PVA fiber nano-ZnO / epoxy resin composite material and preparation method thereof

Abstract

The application provides a PVA fiber / nano ZnO / epoxy resin composite material and a preparation method thereof, the preparation method is that polyvinyl alcohol fiber, polyvinyl alcohol solution and nano ZnO dispersion liquid are stirred and mixed, then mixed with epoxy resin and other conventional additives by using a vacuum assisted resin transfer molding (VARTM) process, and the PVA fiber / nano ZnO / epoxy resin composite material is prepared. It is found that under the condition of the vacuum assisted resin transfer molding (VARTM) process, through the synergistic effect of the PVA fiber, the PVA solution and the nano ZnO dispersion liquid, the mechanical interlocking between the treated PVA fiber and the epoxy resin matrix is realized, and the strength of the PVA reinforced epoxy resin material is further improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fiber reinforced epoxy resin composites, and relates to a PVA fiber / nano ZnO / epoxy resin composite material and a preparation method thereof, in particular to a PVA fiber / nano ZnO / epoxy resin composite material prepared by using a vacuum assisted resin transfer molding (VARTM) process. BACKGROUND

[0002] Polyvinyl alcohol fiber (PVA fiber for short) is a synthetic fiber prepared from polyvinyl alcohol (PVA) as raw material. The PVA fiber has the characteristics of high strength, high modulus, acid and alkali resistance, and good weather resistance, and its strong polar structure of multiple hydroxyl groups has good chemical compatibility and high interfacial adhesion strength with the composite material, and is an ideal fiber for fiber reinforced composites.

[0003] Fiber reinforced epoxy resin matrix composite (FRP) is a material with excellent comprehensive performance prepared by using epoxy resin as matrix and reinforcing fiber as reinforcing body through hot pressing molding. Traditional reinforcing fibers are generally glass fibers and carbon fibers. These fibers have high strength and rough surface, and have strong interaction with epoxy resin. With the rapid development of new energy field, wind energy as one of the important clean energies has received widespread attention. As the load-bearing structure of wind power blades, the large-scale and lightweight of FRP have become the most important development trend. Glass fibers have large density, and the weight of FRP made of glass fibers is difficult to reduce; carbon fibers have high cost, and therefore are difficult to be applied to the entire large-scale wind power blades (especially hundreds of meters). Organic fibers have strong performance and low density, and are expected to be applied to FRP. At present, the organic fiber reinforced epoxy resin matrix composite (OFRP) mainly uses high-performance fibers such as aramid fibers and polyimide fibers. Due to the high cost, these fibers are difficult to be applied in industry. Polyvinyl alcohol (PVA) fiber has the characteristics of low density, high specific strength and specific stiffness, and low cost. Compared with other organic fibers, PVA fiber has more hydroxyl groups on the surface as reaction sites, and the interaction between PVA fiber and epoxy resin matrix is stronger in theory; PVA fiber is easier to be further modified due to the presence of hydroxyl groups. In summary, the use of PVA fiber to prepare FRP has certain practical significance for the large-scale and lightweight of composites.

[0004] As described above, compared with traditional reinforcing fibers (such as glass fibers and carbon fibers), polyvinyl alcohol fiber has the advantages of lightweight, high specific strength and low cost, but in actual industrialization, the strength of polyvinyl alcohol fiber cannot be compared with that of glass fiber, and therefore there is no related report on the application of polyvinyl alcohol fiber in the current application field of large-scale parts (such as wind power blades) with high material strength requirements.

[0005] In order to play the light weight advantage of polyvinyl alcohol fiber and make it adapt to the mechanical properties of the target part, the currently recognized way is to improve the polymerization degree of polyvinyl alcohol. Compared with low polymerization degree polyvinyl alcohol, high polymerization degree polyvinyl alcohol has less macromolecular end group, thereby reducing the crystallization defects of macromolecules, improving the crystallinity and the binding force between macromolecules, and thus can significantly improve the strength of polyvinyl alcohol fiber.

[0006] At present, the preparation methods of polyvinyl alcohol mainly include solution polymerization, bulk polymerization, suspension polymerization and emulsion polymerization. However, bulk polymerization, suspension polymerization and emulsion polymerization have not been generally industrialized due to high cost; the current industrialized production of polyvinyl alcohol mainly adopts solution polymerization method, but the polymerization degree of the obtained polyvinyl alcohol is not more than 3000.

[0007] Therefore, based on the low-cost polyvinyl alcohol that can be purchased on the market at present, the upper limit of the strength of the fiber reinforced composite material prepared by using the same is obviously limited, which greatly restricts the application field and market positioning thereof. SUMMARY

[0008] In order to solve the above problems in the prior art, the present application provides a PVA fiber@ nano ZnO / epoxy resin composite material and a preparation method thereof. It is found that under the condition of vacuum assisted resin transfer molding (VARTM) process, through the synergistic effect of PVA fiber, PVA solution and nano ZnO dispersion liquid, mechanical interlocking between the treated PVA fiber and the epoxy resin matrix is realized, and the strength of the PVA reinforced epoxy resin material is further significantly improved.

[0009] In order to achieve the above purpose, the present application is realized by adopting the following technical measures.

[0010] In one aspect, the present application provides a preparation method of a PVA fiber@ nano ZnO / epoxy resin composite material, mainly including the following steps:

[0011] (1) The raw materials mainly including the following components are mixed according to the mass fraction to prepare materials, as a mixture:

[0012] Polyvinyl alcohol fiber (PVA fiber) 2-4 parts,

[0013] Polyvinyl alcohol solution 1000-1200 parts,

[0014] Nano ZnO dispersion liquid 100-150 parts;

[0015] The mass concentration of the polyvinyl alcohol solution is 5-10wt%,

[0016] The mass concentration of the nano ZnO dispersion liquid is 30-40wt%.

[0017] (2) The mixture prepared in step (1) is placed under stirring or ultrasonic conditions for 4-6 h, and then the treated polyvinyl alcohol fibers are filtered out, washed and dried for standby use;

[0018] (3) The treated polyvinyl alcohol fibers obtained in step (2) are mixed with epoxy resin and other conventional additives by vacuum assisted resin transfer molding (VARTM) process to prepare PVA fiber / nano-ZnO / epoxy resin composite material; wherein the process conditions of the vacuum assisted resin transfer molding (VARTM) process are as follows: the temperature is set at 60-160°C, the vacuum degree is maintained at 0.06-0.1 MPa for 4-8 h.

[0019] In this article, the polyvinyl alcohol fibers (PVA fibers) in step (1) can be conventional commercially available polyvinyl alcohol fiber raw materials, or can be self-made by those skilled in the art according to the existing technology using commercially available polyvinyl alcohol spinning.

[0020] In one of the technical solutions, in order to further improve the strength of the final product and obtain a composite material with consistent strength as the embodiment of the present application, the polyvinyl alcohol fibers in step (1) are preferably polyvinyl alcohol fibers with a density of 1.1-1.3 g / cm 3 , a stretching ratio of 5-10 times, an orientation degree of 94-98%, and a tensile strength of 285-500 MPa.

[0021] The above-mentioned polyvinyl alcohol fibers with a density of 1.1-1.3 g / cm 3 , a stretching ratio of 5-10 times, an orientation degree of 94-98%, and a tensile strength of 285-500 MPa can be obtained by referring to the process method described in the existing technical literature (Qin, Q. E., Zhou, T., Wang, M., Li, L. & Chen, N. Structure evolution and performance of poly(vinyl alcohol) fibers with controllable cross-section fabricated using a combination of melt-spinning and stretching. Polymer Testing 117, doi:10.1016 / j.polymertesting.2022.107867 (2023.)).

[0022] In order to better illustrate the present application, and to provide a preferred technical solution for reference, the polyvinyl alcohol fiber is prepared by the following process: the polyvinyl alcohol powder with a polymerization degree of 1700±50 and an alcoholysis degree of 88% is plasticized and modified by using water with a polyvinyl alcohol content of 40%, and the polyvinyl alcohol fiber is prepared by using the plasticized and modified polyvinyl alcohol by using a conventional polyvinyl alcohol melt spinning device; wherein the process parameters of the polyvinyl alcohol melt spinning device are: the screw three-stage temperature is 80-90℃, 145-160℃, and 150-165℃, respectively, the spinneret temperature is 125-130℃, the spinneret micropore equivalent diameter is 0.3mm, and the draw ratio is 5-10 times. The above-mentioned process parameters not mentioned above can use conventional process parameters, and further can preferably use the self-made polyvinyl alcohol melt spinning device recorded in the above-mentioned document.

[0023] It should be additionally explained that the commercially available and self-made polyvinyl alcohol fiber, when used as a raw material to prepare a fiber reinforced epoxy resin composite material, further comprises a pretreatment of the polyvinyl alcohol fiber in a conventional process to reduce the mixing of impurities, for example, the polyvinyl alcohol fiber can be cleaned by using an organic reagent (for example, a mixture of acetone and ethanol), and dried at 50℃ for 2-4h.

[0024] In this document, the polyvinyl alcohol solution in step (1) is a polyvinyl alcohol solution with a mass concentration of 5-10wt%, and the solvent can be an organic solvent or deionized water, and when the solvent is an organic solvent, it should be able to fully dissolve 5-10wt% of polyvinyl alcohol at room temperature.

[0025] In one of the technical solutions, in order to reduce the cost, the polyvinyl alcohol solution in step (1) is a polyvinyl alcohol aqueous solution.

[0026] In this document, the nano-ZnO dispersion liquid in step (1) is to fully disperse the nano-ZnO powder in a solvent, because it is found by experiment that directly adding nano-ZnO powder to the polyvinyl alcohol solution can easily cause serious agglomeration of the nano-ZnO powder and is difficult to disperse, so it is necessary to pre-disperse the nano-ZnO.

[0027] In this document, the nano-ZnO dispersion liquid in step (1) is a nano-ZnO dispersion liquid with a mass concentration of 30-40wt%, and the solvent is a conventional organic solvent used in the prior art for preparing a ZnO dispersion liquid, for example, 1,2-propanediol monomethyl ether acetate, isooctyl ester, Tween 60, Span 80, etc.

[0028] In one of the technical solutions, the solvent of the nano-ZnO dispersion liquid in step (1) is 1,2-propanediol monomethyl ether acetate.

[0029] In the present text, the vacuum assisted resin transfer molding (VARTM) process in step (3) is a process matched with a vacuum assisted resin transfer molding machine. The specific process operation can refer to the existing technology or the description in the instruction manual of the used vacuum assisted resin transfer molding machine.

[0030] In order to better illustrate the present application, and provide a technical solution for reference, the vacuum assisted resin transfer molding (VARTM) process in step (3) is as follows: the flow guide net, release cloth, treated polyvinyl alcohol fiber, release cloth and flow guide net are sequentially placed as materials on the hot table, the glue injection seat is placed at both ends of the hot table, the spiral pipe is laid between the glue injection seat and the polyvinyl alcohol fiber and around the materials, and then the materials placed above the hot table are sealed; the holes are drilled on the glue injection seats at both ends to connect the hoses, one end of the hose flows into the mixture of epoxy resin and other conventional additives, and the other end of the hose is connected with a vacuum pump and a redundant resin collector.

[0031] In the present text, the epoxy resin in step (3) is the type and model of epoxy resin commonly used in fiber reinforced epoxy resin composites in the technical field.

[0032] In one of the technical solutions, the epoxy resin in step (3) is preferably a bisphenol A type epoxy resin or a phenolic type epoxy resin.

[0033] In the present text, the other conventional additives in step (3) are the additives commonly used in fiber reinforced epoxy resin composites in the technical field, such as the selection of conventional additives including diluents, curing agents, crosslinking catalysts, etc. It should be noted that fiber reinforced epoxy resin composites in the prior art are materials with a relatively mature chemical preparation system, so the additives (including diluents, curing agents, crosslinking catalysts) used in their process and the addition amount of the additives should be the common knowledge known to those skilled in the art, and further preferably the additives and the addition amount of the additives commonly used in the vacuum assisted resin transfer molding (VARTM) process.

[0034] In order to better illustrate the present application, and provide a technical solution for reference, the other conventional additives in step (3) include 10-20 wt% ethylene glycol diglycidyl ether or epoxy chloropropane, 20-30 wt% phthalic anhydride or 4,4-diamino diphenyl methane, and 0.05-0.1 wt% 2-ethyl-4-methyl imidazole, based on the mass percentage of epoxy resin.

[0035] It is additionally noted that, in order to ensure the sufficient mixing of the other conventional additives with the epoxy resin in step (3), it is generally preferred to mix the other conventional additives with the epoxy resin by stirring sufficiently, for example, at a temperature of 70-90°C.

[0036] In the present application, the stirring, washing and drying are all in accordance with the conventional principles in chemical processes, and the skilled in the art can perform the specific operations according to the common knowledge.

[0037] In another aspect, the present application provides the PVA fiber@ nano-ZnO / epoxy resin composite prepared by the above preparation method.

[0038] The PVA fiber@ nano-ZnO / epoxy resin composite can be used as a lightweight composite material to prepare large parts, such as large composite laminates as structural materials.

[0039] The present application has the following advantages:

[0040] 1. In the technical scheme of the present application, it is found that, under the condition of using the vacuum assisted resin transfer molding (VARTM) process, the treated PVA fiber and the epoxy resin matrix are mechanically interlocked through the synergistic effect of the PVA fiber, the PVA solution and the nano-ZnO dispersion liquid, which further improves the strength of the PVA reinforced epoxy resin material.

[0041] 2. In the technical scheme of the present application, it is found through comparative experiments that the treated polyvinyl alcohol fiber has better mechanical properties than the similar treatment scheme, which confirms that the PVA fiber and the epoxy resin matrix are mechanically interlocked.

[0042] 3. In the technical scheme of the present application, commercially available polyvinyl alcohol can be used to take advantage of the lightweight of polyvinyl alcohol fiber and adapt to the mechanical properties of the target part, which further expands the application range of the prepared PVA reinforced epoxy resin material.

[0043] DRAWINGS

[0044] Figure 1 The process schematic diagram for preparing the PVA fiber@ nano-ZnO / epoxy resin composite by using the vacuum assisted resin transfer molding process in Example 1 of the present application.

[0045] Figure 2SEM images of the treated polyvinyl alcohol fibers obtained in step (2) of Example 1 and Comparative Examples 1-2. (a) and (b) are the treated polyvinyl alcohol fibers obtained in step (2) of Example 1; (c) is the treated polyvinyl alcohol fibers obtained in step (2) of Comparative Example 1; (d) is the treated polyvinyl alcohol fibers obtained in step (2) of Comparative Example 2. It is clear that only the treated polyvinyl alcohol fibers in Example 1 can successfully coat the nano-ZnO particles, indicating that the PVA solution plays a crucial role in the system, improving the interaction between the PVA fibers and the nano-ZnO particles, so that the nano-ZnO particles act as "anchors" to connect the PVA fibers and the epoxy matrix, improving the mechanical properties of the composite material.

[0046] Figure 3 AFM images of the treated polyvinyl alcohol fibers obtained in step (2) of Example 1 and Comparative Examples 1-2. (a) is the treated polyvinyl alcohol fibers obtained in step (2) of Example 1; (b) is the treated polyvinyl alcohol fibers obtained in step (2) of Comparative Example 1; (c) is the treated polyvinyl alcohol fibers obtained in step (2) of Comparative Example 2. It is clear that the treated polyvinyl alcohol fibers in Comparative Examples 1 and 2 have relatively smooth surfaces and low roughness; while the treated polyvinyl alcohol fibers in Example 1 have significantly improved surface roughness due to the successful coating of nano-ZnO particles, providing conditions for the interfacial locking between the epoxy resin matrix and the PVA fibers. DETAILED DESCRIPTION

[0047] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations on the claims of the present application. Those skilled in the art can modify the process parameters as appropriate based on the content herein. It should be particularly pointed out that all similar substitutions and modifications are obvious to those skilled in the art, and they are considered to be included in the present application. The methods and applications of the present application have been described by the preferred embodiments, and those skilled in the art can obviously modify or appropriately change and combine the methods and applications described herein to realize and apply the present application technology without departing from the content, spirit and scope of the present application. Although it is believed that those skilled in the art have a full understanding of the following terms, the following definitions are stated to facilitate the description of the subject matter disclosed in the present application.

[0048] In one aspect, the present application provides a method for preparing a PVA fiber@nano-ZnO / epoxy resin composite material, mainly comprising the following steps:

[0049] (1) Mix the raw materials mainly comprising the following components by mass fraction to prepare the mixture as the mixing material:

[0050] Polyvinyl alcohol fiber (PVA fiber) 2-4 parts,

[0051] Polyvinyl alcohol solution 1000-1200 parts,

[0052] Nano-ZnO dispersion liquid 100-150 parts;

[0053] The mass concentration of the polyvinyl alcohol solution is 5-10 wt%,

[0054] The mass concentration of the nano-ZnO dispersion liquid is 30-40 wt%;

[0055] (2) The mixture prepared in step (1) is placed and treated under stirring or ultrasonic conditions for 4-6 h, and then the treated polyvinyl alcohol fiber is filtered out, washed and dried for standby use;

[0056] (3) The treated polyvinyl alcohol fiber obtained in step (2) is mixed with epoxy resin and other conventional additives by vacuum-assisted resin transfer molding (VARTM) process to prepare PVA fiber@nano-ZnO / epoxy resin composite material; wherein the process conditions of the vacuum-assisted resin transfer molding (VARTM) process are as follows: the temperature is set at 60-160℃, the vacuum degree is maintained at 0.06-0.1 MPa for 4-8 h.

[0057] In one embodiment, the polyvinyl alcohol fiber (PVA fiber) in step (1) can be a conventional commercially available polyvinyl alcohol fiber raw material, or can be self-made by a person skilled in the art according to the existing technology using commercially available polyvinyl alcohol spinning.

[0058] In one embodiment, in order to further improve the strength of the final product and obtain a composite material with consistent strength as the embodiment of the present application, the polyvinyl alcohol fiber in step (1) is preferably a polyvinyl alcohol fiber with a density of 1.1-1.3 g / cm 3 , a stretching ratio of 5-10 times, an orientation degree of 94-98%, and a tensile strength of 285-500 MPa.

[0059] The above is preferably a polyvinyl alcohol fiber with a density of 1.1-1.3 g / cm 3, 5-10 times of stretch ratio, degree of orientation 94-98%, tensile strength 285-500 MPa polyvinyl alcohol fibers can be obtained by the process method described in the prior art literature (Qin, Q. E., Zhou, T., Wang, M., Li, L. & Chen, N. Structure evolution and performance of poly(vinyl alcohol) fibers with controllable cross-section fabricated using a combination of melt-spinning and stretching. Polymer Testing 117, doi:10.1016 / j.polymertesting.2022.107867 (2023).).

[0060] In order to better illustrate the present application, and to provide a preferred embodiment for reference, the polyvinyl alcohol fiber is prepared by the following process: polyvinyl alcohol powder with a degree of polymerization of 1700±50 and an alcoholysis degree of 88% is plasticized and modified with water at a weight of 40% of polyvinyl alcohol, and the polyvinyl alcohol fiber is prepared by using conventional polyvinyl alcohol melt spinning equipment after plasticization and modification; wherein the process parameters of the polyvinyl alcohol melt spinning equipment are: the screw three-stage temperature is 80-90℃, 145-160℃, 150-165℃ respectively, the spinneret temperature is 125-130℃, the micro-pore equivalent diameter of the spinneret is 0.3mm, and the stretch ratio is 5-10 times. The above-mentioned process parameters not mentioned can use conventional process parameters, and further can preferably use the self-made polyvinyl alcohol melt spinning equipment described in the above-mentioned literature.

[0061] It should be additionally pointed out that commercially available and self-made polyvinyl alcohol fibers, when used as raw materials to prepare fiber reinforced epoxy resin composites, also include pretreatment of polyvinyl alcohol fibers in conventional processes to reduce the mixing of impurities. In one embodiment, for example, the polyvinyl alcohol fiber can be cleaned with an organic reagent (such as a mixture of acetone and ethanol), and dried at 50℃ for 2-4h.

[0062] In one embodiment, the polyvinyl alcohol solution in step (1) is a polyvinyl alcohol solution with a mass concentration of 5-10 wt%, and the solvent can be an organic solvent or deionized water. When the solvent is an organic solvent, it should be able to fully dissolve 5-10 wt% of polyvinyl alcohol at room temperature. In one embodiment, the polyvinyl alcohol solution in step (1) is a polyvinyl alcohol solution with a mass concentration of 5-10 wt%, for example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any range or point value therebetween.

[0063] In one embodiment, the polyvinyl alcohol solution in step (1) is a polyvinyl alcohol aqueous solution to reduce cost.

[0064] In this embodiment, the nano-ZnO dispersion liquid in step (1) is prepared by dispersing nano-ZnO powder in a solvent. It is found through experiments that directly adding nano-ZnO powder to the polyvinyl alcohol solution can cause serious agglomeration of the nano-ZnO powder and make it difficult to disperse. Therefore, it is necessary to pre-disperse the nano-ZnO powder.

[0065] In one embodiment, the nano-ZnO dispersion liquid in step (1) has a mass concentration of 30-40 wt%, and the solvent is a conventional organic solvent used in the prior art for preparing ZnO dispersion liquids, such as 1,2-propanediol monomethyl ether acetate, isooctyl ester, Tween 60, Span 80, etc. In one embodiment, the nano-ZnO dispersion liquid in step (1) has a mass concentration of 30-40 wt%, for example, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, or any range or point value therebetween.

[0066] In one embodiment, the solvent of the nano-ZnO dispersion liquid in step (1) is 1,2-propanediol monomethyl ether acetate.

[0067] In one embodiment, the polyvinyl alcohol fiber (PVA fiber) in step (1) is 2-4 parts, for example, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, or any range or point value therebetween; the polyvinyl alcohol solution is 1000-1200 parts, for example, 1000 parts, 1010 parts, 1020 parts, 1030 parts, 1040 parts, 1050 parts, 1060 parts, 1070 parts, 1080 parts, 1090 parts, 1100 parts, 1110 parts, 1120 parts, 1130 parts, 1140 parts, 1150 parts, 1160 parts, 1170 parts, 1180 parts, 1190 parts, 1200 parts, or any range or point value therebetween; and the nano-ZnO dispersion liquid is 100-150 parts, for example, 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, or any range or point value therebetween.

[0068] In this context, the vacuum assisted resin transfer molding (VARTM) process in step (3) is a process matched with a vacuum assisted resin transfer molding machine, and the specific process operation can be referred to the prior art or the description in the instruction manual of the used vacuum assisted resin transfer molding machine.

[0069] In order to better illustrate the present application and provide a reference embodiment, the vacuum assisted resin transfer molding (VARTM) process in step (3) is as follows: the flow guide net, release cloth, treated polyvinyl alcohol fiber, release cloth, and flow guide net are sequentially placed as materials on a hot table, the glue injection seats are placed at both ends of the hot table, the spiral tubes are laid between the glue injection seats and the polyvinyl alcohol fiber and around the materials, and then the materials placed on the hot table are sealed; the holes are drilled on the glue injection seats at both ends to connect the hoses, one end of the hose flows into the mixture of epoxy resin and other conventional additives, and the other end of the hose is connected to the vacuum pump and the excess resin collector.

[0070] In this context, the epoxy resin in step (3) is the type and model of epoxy resin commonly used in fiber-reinforced epoxy resin composite materials in the technical field.

[0071] In one embodiment, the epoxy resin in step (3) is preferably a bisphenol A type epoxy resin or a phenolic type epoxy resin.

[0072] In one embodiment, the other conventional additives in step (3) are selected from the group consisting of diluents, curing agents, cross-linking catalysts and the like conventional additives used in the art of fiber reinforced epoxy resin composites. It is noted that fiber reinforced epoxy resin composites are well known in the art and have been prepared using well known chemical processes. Therefore, the additives (including diluents, curing agents, cross-linking catalysts) and the amounts of the additives used in the process are well known to those skilled in the art. Further, the additives and the amounts of the additives used in the vacuum assisted resin transfer molding (VARTM) process are preferred.

[0073] To better illustrate the present application and to provide an embodiment for reference, the other conventional additives in step (3) include 10-20 wt% of ethylene glycol diglycidyl ether or epichlorohydrin, such as 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, or any range or point value therebetween; 20-30 wt% of phthalic anhydride or 4,4-diaminodiphenyl methane, such as 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, or any range or point value therebetween; and 0.05-0.1 wt% of 2-ethyl-4-methylimidazole, such as 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, or any range or point value therebetween, based on the weight of the epoxy resin.

[0074] It is noted that to ensure the other conventional additives in step (3) are well mixed with the epoxy resin, the other conventional additives and the epoxy resin are usually well stirred to form a mixture. For example, the other conventional additives and the epoxy resin are well mixed at a temperature of 70-90 °C.

[0075] In one embodiment, the process conditions of the vacuum assisted resin transfer molding (VARTM) process in step (3) are: a temperature of 60-160°C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, or any range or point value therebetween; a vacuum of 0.06-0.1 MPa, for example 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.1 MPa, or any range or point value therebetween; and a processing time of 4-8 h, for example 4 h, 5 h, 6 h, 7 h, 8 h, or any range or point value therebetween.

[0076] In this context, the stirring, washing, and drying all follow the conventional principles in chemical processes, and the skilled person can perform the specific operations according to common knowledge.

[0077] In another aspect, the present application provides the PVA fiber@nano-ZnO / epoxy resin composite prepared by the above preparation method.

[0078] The PVA fiber@nano-ZnO / epoxy resin composite described above can be used as a lightweight composite material to prepare large parts, such as large composite laminates.

[0079] The present application will be further explained in detail below with reference to examples. However, those skilled in the art will understand that these examples are provided only for illustrative purposes, and are not intended to limit the scope of the present application.

[0080] Examples

[0081] The embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only for the purpose of illustration, and should not be considered as limiting the scope of the present application. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagent or instrument is specified, it is a conventional product that can be obtained by purchase. The present application should not be interpreted as being limited to the specific examples described.

[0082] 1. Raw materials

[0083] Polyvinyl alcohol powder, degree of polymerization 1700±50, alcoholysis degree 88%, Chongqing Chuanwei Petrochemical Engineering Co., Ltd.;

[0084] Nano-ZnO dispersion, 50-90 nm, solid content 30 wt%, 1,2-propanediol monomethyl ether acetate as solvent;

[0085] Anhydrous ethanol, effective content ≥99.7%, analytical pure, Shanghai Fine Chemical Reagent Co., Ltd.;

[0086] Acetone, effective content ≥ 99.5%, analytical pure, Sichuan Xilong Science Co., Ltd.;

[0087] Epoxy resin (EP-128), Chengdu Kaimite Technology Co., Ltd., epoxy value 0.51 Eq / 100g;

[0088] Ethylene glycol diglycidyl ether, Cool Chemical Technology (Beijing) Co., Ltd.;

[0089] 4,4-diaminodiphenyl methane, analytical pure, Aladdin Reagent Co., Ltd.;

[0090] 2-ethyl-4-methylimidazole, analytical pure, Aladdin Reagent Co., Ltd.

[0091] 2. Preparation method

[0092] The polyvinyl alcohol fiber is prepared by using the polyvinyl alcohol powder with a polymerization degree of 1700±50 and an alcoholysis degree of 88% and plasticizing modification with water in an amount of 40% of the weight of the polyvinyl alcohol, and using a conventional polyvinyl alcohol melt spinning device; wherein the process parameters of the polyvinyl alcohol melt spinning device are as follows: the screw three-stage temperature is 80-90℃, 145-160℃ and 150-165℃ respectively, the spinneret temperature is 125-130℃, the micro-hole equivalent diameter of the spinneret is 0.3mm, and the draw ratio is 5 times.

[0093] The polyvinyl alcohol fiber with a density of 1.3g / cm 3 , a draw ratio of 5 times, and an orientation degree of 94% and a tensile strength of 385MPa is prepared by melt spinning.

[0094] Before use, the prepared polyvinyl alcohol fiber is cleaned with a mixture of acetone and ethanol, and dried at a temperature of 50℃ for 2-4h;

[0095] (1) The raw materials mainly including the following components are mixed by mass fraction to prepare the mixture:

[0096] Polyvinyl alcohol fiber 4 parts,

[0097] Polyvinyl alcohol solution 1000 parts,

[0098] Nano ZnO dispersion liquid 100 parts;

[0099] The mass concentration of the polyvinyl alcohol solution is 5wt%,

[0100] The mass concentration of the nano ZnO dispersion liquid is 30wt%;

[0101] (2) The mixture prepared in step (1) is placed under ultrasonic conditions for 4-6 hours, and then the treated polyvinyl alcohol fibers are filtered out, washed with deionized water, and dried at 50°C to be used;

[0102] (3) The treated polyvinyl alcohol fibers obtained in step (2) are mixed with epoxy resin and other conventional additives by a vacuum assisted resin transfer molding (VARTM) process to prepare PVA fiber / nano-ZnO / epoxy resin composites. The vacuum assisted resin transfer molding (VARTM) process is as follows: a flow guide net, a release cloth, the treated polyvinyl alcohol fibers, a release cloth, and a flow guide net are sequentially placed on a hot table, glue injection seats are placed at both ends of the hot table, a spiral pipe is laid between the glue injection seats and the polyvinyl alcohol fibers and around the materials, and the materials placed on the hot table are sealed; holes are drilled in the glue injection seats at both ends to connect hoses, one end of the hose flows into a mixture of epoxy resin and other conventional additives, and the other end of the hose is connected to a vacuum pump and a surplus resin collector; wherein the process conditions of the vacuum assisted resin transfer molding (VARTM) process are as follows: the temperature is set at 100°C, and the vacuum degree is maintained at 0.08 MPa for 6 hours.

[0103] The other conventional additives include 10wt% ethylene glycol diglycidyl ether, 25wt% 4,4-diaminodiphenyl methane, and 0.05wt% 2-ethyl-4-methylimidazole, based on the mass percentage of epoxy resin.

[0104] 3. Test method

[0105] Interlaminar shear property test

[0106] According to GB / T 6344-2008 / ISO 1798-2008, the interlaminar shear property is determined by an Instron 5567 electronic universal material testing machine of Instron Company, USA. The experimental speed is 5 mm / min.

[0107] Scanning electron microscope test (SEM)

[0108] The fiber surface morphology is observed by a JSM-5900LV scanning electron microscope of JEOL Company, Japan.

[0109] Atomic force microscope test (AFM)

[0110] The fiber surface morphology and surface roughness are analyzed by a Smart SPM atomic force microscope of AIST-NT Company, USA.

[0111] Example 1

[0112] Example 1 PVA fiber@nano-ZnO / epoxy resin composite material was prepared according to the steps described in the above "2. Preparation method", as the sample of Example 1.

[0113] Comparative Example 1

[0114] Comparative Example 1 was prepared according to the steps described in the above "2. Preparation method", but without adding polyvinyl alcohol solution and nano-ZnO dispersion, to prepare PVA fiber reinforced epoxy resin composite material, as the sample of Comparative Example 1.

[0115] Comparative Example 2

[0116] Comparative Example 2 was prepared according to the steps described in the above "2. Preparation method", but the polyvinyl alcohol solution was replaced by the same mass fraction of deionized water, to prepare PVA fiber@nano-ZnO / epoxy resin composite material, as the sample of Comparative Example 2.

[0117] The samples prepared in Example 1, Comparative Examples 1-2 were subjected to interlaminar shear property test, and the test results are shown in Table 1 below:

[0118] Table 1 Performance test results of samples of Example 1, Comparative Examples 1-2

[0119] Example 1 Comparative Example 1 Comparative Example 2 Interlaminar shear strength / MPa 122.3 99.4 105.8

[0120] From Table 1, it can be seen that the PVA fiber reinforced epoxy resin composite material prepared by the PVA fiber modified by solution method in Example 1, Comparative Examples 1-2 has better mechanical properties than the same kind of product on the market. However, without the addition of nano-ZnO dispersion (Comparative Example 1), the interlaminar shear strength is still less than 100 MPa, and with the addition of nano-ZnO dispersion (Comparative Example 2), we found that the strength of the sample increased significantly, but the growth was very limited.

[0121] The present application explores the synergistic effect between PVA fiber, PVA solution and nano-ZnO dispersion, which significantly further improves the strength of the prepared PVA fiber@nano-ZnO / epoxy resin composite material. In addition, the energy consumption and cost required by the embodiments of the present application are low, and are easier to realize than the commonly used electrodeposition method and hydrothermal method.

[0122] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A method for preparing a PVA fiber@nano-ZnO / epoxy resin composite material, characterized in that... The method comprises the following steps: (1) mixing raw materials including the following components by mass fraction to prepare materials, as a mixture: Polyvinyl alcohol fiber 2~4 parts, Polyvinyl alcohol solution 1000 ~1200 parts, Nano ZnO dispersion liquid 100~150 parts; The mass concentration of the polyvinyl alcohol solution is 5~10wt%, The mass concentration of the nano ZnO dispersion liquid is 30~40wt%; (2) placing the mixture prepared in step (1) under stirring or ultrasonic conditions for 4~6h, then filtering out the treated polyvinyl alcohol fiber, washing and drying for standby; (3) mixing the treated polyvinyl alcohol fiber obtained in step (2) with epoxy resin and other conventional additives by vacuum assisted resin transfer molding process to prepare PVA fiber@ nano ZnO / epoxy resin composite; wherein the process conditions of the vacuum assisted resin transfer molding process are: setting the temperature at 60~160℃, maintaining the vacuum degree at 0.06~0.1MPa for 4~8h.

2. The method of claim 1, wherein: The polyvinyl alcohol fiber in step (1) is selected from polyvinyl alcohol fibers having a density of 1.1 to 1.3 g / cm 3 , a 5 to 10 times elongation ratio, an orientation degree of 94 to 98%, and a tensile strength of 285 to 500 MPa.

3. The method of claim 1, wherein: The pretreatment of polyvinyl alcohol fiber in step (1) is to clean the polyvinyl alcohol fiber with organic reagent and dry at 50℃ for 2~4h.

4. The method of claim 1, wherein: The polyvinyl alcohol solution in step (1) is polyvinyl alcohol aqueous solution.

5. The method of claim 1, wherein: The solvent of the nano ZnO dispersion liquid in step (1) is selected from any one of 1,2-propanediol monomethyl ether acetate, isooctyl ester, Tween 60, Span 80.

6. The method of claim 1, wherein: In step (3), the vacuum assisted resin transfer molding process is as follows: placing the flow guide net, release cloth, treated polyvinyl alcohol fiber, release cloth and flow guide net as materials on the hot table, placing the glue injection seat at both ends of the hot table, laying the spiral pipe between the glue injection seat and the polyvinyl alcohol fiber and around the materials, then sealing the materials placed above the hot table; drilling holes on the glue injection seats at both ends to connect the hoses, one end of the hose flows into the mixture of epoxy resin and other conventional additives, and the other end of the hose is connected with the vacuum pump and the excess resin collector.

7. The method of claim 1, wherein: The epoxy resin in step (3) is selected from bisphenol A type epoxy resin or phenolic type epoxy resin.

8. The method of claim 1, wherein: The other conventional additives in step (3) include diluents, curing agents, crosslinking catalysts.

9. A method for preparing the PVA fiber@ nano ZnO / epoxy resin composite material of claim 1.

10. The application of the PVA fiber@ nano ZnO / epoxy resin composite material of claim 9 as a structural material.

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