Simple and efficient glass fiber fabric surface fluorination method

Abstract

The invention discloses a simple and efficient glass fiber fabric surface fluorination method, and belongs to the technical field of glass fiber fabric surface structure regulation and control. The fluorination method for the surface of the glass fiber fabric comprises the following steps: sequentially dipping glass fibers in a dopamine hydrochloride solution and a fluorine-containing silane coupling agent solution to obtain modified glass fibers. Firstly, polydopamine (PDA) is used for treating the surface of the fiber, then a fluorine-containing silane coupling agent is used for conducting structural design on the surface of the glass fiber, and comprehensive improvement of the interface bonding strength and the insulating property of the glass fiber epoxy resin composite material is achieved. The surface flashover voltage and the breakdown field strength of the composite material provided by the invention are remarkably improved, the treatment method is simple and convenient, and industrial batch preparation of the high-performance composite material can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface structure regulation of glass fiber fabrics, and more specifically relates to a simple and efficient fluorination method for the surface of glass fiber fabrics. Background Art

[0002] Glass fiber epoxy composites have excellent mechanical and electrical properties, and also have high sealing performance and good processability. They are widely used in the insulation and encapsulation of high- and low-voltage electrical appliances, motors, and electronic components, and have become one of the basic materials in the electrical and electronic industries. However, with the expansion of the application fields, glass fiber epoxy composites often face severe operating environments of high temperature and high humidity. Especially in the field of high-voltage insulation, the epoxy composite insulation materials also bear high-voltage electric fields and mechanical loads, which makes it extremely easy for defects to appear at the interface between glass fibers and epoxy resins, reducing the mechanical strength of the composites. In addition, when there is a high-voltage electric field, local discharge phenomena are likely to occur at the interface defects, thereby triggering electrical breakdown of the materials and causing the failure of glass fiber epoxy resin composites. Therefore, targeted structural design of the composite interface between glass fibers and epoxy resins has become an important means to enhance the insulation strength of composites in severe operating environments.

[0003] Currently, the interface performance is mainly improved through two ways: roughening the fiber surface and grafting active groups. Among them, roughening the fiber surface is mainly achieved through chemical etching and physical coating. The chemical etching method usually uses active reagents such as strong acids and strong bases to etch the surface, and the reaction is relatively violent, with high modification efficiency and obvious effects. However, it will damage the fiber body and reduce the overall performance. The physical coating method has a relatively mild reaction and can protect the fiber body, but the modification efficiency is low and the surface activity improvement is poor. The second way is to graft active groups, mainly through two methods: "bottom-up" growth and "top-down" grafting. "Bottom-up" growth is to grow nanoparticles such as TiO2 and ZnO on the fiber surface through methods such as air calcination and hydrothermal synthesis to increase the reaction sites with the resin matrix, thereby effectively improving the interfacial bonding strength. "Top-down" grafting usually grafts prepared molecules or groups with different polarities onto the fiber surface through techniques such as plasma, ultrasonic radiation, and electric field-assisted deposition. While roughening the fiber surface, a large number of active groups are introduced, thereby increasing the mechanical meshing and chemical bonding sites. Therefore, at present, the fiber surface modification usually uses a combination of multiple methods to enhance the fiber surface roughness and introduce a large number of active groups.

[0004] However, the above-mentioned treatment methods still have the following defects: Strong modification methods may damage the bulk structure of the fibers. Mild modification methods have low modification efficiency. The method of growing nanoparticles on the fiber surface also has the problem of poor adhesion between the nanoparticles and the fiber. That is, the existing modification methods all have some disadvantages and rarely can achieve the simultaneous improvement of mechanical properties and insulation properties. Moreover, the composites prepared by the above methods focus more on the research of mechanical properties and less on the research of insulation properties. Therefore, it is of great significance to develop a glass fiber epoxy resin composite with synergistically improved mechanical properties and insulation properties. Summary of the Invention

[0005] The object of the present invention is to provide a simple and efficient fluorination method for the surface of glass fiber fabrics to solve the problems existing in the above-mentioned prior art, achieve the synergistic improvement of the mechanical properties and insulation properties of glass fiber epoxy resin composites, and realize the preparation of epoxy composites with high creepage withstand voltage performance mainly for the field of electrical insulation materials.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: Provide a fluorination method for the surface of glass fiber, including the following steps:

[0008] Immerse the glass fiber in hydrochloric acid dopamine solution and fluorosilane coupling agent solution in sequence to obtain modified glass fiber.

[0009] Preferably, the concentration of the hydrochloric acid dopamine solution is 1.5 - 2 g / L, and the pH value is 8 - 9.

[0010] Preferably, the immersion time of the glass fiber in the hydrochloric acid dopamine solution is 10 - 16 h.

[0011] Preferably, the fluorosilane coupling agent in the fluorosilane coupling agent solution includes one or more of trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, (3,3,3-trifluoropropyl)trimethoxysilane, and 1H,1H,2H,2H-perfluorooctyltrimethoxysilane; the mass fraction of the fluorosilane coupling agent solution is 5 - 30%.

[0012] Further, the solvent in the fluorosilane coupling agent solution is ethanol and water, and the mass ratio of ethanol to water is 9:1.

[0013] Preferably, the immersion time of the glass fiber in the fluorosilane coupling agent solution is 4 - 8 h.

[0014] Further, after each immersion, there is also a drying step; the drying temperature is 60°C, and the time is 30 min.

[0015] Technical solution two of the present invention: Provide modified glass fibers prepared by the above fluorination method.

[0016] Technical solution three of the present invention: Provide a method for preparing a glass fiber epoxy resin composite material, comprising the following steps:

[0017] Mix epoxy resin, curing agent and accelerator to obtain an epoxy resin mixture;

[0018] Assemble the above modified glass fibers and the epoxy resin mixture to obtain a glass fiber epoxy resin composite material.

[0019] Preferably, the epoxy resin includes one or more of bisphenol A epoxy resin, epoxy resin E-44 and epoxy resin DER 732; the curing agent includes one or more of methyltetrahydrophthalic anhydride, curing agent T-31 and curing agent NX 2040; the accelerator includes 2,4,6-tris(dimethylaminomethyl)phenol.

[0020] Preferably, the assembly includes: Pouring the epoxy resin mixture into a mold lined with modified glass fibers and performing hot pressing.

[0021] Preferably, the temperature of the hot pressing is 120-140°C, the pressure is 8-12 MPa, and the time is 20-30 min.

[0022] Technical solution four of the present invention: Provide a glass fiber epoxy resin composite material prepared by the above preparation method.

[0023] Technical solution five of the present invention: Provide an application of the above modified glass fibers or the above glass fiber epoxy resin composite material in the field of electrical insulation materials.

[0024] The technical mechanism of the present invention is as follows:

[0025] The present invention uses polydopamine (PDA) as a physical coating material for glass fibers, which has excellent adhesion and can form a coating with a nanoscale thickness on the surface of glass fibers. While protecting the glass fiber body, it can also serve as a secondary reaction platform to provide the possibility for the grafting of fluorosilane coupling agents.

[0026] The structure of the fluorosilane coupling agent contains silane oxy groups with strong affinity for inorganic substances and organic functional groups with strong activity for organic substances. This unique structure enables it to form a transition layer between glass fiber and epoxy resin, thereby enhancing the interfacial bonding strength between the two and improving the overall performance of the composite material. In addition, by using the fluorosilane coupling agent to modify the glass fiber, fluorine-containing active groups can be introduced onto the fiber surface, activating the fiber surface activity, enhancing the interfacial bonding effect of the glass fiber epoxy resin composite material, and reducing internal defects. Moreover, the strongly electronegative fluorine element can effectively adsorb free electrons, increasing the energy level and density of the deep traps in the composite material, restricting the migration of free electrons, and thus improving the insulation strength of the composite material. The synergistic improvement of the interfacial bonding and insulation strength of the glass fiber epoxy resin composite material can be achieved.

[0027] By constructing the microstructure of the fluorosilane coupling agent at the interface of the glass fiber and epoxy resin composite material, the present invention can effectively enhance the bonding strength between the glass fiber and the epoxy resin matrix, thereby achieving the synergistic improvement of the mechanical properties and insulation properties of the glass fiber epoxy resin composite material.

[0028] The present invention selects the fluorosilane coupling agent. Compared with other types of silane coupling agents, fluorine has extremely strong electronegativity, which can effectively attract and bind free electrons, greatly hindering the transmission speed of free electrons. This has a good promoting effect on the insulation performance. In addition, fluorine-containing active groups can be introduced onto the fiber surface through the fluorine-containing coupling agent, activating the fiber surface activity, enhancing the interfacial bonding effect of the glass fiber epoxy resin composite material, reducing the existence of interfacial defects, improving the mechanical properties of the material, and further enhancing the insulation performance of the material.

[0029] Carbon fiber epoxy resin composite materials have become the core materials in the fields of aerospace, new energy vehicles, high-end equipment manufacturing, etc. due to their characteristics such as lightweight, high strength, and corrosion resistance. For carbon fiber / epoxy resin composite materials, the current mainstream research direction is the research on mechanical properties, and the modification method is mainly to improve its mechanical properties. However, due to the strong conductivity of carbon fibers, they are less used in the field of insulating materials. Glass fiber has excellent insulation performance and is the main reinforcing material for the insulating pull rod, the core component of the current gas-insulated metal-enclosed switchgear (GIS). Therefore, this application mainly focuses on the research of its insulation performance, and the modification method is mainly to improve its insulation performance. The discussion on mechanical properties pays more attention to the interfacial bonding situation of the composite material, and the enhancement of the interfacial bonding performance will also promote the improvement of the insulation performance.

[0030] The present invention discloses the following technical effects:

[0031] The present invention provides a method for designing the interfacial structure of a glass fiber epoxy composite material. By pretreating the surface of glass fiber with polydopamine and then grafting a silane coupling agent containing a fluorinated long chain on its surface, the interfacial structure between the glass fiber and the epoxy resin is changed, the bonding strength of the glass fiber epoxy resin interface is improved, the flashover voltage of the composite material is enhanced, and the surface insulation characteristics are improved. The preparation method of the glass fiber epoxy composite material provided by the present invention can effectively improve its surface flashover voltage and breakdown field strength, and the treatment means used can achieve industrial batch preparation. Brief Description of the Drawings

[0032] Figure 1 It is a flow chart of the fluorination method for the surface of the glass fiber fabric described in the present invention;

[0033] Figure 2 It is a surface SEM image of the modified glass fiber obtained in Examples 1-5 and Comparative Example 1, where (a) is Comparative Example 1, and (b)-(f) correspond to Examples 1-5 in sequence;

[0034] Figure 3 It is a schematic diagram of the DC flashover test platform for the glass fiber epoxy resin composite material;

[0035] Figure 4 It is a schematic diagram of the charge dissipation test platform for the glass epoxy resin fiber composite material;

[0036] Figure 5 It is a schematic diagram of the breakdown field strength test platform for the glass fiber epoxy resin composite material;

[0037] Figure 6 It is the flashover voltage test results of the glass fiber epoxy resin composite material obtained in Examples 1-5 and Comparative Example 1;

[0038] Figure 7 It is the charge dissipation test results of the glass fiber epoxy resin composite material obtained in Examples 1-5 and Comparative Example 1;

[0039] Figure 8 It is the breakdown field strength test results of the glass fiber epoxy resin composite material obtained in Examples 1-5 and Comparative Example 1;

[0040] Figure 9 It is a cross-sectional SEM image of the glass fiber epoxy resin composite material obtained in Example 3. Detailed Embodiments

[0041] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0042] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0044] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0045] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0046] It should be noted that those aspects not described in detail in the present invention are all conventional operating means in the art and are not the focus of the present invention.

[0047] Trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17) used in the following examples and comparative examples of the present invention, with a purity of 98%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0048] The glass fiber used in the following examples and comparative examples of the present invention was purchased from China National Bluestar (Group) Co., Ltd.

[0049] Other raw materials used in the following examples and comparative examples of the present invention are all commercially available products unless otherwise specified, and the sources of the commercially available products do not affect the technical effects of the present invention.

[0050] Unless otherwise specified, the room temperature involved in the present invention is calculated as 25 ± 5°C.

[0051] Example 1

[0052] This example provides a method for fluorination of the surface of a glass fiber fabric, and the specific steps are as follows:

[0053] (1) Immerse the glass fiber in an absolute ethanol solution and ultrasonically clean it for 2 h to wash away impurities such as sizing agents on the surface of the glass fiber. Then dry it in a vacuum oven at 60 °C for 12 h to obtain clean glass fiber.

[0054] (2) Prepare a 2 g / L dopamine hydrochloride solution and adjust the pH value of the solution to 8.5 with tris (hydroxymethyl) aminomethane (Tris). Subsequently, immerse the clean glass fiber in the dopamine hydrochloride solution and mechanically stir it at room temperature for 12 h. After the reaction, wash it 3 times with deionized water and then dry it in a vacuum oven at 60 °C for 30 min to obtain glass fiber pretreated with polydopamine.

[0055] (3) Prepare an ethanol aqueous solution of 5 wt% trimethoxy (1H,1H,2H,2H - heptadecafluorodecyl) silane (FAS - 17), mechanically stir it at room temperature for 15 min to fully hydrolyze it, ensuring that the mass ratio of ethanol to water is 9:1. Immerse the glass fiber pretreated with polydopamine in the 5 wt% FAS - 17 ethanol aqueous solution for 6 h, and then place it in a forced - air drying oven and dry it at 60 °C for 30 min. The modified glass fiber can be obtained.

[0056] (4) Prepare a glass fiber epoxy resin composite. According to the mass ratio of bisphenol A epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6 - tris (dimethylaminomethyl) phenol = 100:80:1, first mix the epoxy resin and methyltetrahydrophthalic anhydride, stir it in an oil bath at 60 °C for 10 min at a rotation speed of 600 r / min, then add 2,4,6 - tris (dimethylaminomethyl) phenol and continue to stir at the same rotation speed and temperature for 10 min. Then pour the mixture into a mold lined with modified glass fiber, place it on a vulcanizer at 140 °C, and hot - press it at 10 MPa for 25 min to obtain a glass fiber epoxy resin composite (where the mass fraction of glass fiber is 60% of the total mass of glass fiber and epoxy resin).

[0057] Example 2

[0058] The difference from Example 1 is that the mass fraction of the ethanol aqueous solution of trimethoxy (1H,1H,2H,2H - heptadecafluorodecyl) silane (FAS - 17) is adjusted to 10 wt%, and the others are the same as in Example 1.

[0059] Example 3

[0060] The difference from Example 1 is that the mass fraction of the ethanol aqueous solution of trimethoxy (1H,1H,2H,2H - heptadecafluorodecyl) silane (FAS - 17) is adjusted to 15 wt%, and the others are the same as in Example 1.

[0061] Example 4

[0062] The difference from Example 1 is that the mass fraction of the ethanol aqueous solution of trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17) is adjusted to 20 wt%, and the others are the same as in Example 1.

[0063] Example 5

[0064] The difference from Example 1 is that the mass fraction of the ethanol aqueous solution of trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17) is adjusted to 30 wt%, and the others are the same as in Example 1.

[0065] Comparative Example 1

[0066] The difference from Example 3 is that the step of impregnating in the ethanol aqueous solution of trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17) is omitted, and the others are the same as in Example 3.

[0067] Specifically:

[0068] (1) Immerse the glass fiber in an anhydrous ethanol solution and ultrasonically clean it for 2 h to wash away impurities such as sizing agents on the surface of the glass fiber. Then dry it in a vacuum oven at 60 °C for 12 h to obtain clean glass fiber.

[0069] (2) Prepare a 2 g / L dopamine hydrochloride solution and adjust the pH value of the solution to 8.5 with tris(hydroxymethyl)aminomethane (Tris). Subsequently, immerse the clean glass fiber in the dopamine hydrochloride solution and mechanically stir it at room temperature for 12 h. After the reaction, wash it 3 times with deionized water, and then dry it in a vacuum oven at 60 °C for 30 min to obtain modified glass fiber.

[0070] (3) Prepare a glass fiber epoxy resin composite. According to the mass ratio of bisphenol A epoxy resin:methyltetrahydrophthalic anhydride:2,4,6-tris(dimethylaminomethyl)phenol = 100:80:1, first mix the epoxy resin and methyltetrahydrophthalic anhydride, stir it in an oil bath at 60 °C for 10 min at a rotation speed of 600 r / min, and then add 2,4,6-tris(dimethylaminomethyl)phenol and continue to stir at the same rotation speed and temperature for 10 min. Then pour the mixture into a mold lined with modified glass fiber, place it on a vulcanizer at 140 °C, and hot press it at 10 MPa for 25 min to obtain a glass fiber epoxy resin composite (where the mass ratio of glass fiber is 60% of the total mass of glass fiber and epoxy resin).

[0071] Figure 2 are the surface SEM images of the modified glass fibers obtained in Examples 1 to 5 and Comparative Example 1. Among them, (a) is Comparative Example 1, and (b) to (f) correspond to Examples 1 to 5 in sequence. By Figure 2It can be seen that as the concentration of trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17) increases, the surface of the glass fiber is gradually covered, and the voids between the fiber bundles are also gradually filled. This makes the surface roughness of the fiber gradually increase. In addition, it can also demonstrate the successful deposition of the fluorosilane coupling agent.

[0072] The flashover voltages of the glass fiber epoxy resin composites obtained in Examples 1-5 and Comparative Example 1 were tested. The schematic diagram of the test platform is as Figure 3 shown, and the results are as Figure 6 shown.

[0073] Test method: In a high-voltage shielding box with constant temperature and humidity (temperature 25°C, humidity 45%), the flashover voltage of the glass fiber epoxy resin composite surface was tested using the uniform voltage increase method. Finger electrodes were used, and the electrode spacing was 5 mm. A negative-polarity DC power supply was used, and the voltage was uniformly increased at a rate of 50 V / s until surface flashover occurred. The signal at the moment of flashover was transmitted to the oscilloscope for display through a high-voltage measurement probe, and the flashover voltage value was read.

[0074] Figure 6 The flashover voltage test results of the glass fiber epoxy resin composites obtained in Examples 1-5 and Comparative Example 1. From Figure 6It can be seen that the flashover voltage of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent is 8.17 kV. After grafting fluorosilane coupling agent on the glass fiber surface, the flashover voltage increases to varying degrees. With the increase of the concentration of fluorosilane coupling agent, the flashover voltage of the glass fiber epoxy resin composite shows a trend of first increasing and then decreasing. This is because when the concentration of fluorine-containing coupling agent is low, with the increase of the concentration, the fluorine-containing groups on the fiber surface increase. At this time, the fluorine-containing groups play a dominant role, and the strongly electronegative fluorine element can effectively adsorb free electrons, thereby increasing the breakdown field strength of the composite material. However, when the concentration continues to increase, the trap energy and density in the material are relatively high at this time, and charges are likely to accumulate in large quantities in a short time, which has a negative effect on the improvement of the insulation performance, and the flashover voltage of the composite material begins to decline. When the concentration of fluorosilane coupling agent is 5 wt%, the flashover voltage is 10.12 kV, which is 23.87% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent. When the concentration of fluorosilane coupling agent is 10 wt%, the flashover voltage is 11.65 kV, which is 42.59% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent. When the concentration of fluorosilane coupling agent is 15 wt%, the flashover voltage is 13.89 kV, which is 70.01% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent. When the concentrations of fluorosilane coupling agent are 20 wt% and 30 wt% respectively, the flashover voltages are 12.88 kV and 11.99 kV respectively. In addition, it is also shown that the optimal concentration of fluorosilane coupling agent is 15 wt%.

[0075] The charge dissipation of the glass fiber epoxy resin composites obtained in Examples 1 to 5 and Comparative Example 1 was tested. The schematic diagram of the test platform is as Figure 4 shown, and the results are as Figure 7 shown.

[0076] Test method: First, place the glass fiber epoxy resin composite material (sample) horizontally on the aluminum foil, and use a negative-polarity high-voltage DC power supply to charge the sample, ensuring that the corona tip part is 5 mm directly above the sample, and the charging duration is 120 s. Then, turn off the high-voltage power supply, move the sample under the probe (Trek P0864) of the series-connected electrometer (Trek 3455ET), and the distance between the two is 2 mm. Use a data acquisition card to monitor the surface potential for 750 s.

[0077] Figure 7 For the charge dissipation test results of the glass fiber epoxy resin composites obtained in Examples 1 to 5 and Comparative Example 1. From Figure 7It can be seen that for the glass fiber epoxy resin composite material without treatment with fluorosilane coupling agent, about 35% of the charge dissipated within the test time. When the concentration of the introduced fluorosilane coupling agent increased, the charge dissipation rate of the glass fiber epoxy resin composite material began to slow down. This is because the fluorine-containing group has a very strong electronegativity, which can effectively bind free electrons and restrict the migration of free electrons. Therefore, after introducing fluorine-containing groups on the fiber surface, the energy level and density of the deep traps in the composite material are increased, and the number of captured free electrons increases, so the surface charge dissipation rate becomes slower. When the concentration of the fluorosilane coupling agent is 5wt%, about 8.5% of the charge dissipates. When the concentration of the fluorosilane coupling agent is 10wt%, about 4.5% of the charge dissipates. When the concentration of the fluorosilane coupling agent is 15wt%, about 4.0% of the charge dissipates. When the concentration of the fluorosilane coupling agent is 20wt%, about 2.5% of the charge dissipates. When the concentration of the fluorosilane coupling agent is 30wt%, about 1.2% of the charge dissipates. It shows that after fluorination, rapid migration of surface charges on the glass fiber epoxy resin composite material can be avoided, thereby enhancing the surface flashover voltage of the composite material.

[0078] The breakdown field strengths of the glass fiber epoxy resin composite materials obtained in Examples 1 to 5 and Comparative Example 1 were tested. The schematic diagram of the test platform is as Figure 5 shown, and the results are as Figure 8 shown.

[0079] Test method: The breakdown field strength test uses a sphere-sphere electrode, and the glass fiber epoxy resin composite material (sample) is placed between the electrodes. The pressurization experiment is carried out in dimethyl silicone oil. The high-voltage AC unit mainly consists of a voltage regulator and a step-up transformer. The input voltage of the voltage regulator is 220 kV AC power frequency. When the sample is broken down and conducted, the over-current relay inside the device will automatically cut off the power supply to protect the experimental circuit, and record the voltage level at breakdown.

[0080] Figure 8 are the test results of the breakdown field strengths of the glass fiber epoxy resin composite materials obtained in Examples 1 to 5 and Comparative Example 1. From Figure 8It can be seen that the breakdown voltage of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent is 34.7 kV. After grafting fluorosilane coupling agent on the surface of glass fiber, the breakdown voltage increases to varying degrees. With the increase of the concentration of fluorosilane coupling agent, the breakdown field strength of the glass fiber epoxy resin composite shows a trend of first increasing and then decreasing. This is because when the concentration of fluorine-containing coupling agent is relatively low, with the increase of the concentration, the fluorine-containing groups on the fiber surface increase. At this time, the fluorine-containing groups play a dominant role, and the strongly electronegative fluorine element can effectively adsorb free electrons, thereby increasing the breakdown field strength of the composite material. However, when the concentration continues to increase, the trap energy and density in the material are relatively high at this time, and charges are likely to accumulate in large quantities in a short time, which has a negative effect on the improvement of insulation performance. The flashover voltage of the composite material begins to decline, and the breakdown electric field also shows a decreasing trend. When the concentration of fluorosilane coupling agent is 5 wt%, the breakdown voltage is 49.8 kV, which is 43.52% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent. When the concentration of fluorosilane coupling agent is 10 wt%, the breakdown voltage is 51.65 kV, which is 48.85% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent. When the concentration of fluorosilane coupling agent is 15 wt%, the breakdown voltage is 54.96 kV, which is 58.37% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent. When the concentrations of fluorosilane coupling agent are 20 wt% and 30 wt% respectively, the breakdown voltages are 52.1 kV and 50.9 kV respectively, which are 50.14% and 46.69% higher than that of the glass fiber epoxy resin composite without treatment with fluorosilane coupling agent.

[0081] Comparative Example 2

[0082] The difference from Example 3 is that "trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17)" is replaced with an equal amount of "γ-aminopropyltriethoxysilane coupling agent", and the others are the same as in Example 3.

[0083] Comparative Example 3

[0084] The difference from Example 3 is that the impregnation step in the hydrochloric acid dopamine solution is omitted, and the others are the same as in Example 3.

[0085] Specifically:

[0086] (1) Immerse the glass fiber in an anhydrous ethanol solution and ultrasonically clean it for 2 h to wash away impurities such as sizing agents on the surface of the glass fiber. Then dry it in a vacuum oven at 60 °C for 12 h to obtain clean glass fiber.

[0087] (2) Prepare an ethanol aqueous solution containing 15 wt% of trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (FAS-17), and mechanically stir it at room temperature for 15 min to fully hydrolyze it. Ensure that the mass ratio of ethanol to water is 9:1. Immerse the clean glass fiber in the 15 wt% FAS-17 ethanol aqueous solution for 6 h, and then place it in a blast drying oven and dry it at 60 °C for 30 min. The modified glass fiber can be obtained.

[0088] (3) Prepare a glass fiber epoxy resin composite. According to the mass ratio of bisphenol A epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethylaminomethyl)phenol = 100:80:1, first mix the epoxy resin and methyltetrahydrophthalic anhydride, and stir in an oil bath at 60 °C for 10 min with a rotation speed of 600 r / min. Then add 2,4,6-tris(dimethylaminomethyl)phenol and continue to stir at the same rotation speed and temperature for 10 min. Pour the mixed solution into a mold lined with modified glass fiber, place it on a vulcanizer at 140 °C, and hot press it at 10 MPa for 25 min to obtain a glass fiber epoxy resin composite (where the mass ratio of glass fiber is 60% of the total mass of glass fiber and epoxy resin).

[0089] The flashover voltage, breakdown field strength, and shear strength of the materials obtained in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in Table 1. Among them, the shear strength is detected according to the standard of GB / T 1450.1-2005.

[0090] Table 1 Test effect data of Example 3 and Comparative Examples 1-3

[0091]

[0092] Table 2

[0093]

[0094] In Table 2, the treatment method of g-C3N4 modification refers to the reference: Xu, Huan; Zhu, Song-Qing; Yang, Chun; Dang, Rui-Qiong; Lin, Ben-Cai; Yang, Wan-Yi; Guan, Ji-Peng; Shen, Xiao-Jun. Effect of O-C3N4 on the mechanical properties of glass fiber / epoxy resin composites. Polymer Composites. The treatment methods for filling graphene nanosheets, nanoaluminum, and copper refer to the reference: Megahed, M., Sakr, A.S., Badawy, A.A.M. et al. Assessment of the performance of aluminum, copper, and graphene nanometer fillers filled woven glass fiber / epoxy composites. J Polym Res 31, 29 (2024). The treatment method for filling carbon nanotubes refers to the reference: V.C.S. Chandrasekaran, S.G. Advani, M.H. Santare, Influence of resin properties on interlaminar shear strength of glass / epoxy / MWNT hybrid composites, Composites Part A: Applied Science and Manufacturing, Volume 42, Issue 8, 2011, https: / / doi.org / 10.1016 / j.compositesa.2011.04.004. The treatment method for filling graphene nanosheets refers to the reference: Wang, F., Drzal, L.T., Qin, Y. et al. Size effect of graphene nanoplatelets on the morphology and mechanical behavior of glass fiber / epoxy composites. J Mater Sci 51, 3337-3348 (2016).

[0095] As can be seen from Tables 1 and 2, the present invention can synergistically improve the mechanical properties and insulation properties of the obtained composite materials.

[0096] Figure 9SEM cross-sectional view of the glass fiber epoxy resin composite obtained in Example 3. As can be seen from Figure 9 it, in the present invention, polydopamine (PDA) is used as a physical coating material for glass fibers, which has excellent adhesion and can form a coating with a nanoscale thickness on the surface of glass fibers. While protecting the glass fiber body, it can also serve as a secondary reaction platform, providing the possibility for the grafting construction of fluorosilane coupling agents.

[0097] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0098] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for fluorination of the surface of glass fiber, characterized in that, It includes the following steps: The glass fiber is successively impregnated in a hydrochloric acid dopamine solution and a fluorosilane coupling agent solution to obtain a modified glass fiber.

2. The fluorination method according to claim 1, wherein The concentration of the hydrochloric acid dopamine solution is 1.5 - 2 g / L, and the pH value is 8 - 9; and / or, the impregnation time of the glass fiber in the hydrochloric acid dopamine solution is 10 - 16 h.

3. The fluorination method according to claim 1, characterized in that, The fluorosilane coupling agent in the fluorosilane coupling agent solution includes one or more of trimethoxy(1H,1H,2H,2H - heptadecafluorodecyl)silane, (3,3,3 - trifluoropropyl)trimethoxysilane, and 1H,1H,2H,2H - perfluorooctyltrimethoxysilane; the mass fraction of the fluorosilane coupling agent solution is 5 - 30%; and / or, the impregnation time of the glass fiber in the fluorosilane coupling agent solution is 4 - 8 h.

4. A modified glass fiber prepared by the fluorination method according to any one of claims 1 - 3.

5. A preparation method of a glass fiber epoxy resin composite material, characterized in that, It includes the following steps: Epoxy resin, a curing agent, and an accelerator are mixed to obtain an epoxy resin mixture. The modified glass fiber according to claim 4 and the epoxy resin mixture are assembled to obtain a glass fiber - epoxy resin composite material.

6. The preparation method according to claim 5, characterized in that, The epoxy resin includes one or more of bisphenol A - type epoxy resin, epoxy resin E - 44, and epoxy resin DER 732; the curing agent includes one or more of methyltetrahydrophthalic anhydride, curing agent T - 31, and curing agent NX 2040; the accelerator includes 2,4,6 - tris(dimethylaminomethyl)phenol.

7. The preparation method according to claim 5, characterized in that, The assembly includes: pouring the epoxy resin mixture into a mold paved with the modified glass fiber and performing hot pressing.

8. The preparation method according to claim 7, characterized in that, The temperature of the hot pressing is 120 - 140 °C, the pressure is 8 - 12 MPa, and the time is 20 - 30 min.

9. A glass fiber - epoxy resin composite material prepared by the preparation method according to any one of claims 5 - 8.

10. An application of the modified glass fiber according to claim 4 or the glass fiber - epoxy resin composite material according to claim 9 in the field of electrical insulation materials.

Images