Method for improving insulating property of glass fiber epoxy composite material by constructing nano ZnO one-dimensional structure

Abstract

The invention discloses a method for improving the insulating property of a glass fiber epoxy composite material by constructing a nano ZnO one-dimensional structure, and belongs to the technical field of electrical insulating materials. A film-shaped structure is formed on the surface of glass fiber by utilizing a polymerization reaction of dopamine, a secondary reaction platform is provided for subsequent treatment, and the insulating property of the glass fiber epoxy composite material is improved. A simple, environment-friendly, rich-variety and high-designability nanometer material modification method is adopted, nanometer ZnO is constructed on the surface of the glass fiber, the roughness degree of the surface of the glass fiber is increased, more binding sites with an epoxy resin matrix are provided, interface binding of the glass fiber and the epoxy resin is achieved, interface defects are made up, and the bonding strength of the glass fiber and the epoxy resin is improved. The risk of partial discharge at the interface of the glass fiber epoxy resin composite material under high voltage is reduced, and the mechanical property and the insulating property of the glass fiber epoxy resin composite material can be effectively enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical insulating materials, and particularly relates to a method for constructing a one-dimensional nanostructure of ZnO to improve the insulation performance of glass fiber epoxy composites. Background Art

[0002] High-voltage power transmission technology is an important boost for building a new power system with new energy as the main body and realizing a profound transformation in the energy and power industry. It is an important carrier for the wide-area supply and consumption of new energy and a key guarantee for the safe and stable supply of electric energy. Among them, power equipment represented by high-voltage switchgear, large transformers, and overhead transmission lines is a key hub in the high-voltage power transmission network. Improving the insulation strength and intelligence of equipment, reducing the size of equipment, and extending the operation and maintenance cycle are important measures to promote various power grid equipment into the future energy interconnection.

[0003] In recent years, with the rapid development of China's energy and power industry, a large number of large-scale high-voltage electrical equipment represented by gas-insulated switches (GIS) and gas-insulated transmission lines (GIL) have been put into operation in the power grid, playing a crucial role in the development of high-capacity DC power transmission. However, the epoxy composites used in the equipment often face a complex operating environment. At the gas-solid interface of the insulating material and the interface of the fiber-reinforced epoxy composite material, charges are easily accumulated under the action of an applied electric field, resulting in serious distortion of the electric field in a local area of the material surface, and then inducing surface flashover or partial discharge. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a method for constructing a one-dimensional nanostructure of ZnO (zinc oxide) to improve the insulation performance of glass fiber epoxy composites.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for constructing a one-dimensional nanostructure of ZnO to improve the insulation performance of glass fiber epoxy composites. First, a film-like structure is formed on the surface of glass fibers by the polymerization reaction of dopamine to obtain glass fibers pretreated with polydopamine. Then, ZnO nanostructures are constructed on the surface of the polydopamine-pretreated glass fibers to obtain glass fibers with a one-dimensional nanostructure of ZnO constructed on the surface. Finally, the glass fibers with a one-dimensional nanostructure of ZnO constructed on the surface are combined with epoxy resin.

[0007] Glass fiber reinforced polymer material (GFRP) is a new type of composite material with resin (RP) as the matrix and glass fiber (GF) as the reinforcement. Compared with traditional metal materials, GFRP has the characteristics of low density, not easily corroded, excellent electrical insulation, and high specific strength. Among GFRP, the composite material with epoxy resin as the matrix has the widest application. Glass fiber / epoxy resin composite material has the advantages of excellent insulation performance, high mechanical strength, and moderate price. Zinc oxide (ZnO), as a new type of nanoscale material, has superior properties. When ZnO is applied to fiber-reinforced composite materials, while retaining the excellent mechanical properties, insulation properties, and thermal stability of the fiber itself, ZnO also has a unique nanoscale structure, a relatively large band gap, and the one-dimensional nanostructure constructed on the fiber surface increases the specific surface area of the fiber surface, which can effectively enhance the interfacial bonding strength between glass fiber and polymers such as epoxy resin. Based on this, in the present invention, by performing surface activation treatment on glass fiber (i.e., forming a polydopamine film-like structure), the bonding strength between ZnO and epoxy resin matrix can be effectively enhanced, the dissipation rate of surface charge can be effectively regulated, the distortion of surface field strength can be alleviated, the surface flashover voltage can be increased, and the mechanical properties and insulation characteristics at the interface can be strengthened, thereby realizing the improvement of the insulation performance of glass fiber epoxy resin composite materials.

[0008] Furthermore, before forming a film-like structure on the surface of glass fiber by using the polymerization reaction of dopamine, it also includes a pretreatment process of cleaning and drying the glass fiber.

[0009] The present invention does not limit the pretreatment process of cleaning and drying the glass fiber, as long as the glass fiber can reach a clean state (free of impurities). Exemplarily, the pretreatment steps of cleaning and drying the glass fiber are as follows: Immerse the glass fiber in absolute ethanol, ultrasonically clean for 2 h to wash away the organic impurities on the fiber surface, and then dry in a vacuum oven at 80 °C for 12 h to obtain clean glass fiber.

[0010] Furthermore, the preparation steps of the glass fiber pretreated with polydopamine are: Immerse the glass fiber in an alkaline hydrochloric acid dopamine solution, stir, wash with water, and dry to obtain the glass fiber pretreated with polydopamine.

[0011] Furthermore, the preparation steps of the alkaline hydrochloric acid dopamine solution are: Use tris(hydroxymethyl)aminomethane (Tris) to adjust the pH of the hydrochloric acid dopamine solution to alkaline to obtain the alkaline hydrochloric acid dopamine solution.

[0012] Even further, the pH of the alkaline hydrochloric acid dopamine solution is 8.0 - 8.5.

[0013] Exemplarily, the preparation step of the alkaline dopamine hydrochloride solution is: adjusting the pH of a dopamine hydrochloride solution with a concentration of 2 g / L to 8.5 with Tris to obtain the alkaline dopamine hydrochloride solution.

[0014] Furthermore, the preparation steps of the polydopamine pretreated glass fiber are: adjusting the pH of a 2 g / L dopamine hydrochloride solution to 8.5 with Tris, then immersing 25 g of clean glass fiber in 1000 mL of the pH-adjusted dopamine hydrochloride solution, mechanically stirring at room temperature for 12 hours, washing with deionized water three times after the reaction is completed, and then drying in a vacuum oven at 40° C. for 24 hours to obtain polydopamine pretreated glass fiber.

[0015] Furthermore, the step of constructing nano ZnO on the surface of the polydopamine pretreated glass fiber is: immersing the polydopamine pretreated glass fiber in a ZnO seed solution, drying and annealing, and then immersing it in a ZnO growth solution for growth to obtain a glass fiber with a one-dimensional nano ZnO structure on the surface.

[0016] Furthermore, the preparation step of the ZnO seed solution is: mixing zinc acetate dihydrate (ZAD) and isopropanol, stirring evenly, adding triethylamine, and stirring evenly again to obtain the ZnO seed solution.

[0017] Furthermore, the preparation steps of the ZnO seed solution are: adding 5.5 g ZAD to 196.25 g isopropanol and stirring evenly, adding 2.55 g triethylamine and stirring well to obtain the ZnO seed solution.

[0018] Furthermore, the preparation step of the ZnO growth solution is: uniformly mixing a zinc nitrate standard solution and a hexamethylenetetramine (HMTA) solution to obtain a ZnO growth solution.

[0019] Further, the concentration of the ZnO growth solution is 0.05-0.15 mol / L. Exemplarily, the concentration of the ZnO growth solution is 0.05 mol / L, 0.1 mol / L or 0.15 mol / L.

[0020] Furthermore, the preparation step of the ZnO growth solution is: mixing and stirring the zinc nitrate standard solution and the HMTA solution of equal concentration and volume to obtain the ZnO growth solution.

[0021] Specifically, the steps for fabricating glass fibers with one-dimensional nanostructured ZnO on the surface are as follows: The poly-dopamine pretreated glass fibers are alternately immersed in a ZnO seed solution and a ZnO growth solution. First, immerse them in the ZnO seed solution for 10 min, dry at 80 °C for 30 min, and anneal at 150 °C for 10 min. Then, immerse them in the ZnO growth solution and grow at 93 °C for 4 h. In this way, one-dimensional nanostructured ZnO can be successfully fabricated on the glass fibers. In this step, by changing the concentration of the ZnO growth solution, glass fiber epoxy composites with one-dimensional nanostructured ZnO of different growth concentrations can be finally obtained.

[0022] Furthermore, the steps for fabricating the composite of the glass fibers with one-dimensional nanostructured ZnO and epoxy resin are as follows: Mix epoxy resin, a curing agent, and an accelerator, degas them under vacuum, and then impregnate the glass fibers. The glass fibers with one-dimensional nanostructured ZnO are located in the outermost layer. After impregnation, hot press and cure them. When preparing the glass fiber and epoxy resin composite with good insulation performance of the present invention, impregnate the glass fibers with the mixture of epoxy resin, a curing agent, and an accelerator degassed under vacuum. The glass fibers with one-dimensional nanostructured ZnO are located in the outermost layer. For example, when there are 4 layers of glass fibers, the middle two layers are glass fibers that have only been cleaned, and the outermost two layers are glass fibers with one-dimensional nanostructured ZnO.

[0023] Furthermore, the mass ratio of the epoxy resin, the curing agent, and the accelerator is 100∶80∶1.

[0024] Optionally, the epoxy resin is bisphenol A type epoxy resin, the curing agent is methyltetrahydrophthalic anhydride (MTHPA), and the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30).

[0025] Even further, the steps for fabricating the composite of the glass fibers with one-dimensional nanostructured ZnO and epoxy resin are as follows: Mix 60 g of bisphenol A type epoxy resin, the curing agent (MTHPA), and the accelerator (DMP-30) according to the mass ratio of 100∶80∶1 and stir evenly (the total mass of bisphenol A type epoxy resin, curing agent MTHPA, and accelerator DMP-30 is 60 g). After degassing under vacuum, impregnate the glass fibers with it, and place the glass fibers with one-dimensional nanostructured ZnO on the surface in the outermost layer. After impregnation, hot press at 140 °C / 10 MPa and cure continuously at 120 °C for 10 h.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] The present invention utilizes the polymerization reaction of dopamine to form a film-like structure on the surface of glass fibers, providing a secondary reaction platform for subsequent treatment. Then, a simple, environmentally friendly, rich in variety, and highly designable layer-by-layer self-assembly modification method is adopted to grow the one-dimensional nanostructure of ZnO on the surface of glass fibers, increasing the roughness of the glass fiber surface, providing more binding sites with the epoxy resin matrix, facilitating the interfacial bonding between glass fibers and epoxy resin, compensating for interfacial defects, reducing the risk of partial discharge at the interface of glass fiber epoxy resin composites under high voltage, and effectively enhancing the mechanical properties and insulation properties of glass fiber epoxy resin composites. The present invention focuses on the regulation of the interfacial structure between glass fibers and epoxy resin, with the advantages of simple operation and remarkable effects, and can provide high-performance insulating component raw materials for gas-insulated switchgear. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1 is a flowchart for constructing the one-dimensional nanostructure of ZnO on glass fibers;

[0030] Figure 2 are the microscopic characterization results before and after constructing the one-dimensional nanostructure of ZnO on glass fibers. Among them, (1) is the unmodified glass fiber, (2) is the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface at a growth concentration of 0.05 mol / L (i.e., the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface in Example 1), (3) is the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface at a growth concentration of 0.1 mol / L (i.e., the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface in Example 2), and (4) is the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface at a growth concentration of 0.15 mol / L (i.e., the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface in Example 3);

[0031] Figure 3 is a schematic diagram of the DC flashover test platform for the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface;

[0032] Figure 4 is a schematic diagram of the charge dissipation test platform for the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface;

[0033] Figure 5 is a schematic diagram of the breakdown field strength test platform for the glass fiber epoxy composite with the one-dimensional nanostructure of ZnO constructed on the surface;

[0034] Figure 6 Flashover voltage test results of glass fiber epoxy composites with one-dimensional nano-ZnO structures constructed on the surface;

[0035] Figure 7 Charge dissipation test results of glass fiber epoxy composites with one-dimensional nano-ZnO structures constructed on the surface;

[0036] Figure 8 Breakdown field strength test results of glass fiber epoxy composites with one-dimensional nano-ZnO structures constructed on the surface;

[0037] Figures 6 - 8 In the text, "unmodified" represents the glass fiber epoxy resin composite prepared in Comparative Example 1, "#1" represents the glass fiber epoxy composite with one-dimensional nano-ZnO structures constructed on the surface in Example 1, "#2" represents the glass fiber epoxy composite with one-dimensional nano-ZnO structures constructed on the surface in Example 2, and "#3" represents the glass fiber epoxy composite with one-dimensional nano-ZnO structures constructed on the surface in Example 3. Detailed implementation manners

[0038] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0039] It should be understood that the terms used in the present invention are only for describing specific implementation manners 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. Each 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 can be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those 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 can 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.

[0041] Without departing from the scope or spirit of the present invention, various modifications and variations to the specific embodiments of the description of the present invention will be apparent to those skilled in the art. Other embodiments obtained from the description of the present invention will be apparent to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0042] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0043] Figure 1 This is a flow chart for constructing a one-dimensional ZnO nanostructure on glass fibers of the present invention. Specifically: a polydopamine film is prepared on the surface of glass fibers (GF) through a polymerization reaction to obtain polydopamine-pretreated glass fibers (GF-P); the polydopamine-pretreated glass fibers are immersed in a ZnO seed solution, and after drying and annealing treatment, glass fibers with ZnO seeds grown on them (seed GF-P) are obtained. Then, the glass fibers with ZnO seeds grown on them are immersed in ZnO growth solutions with different concentrations, and finally, glass fibers with one-dimensional ZnO nanostructures constructed on their surfaces with different growth concentrations (GF-P-ZnO) can be obtained.

[0044] Specifically, the method for constructing a one-dimensional nanostructure of nano-ZnO to improve the insulation performance of glass fiber epoxy composites is as follows: The glass fiber pretreated with polydopamine is first immersed in a ZnO seed solution (the immersion time is 10 min), taken out and dried at 80 °C for 30 min, annealed at 150 °C for 10 min, and then immersed in a ZnO growth solution with a concentration of 0.05 mol / L and grown at 93 °C for 4 h to obtain glass fibers with a growth concentration of 0.05 mol / L and a one-dimensional nanostructure of nano-ZnO constructed on the surface. The above glass fibers with a one-dimensional nanostructure of nano-ZnO constructed on the surface are combined with epoxy resin to obtain glass fiber epoxy composites with improved insulation performance (denoted as #1); The glass fiber pretreated with polydopamine is first immersed in a ZnO seed solution (the immersion time is 10 min), taken out and dried at 80 °C for 30 min, annealed at 150 °C for 10 min, and then immersed in a ZnO growth solution with a concentration of 0.1 mol / L and grown at 93 °C for 4 h to obtain glass fibers with a growth concentration of 0.1 mol / L and a one-dimensional nanostructure of nano-ZnO constructed on the surface. The above glass fibers with a one-dimensional nanostructure of nano-ZnO constructed on the surface are combined with epoxy resin to obtain glass fiber epoxy composites with improved insulation performance (denoted as #2). The glass fiber pretreated with polydopamine is first immersed in a ZnO seed solution (the immersion time is 10 min), taken out and dried at 80 °C for 30 min, annealed at 150 °C for 10 min, and then immersed in a ZnO growth solution with a concentration of 0.15 mol / L and grown at 93 °C for 4 h to obtain glass fibers with a growth concentration of 0.15 mol / L and a one-dimensional nanostructure of nano-ZnO constructed on the surface. The above glass fibers with a one-dimensional nanostructure of nano-ZnO constructed on the surface are combined with epoxy resin to obtain glass fiber epoxy composites with improved insulation performance (denoted as #3).

[0045] The present invention utilizes the growth characteristics of ZnO to construct ZnO with a one-dimensional nanostructure on the surface of glass fibers, thereby improving the insulation performance of glass fiber epoxy composites. Different from the zinc oxide powder directly used in the prior art, one of the key points of the present invention is the ZnO growth process. The present invention uses a salt solution containing Zn atoms as the growth solution and prepares a one-dimensional nanostructure of nano-ZnO by hydrothermal synthesis method. As can be seen from the present invention Figure 2 the ZnO of the present invention has a linear-like structure, and the one-dimensional nanostructure of nano-ZnO is directly constructed on the surface of glass fibers, greatly improving the insulation performance of glass fiber epoxy composites.

[0046] Unless otherwise specified, the room temperature in the present invention is calculated as 25 ± 2 °C.

[0047] All raw materials used in the examples and comparative examples of the present invention were obtained through commercial purchases. As an example, the glass fiber was purchased from Langfang Anlang Sealing Materials Co., Ltd.; zinc acetate dihydrate (ZAD) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., isopropyl alcohol (C 3 H 8 O) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., triethylamine (C 6 H 15 N) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., zinc nitrate (Zn(NO 3 ) 2 ) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., hexamethylenetetramine (HMTA) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., absolute ethanol (analytical grade) was purchased from Aladdin Reagent (Shanghai) Co., Ltd.; dopamine (analytical grade) was purchased from Aladdin Reagent (Shanghai) Co., Ltd.; tris(hydroxymethyl)aminomethane (Tris) (analytical grade) was purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0048] In the following examples and comparative examples of the present invention, the curing agent was methyltetrahydrophthalic anhydride (MTHPA), and the accelerator was 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30).

[0049] In the following examples and comparative examples of the present invention, the purchased glass fiber was cut into 20×10 cm, which was called "1 piece of fiber cloth"; when preparing the glass fiber epoxy resin composite, 4 pieces of glass fiber cloth were selected. Among them, the unmodified glass fiber epoxy resin composite was obtained by directly stacking 4 pieces of glass fiber cloth and infiltrating them with a degassed mixture of bisphenol A epoxy resin, curing agent MTHPA and accelerator DMP-30 (mass ratio of 100∶80∶1); the glass fiber epoxy resin composite with nano-ZnO one-dimensional structure was obtained by replacing the top and bottom layers of the 4 pieces of glass fiber cloth with glass fibers with nano-ZnO one-dimensional structure on the surface and infiltrating them with a degassed mixture of bisphenol A epoxy resin, curing agent MTHPA and accelerator DMP-30 (mass ratio of 100∶80∶1).

[0050] In the following examples and comparative examples of the present invention, the mass ratio of glass fiber is 60%, and it is also ensured to be 60% after modification treatment. Specifically, when preparing the glass fiber epoxy resin composite material, 4 pieces of glass fiber cloth are selected. Comparing the composite material after modification treatment with the composite material without modification treatment, the main difference is that the top layer and the bottom layer of the 4 pieces of glass fiber cloth are replaced with the modified glass fiber cloth (i.e., the glass fiber with a one-dimensional nano-ZnO structure constructed on the surface). Therefore, the total mass of bisphenol A epoxy resin, curing agent MTHPA and accelerator DMP-30 is 60 g, and the weight of each piece of glass fiber cloth is 25 g, with 4 pieces of glass fiber cloth used. Then the mass ratio of the glass fiber cloth is 4×25 / (4×25 + 60) = 62.5%, that is, the mass ratio is approximately 60%.

[0051] "Mechanical stirring" refers to the stirring of a liquid by relying on the rotation of a stirrer in a stirring tank, which is a common method in chemical production to disperse gas, liquid or solid particles in a liquid.

[0052] It should be noted that the points not detailed in the present invention are all conventional operation means in the art and are not the focus of the present invention. For example, the preparation method of dopamine hydrochloride solution, hot pressing molding and other specific methods are all completed by conventional methods.

[0053] The focus of the present invention is to construct a one-dimensional nano-ZnO structure on the surface of the glass fiber, thereby enhancing the bonding strength between the glass fiber and the epoxy resin, and then improving the insulation performance of the glass fiber epoxy resin composite material. Compared with ZnO particles, the one-dimensional nano-structure can be arranged along a specific direction, forming a continuous insulation barrier on the surface of the glass fiber, blocking charges along the surface and dissipating them along the body, reducing the short-time local large accumulation of charges, preventing the distortion of the local electric field strength, and thus improving the insulation performance. In addition, when the particulate structure is compounded, agglomeration is likely to occur, it is difficult to disperse evenly, and the size distribution is uneven, while the size and morphology of the one-dimensional nano-structure have high controllability, which can effectively solve the problem of particle agglomeration and maximize the performance of ZnO. Different from the common method in the prior art of grafting functional groups (which can be understood as functionalized molecular segments) on the surface of glass fibers to improve insulation and mechanical properties. The present invention uses nano-ZnO to modify the glass fiber, combines the metal nano-material with the glass fiber, so that the superior performance of the metal nano-material is combined with the glass fiber. When forming a composite material with epoxy resin, the one-dimensional nano-structure on the fiber surface can be inserted into the interior of the epoxy resin, and the effective area in contact with the epoxy is larger than that of the particulate nano-structure, enhancing the mechanical meshing effect and the mechanical interlocking ability, thus reducing interface defects, and then improving the insulation performance of the composite material formed by the glass fiber and the epoxy resin, and this modification method will not damage the fiber itself.

[0054] The technical solution of the present invention will be further described below through embodiments.

[0055] Example 1

[0056] S1. Immerse the glass fiber in absolute ethanol and ultrasonically clean it for 2 h to wash away the organic impurities on the fiber surface. Then dry it in a vacuum oven at 80 °C for 12 h to obtain clean glass fiber.

[0057] S2. Adjust the pH of the hydrochloric acid dopamine solution with a concentration of 2 g / L to 8.5 using Tris. Then immerse 25 g of clean glass fiber into 1000 mL of the hydrochloric acid dopamine solution with adjusted pH 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 40 °C for 24 h to obtain glass fiber pretreated with polydopamine.

[0058] S3. Add 5.5 g of ZAD and 196.25 g of isopropanol into an oil bath pot, magnetically stir at 80 °C for 15 min, then dropwise add 2.55 g of triethylamine, continue to stir for 10 min, the solution gradually changes from turbid to clear, and then cool it to room temperature and let it stand for 3 h to obtain a ZnO seed solution.

[0059] S4. Mix equal volumes of a zinc nitrate standard solution with a concentration of 0.05 mol / L and an HMTA standard solution with a concentration of 0.05 mol / L, and stir well for 15 min to obtain a ZnO growth solution with a concentration of 0.05 mol / L.

[0060] S5. First immerse the glass fiber pretreated with polydopamine into the ZnO seed solution (the immersion time is 10 min), take it out and dry it at 80 °C for 30 min, anneal it at 150 °C for 10 min, and then immerse it in the ZnO growth solution with a concentration of 0.05 mol / L and grow it at 93 °C for 4 h to obtain glass fiber with a growth concentration of 0.05 mol / L and a one-dimensional nanostructured ZnO surface.

[0061] S6. Mix 60 g of bisphenol A epoxy resin, curing agent MTHPA, and accelerator DMP-30 evenly according to a mass ratio of 100∶80∶1 (which means the total mass of epoxy resin, curing agent, and accelerator is 60 g, the same hereinafter). After vacuum degassing, use it to infiltrate glass fibers, and place the glass fibers with a grown concentration of 0.05 mol / L of one-dimensional nano-ZnO structures on the outermost layer. After infiltration, hot press at 140 °C / 10 MPa and cure continuously at 120 °C for 10 h to obtain a glass fiber epoxy composite with a grown concentration of 0.05 mol / L of one-dimensional nano-ZnO structures on the nano surface (in this example, cut the purchased glass fibers into 20×10 cm, called "1 fiber cloth"; when preparing the glass fiber epoxy resin composite, select 4 fiber cloths. The middle two layers of fiber cloths in this example are unmodified glass fibers, and the outermost layer (i.e., the upper and lower layers) of fiber cloths are glass fibers with a grown concentration of 0.05 mol / L of one-dimensional nano-ZnO structures on the nano surface), denoted as #1.

[0062] Example 2

[0063] S1. Immerse the glass fibers in absolute ethanol and ultrasonically clean for 2 h to wash away the organic impurities on the fiber surface, and then dry in a vacuum oven at 80 °C for 12 h to obtain clean glass fibers;

[0064] S2. Adjust the pH of the hydrochloric acid dopamine solution with a concentration of 2 g / L to 8.5 using Tris, and then immerse 25 g of clean glass fibers in 1000 mL of the adjusted hydrochloric acid dopamine solution. Stir mechanically at room temperature for 12 h. After the reaction, wash 3 times with deionized water, and then dry in a vacuum oven at 40 °C for 24 h to obtain poly-dopamine pretreated glass fibers;

[0065] S3. Add 5.5 g of ZAD and 196.25 g of isopropanol to an oil bath pot, stir magnetically at 80 °C for 15 min, then add 2.55 g of triethylamine dropwise and continue stirring for 10 min. The solution gradually changes from turbid to clear, and then cool to room temperature and let stand for 3 h to obtain a ZnO seed solution;

[0066] S4. Mix equal volumes of a 0.1 mol / L zinc nitrate standard solution and a 0.1 mol / L HMTA standard solution, and stir well for 15 min to obtain a 0.1 mol / L ZnO growth solution;

[0067] S5. The glass fibers pretreated with polydopamine were first immersed in the ZnO seed solution (the immersion time was 10 min), taken out and dried at 80 °C for 30 min, annealed at 150 °C for 10 min, and then immersed in the ZnO growth solution with a concentration of 0.1 mol / L. After growing at 93 °C for 4 h, glass fibers with a concentration of 0.1 mol / L for constructing a one-dimensional nanostructure of ZnO can be obtained;

[0068] S6. 60 g of bisphenol A epoxy resin, the curing agent MTHPA and the accelerator DMP-30 were mixed and stirred evenly according to the mass ratio of 100∶80∶1. After vacuum degassing, the glass fibers were infiltrated with it, and the glass fibers with a concentration of 0.1 mol / L for constructing a one-dimensional nanostructure of ZnO were placed on the outermost layer. After infiltration, hot pressing was carried out at 140 °C / 10 MPa and continuously cured at 120 °C for 10 h, and then a glass fiber epoxy composite material with a one-dimensional nanostructure of ZnO constructed on the surface with a growth concentration of 0.1 mol / L can be obtained (in this example, the purchased glass fibers were cut into 20×10 cm, called "1 piece of fiber cloth"; when preparing the glass fiber epoxy resin composite material, 4 pieces of glass fiber cloth were selected. The middle two layers of fiber cloth in this example were unmodified glass fibers, and the outermost layer (i.e., the upper and lower layers) of fiber cloth was the glass fiber with a one-dimensional nanostructure of ZnO constructed on the nano surface with a growth concentration of 0.1 mol / L), denoted as #2.

[0069] Example 3

[0070] S1. The glass fibers were immersed in absolute ethanol and ultrasonically cleaned for 2 h to wash away the organic impurities on the fiber surface, and then dried in a vacuum oven at 80 °C for 12 h to obtain clean glass fibers;

[0071] S2. The pH of the hydrochloric acid dopamine solution with a concentration of 2 g / L was adjusted to 8.5 with Tris. Subsequently, 25 g of clean glass fibers were immersed in 1000 mL of the hydrochloric acid dopamine solution with the adjusted pH, and mechanically stirred at room temperature for 12 h. After the reaction ended, it was washed 3 times with deionized water, and then dried in a vacuum oven at 40 °C for 24 h to obtain polydopamine-pretreated glass fibers;

[0072] S3. 5.5 g of ZAD and 196.25 g of isopropanol were added to an oil bath pot, magnetically stirred at 80 °C for 15 min, and then 2.55 g of triethylamine was added dropwise and stirred for another 10 min. The solution gradually changed from turbid to clear, and then cooled to room temperature and allowed to stand for 3 h to obtain the ZnO seed solution;

[0073] S4. Equal volumes of a zinc nitrate standard solution with a concentration of 0.15 mol / L and an HMTA standard solution with a concentration of 0.15 mol / L were mixed and stirred thoroughly for 15 min to obtain a ZnO growth solution with a concentration of 0.15 mol / L;

[0074] S5. First, immerse the polydopamine-pretreated glass fiber into the ZnO seed solution (the immersion time is 10 min), take it out and dry it at 80 °C for 30 min, anneal it at 150 °C for 10 min, and then immerse it in the ZnO growth solution with a concentration of 0.1 mol / L. Grow it at 93 °C for 4 h to obtain glass fiber with a growth concentration of 0.15 mol / L for constructing a one-dimensional nanostructure of ZnO;

[0075] S6. Mix 60 g of bisphenol A epoxy resin, curing agent MTHPA and accelerator DMP-30 according to a mass ratio of 100:80:1 and stir evenly. After vacuum degassing, use it to infiltrate the glass fiber, and place the glass fiber with a growth concentration of 0.15 mol / L for constructing a one-dimensional nanostructure of ZnO on the outermost layer. After infiltration, hot press it at 140 °C / 10 MPa and cure it continuously at 120 °C for 10 h to obtain a glass fiber epoxy composite material with a one-dimensional nanostructure of ZnO constructed on the surface with a growth concentration of 0.15 mol / L (in this example, the purchased glass fiber is cut into 20×10 cm, called "1 piece of fiber cloth"; when preparing the glass fiber epoxy resin composite material, 4 pieces of glass fiber cloth are selected. The middle two layers of fiber cloth in this example are unmodified glass fiber, and the outermost layer (i.e., the upper and lower layers) of fiber cloth is glass fiber with a one-dimensional nanostructure of ZnO constructed on the surface with a growth concentration of 0.15 mol / L), denoted as #3.

[0076] Comparative Example 1

[0077] S1. Immerse the glass fiber into absolute ethanol and ultrasonically clean it for 2 h to wash away the organic impurities on the fiber surface, and then dry it in a vacuum oven at 80 °C for 12 h to obtain clean glass fiber;

[0078] S2. Mix 60 g of bisphenol A epoxy resin, curing agent MTHPA and accelerator DMP-30 according to a mass ratio of 100:80:1 (referring to the total mass of epoxy resin, curing agent and accelerator is 60 g), stir evenly after vacuum degassing, use it to infiltrate the glass fiber, hot press it at 140 °C / 10 MPa after infiltration, and cure it continuously at 120 °C for 10 h to obtain an unmodified glass fiber epoxy resin composite material (in this comparative example, the purchased glass fiber is cut into 20×10 cm, called "1 piece of fiber cloth"; when preparing the glass fiber epoxy resin composite material, all 4 pieces of glass fiber cloth are unmodified glass fiber, that is, the glass fiber used in this comparative example is all clean glass fiber), denoted as untreated GFRP composite material.

[0079] Figure 2 are the microscopic characterization results before and after constructing a one-dimensional nanostructure of ZnO on the glass fiber surface. Among them,Figure 2 (1) shows that the surface of the unmodified glass fiber is smooth and has no attachments. Figure 2 Figures (2)-(4) show that a large number of ZnO nanostructures (such as nanoneedles, nanowires, and nanorods) are distributed on the surface of the glass fiber, and as the growth concentration increases, the surface roughness of the glass fiber increases and the number of nano-ZnO one-dimensional structures increases significantly.

[0080] Figure 3 This is a schematic diagram of the DC flashover test platform for glass fiber epoxy composites with a one-dimensional nano-ZnO structure on the surface. It is mainly composed of a stainless steel experimental chamber (programmable constant temperature and humidity test chamber), a negative polarity high-voltage DC power supply (output range is 0-50kV), a current measurement coil (Pearson, Model 6585, 1V / A), a high-voltage attenuation probe, an oscilloscope and other devices. The finger-shaped electrodes in the flashover platform can simulate the extremely uneven electric field in which insulating devices such as composite insulators are located. One of the needle-shaped electrodes is connected to a conductive device that passes through the chamber, which is connected in series with the power supply through a protective resistor. The other needle electrode is grounded together with the chamber, and the distance between the two needles is kept at 5mm.

[0081] The test method is as follows: ultrasonically clean the composite sample (i.e., a glass fiber epoxy composite material with a one-dimensional structure of nano ZnO on the surface, the same below) for 1 minute and place it on the sample stage of the cavity after drying. Adjust the position of the sample stage so that the two electrodes are located in the center of the sample and in good contact with the surface of the sample. Boost the voltage from zero potential at a rate of 100V / s until surface flashover occurs. The flashover is accompanied by a blue arc and a sharp discharge sound. The flashover voltage is read with a high-voltage attenuation probe and an oscilloscope. The oscilloscope can capture the voltage value and voltage waveform at the moment of surface flashover through edge triggering and record them. Disconnect the power supply immediately after each flashover occurs, and then increase the voltage from zero potential after an interval of 10 minutes for the next test. In order to reduce the error, 15 tests are performed on each sample, and the average value is taken as the flashover voltage of the sample.

[0082] Figure 4Schematic diagram of the charge dissipation test platform for glass fiber epoxy composites with one-dimensional nanostructured ZnO on the surface, mainly composed of a negative high-voltage DC power supply, a corona needle, an active capacitance probe (Trek 3455ET), an electrometer (Trek P0865, 10 kV), a data acquisition card (Altaite USB3202), a supporting computer, etc. The test method is as follows: After ultrasonic cleaning the composite sample for 1 min and drying it, place it on the sample stage. Adjust the needle electrode so that it is 5 mm above the sample. Adjust the output voltage of the high-voltage DC source to 7 kV and corona charge the sample for 1 min. After charging, quickly place the sample 2 mm below the active capacitance probe using a two-dimensional moving platform. Move the probe to align with the charging position of the needle electrode, then turn on the acquisition card and start the surface potential test program. Set the sampling frequency to 0.01 kHz and start single-point continuous acquisition of data, collecting the potential data from 0 to 30 min after the end of charging. Plotting the potential data against the corresponding time can obtain the exponential surface potential decay function curve of the sample.

[0083] Figure 5 Schematic diagram of the breakdown field strength test platform for glass fiber epoxy composites with one-dimensional nanostructured ZnO on the surface, including an AC step-up vehicle, a protective resistor, a voltage divider, an oil cup, spherical electrodes, etc. To reduce partial discharge and prevent surface discharge, the test sample and the ball-ball electrodes are both immersed in insulating oil. Increase the voltage uniformly at a speed of 1 kV / s. At the moment of breakdown, there is an orange spark, the transformer issues a short-circuit alarm and the current relay trips. Read the peak voltage at the moment of breakdown as the breakdown voltage of this experiment. Select 10 different points on each sample for breakdown experiments. Considering the slight difference in thickness at different points of the composite material, in the present invention, the breakdown voltage is divided by the thickness of this point as the breakdown field strength.

[0084] Figure 6 Flashover voltage test results of glass fiber epoxy composites with one-dimensional nanostructured ZnO on the surface in Examples 1 - 3 and untreated GFRP composites in Comparative Example 1. The image shows that the flashover voltage of the untreated GFRP composites in Comparative Example 1 is 8.12 kV. After the ZnO one-dimensional nanostructure on the glass fiber surface, the flashover voltage increases to varying degrees, and with the increase of the growth concentration, the flashover voltage of the GFRP composites gradually increases. When the growth concentration is 0.05 mol / L, the flashover voltage is 9.1 kV, which is a 12.06% increase compared to the unmodified GFRP; when the growth concentration is 0.1 mol / L (i.e., Example 2), the flashover voltage is 9.9 kV, an increase of 21.9%; when the growth concentration is 0.15 mol / L (i.e., Example 3), the flashover voltage is 10.2 kV, an increase of 25.61%. With the increase of the growth concentration, the increase amplitude of the GFRP flashover voltage gradually decreases, indicating that there is an optimal growth concentration.

[0085] Figure 7 Charge dissipation test results of the glass fiber epoxy composite with one-dimensional nano-ZnO structures constructed on the surface in Examples 1-3 and the untreated GFRP composite in Comparative Example 1. It can be seen that the untreated GFRP composite in Comparative Example 1 dissipated about 30% during the test time. When one-dimensional nano-ZnO structures were constructed, the charge dissipation rate of the GFRP composite slowed down slightly. When the growth concentration was 0.05 mol / L, the charge dissipated about 20%; when the growth concentration was 0.1 mol / L, the charge dissipated about 16%; when the growth concentration was 0.15 mol / L, the charge dissipated about 10%. Constructing one-dimensional nano-ZnO structures can avoid the rapid transport of surface charges on GFRP, thereby enhancing the surface flashover voltage of the composite material.

[0086] Figure 8 Breakdown field strength test results of the glass fiber epoxy composite with one-dimensional nano-ZnO structures constructed on the surface in Examples 1-3 and the untreated GFRP composite in Comparative Example 1. The breakdown field strength of the untreated GFRP composite in Comparative Example 1 was 34.70 kV / mm. After modification with one-dimensional nano-ZnO structures, the breakdown field strength of the glass fiber composite increased to varying degrees. When the growth concentration was 0.05 mol / L, the breakdown field strength was 48.7 kV / mm, an increase of 40.34% compared to the unmodified GFRP; when the growth concentration was 0.1 mol / L, the breakdown field strength was 53 kV / mm, an increase of 52.7%; when the growth concentration was 0.15 mol / L, the breakdown field strength was 54.2 kV / mm, an increase of 56.19%.

[0087] In summary, the present invention provides a method for constructing one-dimensional nano-ZnO structures to improve the insulation performance of glass fiber epoxy composites. Through the surface treatment with polydopamine, a secondary reaction platform is formed on the surface of the glass fiber, and thus one-dimensional nano-ZnO structures are successfully constructed on the surface of the glass fiber, which can effectively regulate the charge dissipation rate, thereby alleviating the distortion of the surface electric field strength and increasing the surface flashover voltage. The method for preparing the fiber-reinforced epoxy composite provided by the present invention can effectively increase its surface flashover voltage. The treatment means used can achieve industrial batch preparation, and this method is also applicable to other types of thermosetting polymers, fiber fabrics, and nanofiber materials.

[0088] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials, characterized in that: Firstly, a film structure is formed on the surface of glass fiber by utilizing the polymerization reaction of dopamine to obtain glass fiber pretreated with polydopamine; then, nano ZnO is constructed on the surface of the glass fiber pretreated with polydopamine to obtain glass fiber with a one-dimensional structure of nano ZnO on the surface; finally, the glass fiber with a one-dimensional structure of nano ZnO on the surface is compounded with epoxy resin.

2. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 1, characterized in that: Before forming a membrane structure on the surface of the glass fiber by utilizing the polymerization reaction of dopamine, a pretreatment process of cleaning and drying the glass fiber is also included.

3. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 1, characterized in that: The preparation steps of the polydopamine pretreated glass fiber are: immersing the glass fiber in an alkaline dopamine hydrochloride solution, stirring, washing with water, and drying to obtain the polydopamine pretreated glass fiber.

4. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 3, characterized in that: The preparation step of the alkaline dopamine hydrochloride solution is: adjusting the pH of the dopamine hydrochloride solution to alkaline with tris(hydroxymethyl)aminomethane to obtain the alkaline dopamine hydrochloride solution.

5. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 1, characterized in that: The step of constructing nano ZnO on the surface of the polydopamine pretreated glass fiber is: immersing the polydopamine pretreated glass fiber into a ZnO seed solution, drying and annealing, and then immersing it in a ZnO growth solution for growth to obtain a glass fiber with a one-dimensional nano ZnO structure on the surface.

6. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 5, characterized in that: The preparation steps of the ZnO seed solution are: mixing zinc acetate dihydrate and isopropanol, stirring evenly, adding triethylamine, and stirring evenly again to obtain the ZnO seed solution.

7. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 5, characterized in that: The preparation step of the ZnO growth solution is: uniformly mixing a zinc nitrate standard solution and a hexamethylenetetramine solution to obtain a ZnO growth solution.

8. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 7, characterized in that: The ZnO concentration in the ZnO growth solution is 0.05-0.15 mol / L.

9. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 8, characterized in that: The ZnO concentration in the ZnO growth solution is 0.05 mol / L, 0.1 mol / L or 0.15 mol / L.

10. The method for constructing a one-dimensional nano ZnO structure to improve the insulation performance of glass fiber epoxy composite materials according to claim 1, characterized in that: The steps of preparing the glass fiber and epoxy resin composite material with the surface constructed of nano ZnO one-dimensional structure are as follows: epoxy resin, curing agent and accelerator are mixed, and the glass fiber is impregnated after vacuum degassing, wherein the glass fiber with the nano ZnO one-dimensional structure is located at the outermost layer, and hot pressing is performed after impregnation and solidification.

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