should be controlled at 150-250mPa·s (measured at 25°C), the electrostatic voltage of the spray gun is 20-30kV, the coating thickness is controlled at 50-70μm, the distance between the spray gun and the basalt fiber surface should be 15-25cm, the spraying air pressure is set to 0.2-0.5MPa, the coating temperature should be 25-35°C, and the humidity of the electrostatic coating is 40-60%.

6. The method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials according to claim 1, characterized in that: In step S5, the basalt fibers are laid on the mold in layers in an alternating manner of 15° / 60° and 60° / 90° staggered angles between each layer.

7. The method for enhancing the interface bonding and corrosion resistance of basalt fiber composite materials according to claim 1, characterized in that: The segmented hot pressing method in step S5 is divided into three stages. The first stage is a pre-curing stage, with a pressure of 0.5 MPa, a temperature of 80°C, and a time of 30 minutes; the second stage is a temperature and pressure increase stage, with the first pressure increase to 2 MPa and the temperature increased to 120°C, and the second pressure increase to 5 MPa and the temperature increased to 150°C, and both pressure increases are maintained for 1 hour; the third stage is a temperature reduction and constant pressure stage, with a pressure of 5 MPa and a temperature of room temperature, and the interface porosity of the composite material is ≤0.5%, and the pore size is ≤5 μm.

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