Reaction-type deep eutectic solvent flame-retardant modified plant fiber composite material and preparation method thereof

Abstract

The application discloses a kind of reactive low consolute solvent flame-retardant modified plant fiber composites and preparation method thereof, belong to natural polymer material technical field.The application is with plant fiber as raw material, after being modified by reactive low consolute solvent, flame-retardant plant fiber is prepared, flame-retardant plant fiber is mixed with water-based epoxy resin, curing agent, water, after hot-pressing, curing, the reactive low consolute solvent flame-retardant modified plant fiber composite material with limiting oxygen index not less than 35% is prepared.The application utilizes the surface active hydroxyl group of plant fiber and the DES reaction of flame-retardant element such as phosphorus, nitrogen and sulfur, realizes that plant fiber surface is in situ grafted flame-retardant modification;Covalent bond is generated between the flame-retardant group phosphonic group, amine group on the surface of DES modified plant fiber and the epoxy group of matrix epoxy resin, realizes the interface enhancement of composite material fiber reinforced phase and resin matrix phase;Plant fiber composite material is prepared, which has excellent flame-retardant performance and better mechanical property.

Description

Technical Field

[0001] This invention belongs to the field of natural polymer materials technology, and more specifically, relates to a reactive eutectic solvent flame-retardant modified plant fiber composite material and its preparation method. Background Technology

[0002] Compared to traditional composite materials, plant fiber composites possess advantages such as biodegradability, light weight, and high rigidity, and have been applied in fields such as construction, packaging, sheet materials, 3D printing, and automobiles, representing a future trend in composite material development. However, compared to glass fiber, plant fibers and their reinforced composites are flammable, significantly limiting the application areas and scope of these products.

[0003] Flame retardancy has always been a major challenge hindering the development of plant fiber composites. Currently, the most common flame retardant strategy is to directly add flame retardants to plant fiber composites to improve their flame retardant properties. Existing research shows that while adding flame retardants can improve the flame retardant properties of plant fiber composites, the required dosage is usually large. This not only reduces the amount of plant fiber in the composite but also leads to a decrease in the mechanical properties of the composite due to the poor interfacial properties between the plant fiber, matrix resin, and flame retardant. Achieving synergistic flame retardancy and reinforcement in plant fiber composites is a pressing scientific challenge that needs to be addressed in this field.

[0004] Eutectic solvents (DES) are a class of self-associated liquid mixtures, typically composed of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs). DES contain numerous intramolecular hydrogen bonds, which can promote the breaking of strong hydrogen bonds between biomass molecules, thus exhibiting high biomass solubility and excellent modification effects, making them highly promising for biomass refining, pretreatment, and modification. Furthermore, DES is characterized by low cost, environmental friendliness, and reusability, making it a currently popular green modification method for plant fibers. DES can be classified into reactive and non-reactive systems based on whether they react with the substrate. In recent years, researchers have explored using DES that can react with cellulose hydroxyl groups to treat plant fibers, derivatizing the cellulose hydroxyl groups and thus endowing the materials with more functional properties. Introducing flame-retardant elements such as sulfur and nitrogen into the cellulose molecular structure using reactive DES can impart flame-retardant properties to cellulose materials without affecting their mechanical properties. The greatest advantage of DES lies in its designability. By utilizing the flexible selection and free control between hydrogen bond donors and acceptors, multi-component DES containing flame-retardant elements can be prepared. More flame-retardant elements such as phosphorus, nitrogen, sulfur, and silicon can be introduced into the molecular structure of cellulose, giving full play to the synergistic flame-retardant effect between different flame-retardant elements, and realizing green and efficient flame-retardant modification of plant fibers. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the technical problem to be solved by this invention is to provide a method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material. This method utilizes the covalent bonding between the flame-retardant phosphate and amine groups on the surface of the DES-modified plant fibers and the epoxy groups of the matrix epoxy resin, thereby achieving interfacial reinforcement between the fiber reinforcement phase and the resin matrix phase of the composite material. Another technical problem to be solved by this invention is to provide a reactive eutectic solvent flame-retardant modified plant fiber composite material prepared by the above method, which exhibits both excellent flame-retardant properties and good mechanical properties.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material involves using plant fiber as raw material, modifying it with a reactive eutectic solvent to obtain flame-retardant plant fiber, mixing the flame-retardant plant fiber with waterborne epoxy resin, curing agent, and water, and then hot-pressing and curing the mixture to obtain a reactive eutectic solvent flame-retardant modified plant fiber composite material with a limiting oxygen index of not less than 35%.

[0008] Preferably, the reactive eutectic solvent consists of a proton donor and a proton acceptor that can react with cellulose hydroxyl groups.

[0009] Preferably, the proton donor is selected from any one or more of phosphoric acid, phytic acid, aminosulfonic acid, urea, and amino acids.

[0010] Preferably, the proton acceptor is selected from any one or more of betaine, betaine hydrochloride, and choline chloride.

[0011] Preferably, the plant fiber is selected from any one or more of wood fiber, cotton fiber, hemp fiber, and bamboo fiber.

[0012] Preferably, the curing agent is selected from any one or more of polyetheramine, polyamide, aliphatic amine, cycloaliphatic amine, and aromatic amine.

[0013] Preferably, the temperature of the modification treatment is 80~150℃ and the treatment time is 0.5~5h.

[0014] Preferably, the hot pressing temperature is 160°C and the hot pressing time is 50~55 min.

[0015] Preferably, the mass ratio of the flame-retardant plant fiber, waterborne epoxy resin, curing agent and water is 96:40:4:100.

[0016] The reactive eutectic solvent flame-retardant modified plant fiber composite material prepared by the aforementioned method is a reactive eutectic solvent flame-retardant modified plant fiber composite material.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1) This invention utilizes in-situ grafting of phosphorus-nitrogen-containing reactive DES onto the surface of plant fibers with hydroxyl groups to achieve uniform dispersion of flame retardant elements on the fiber surface, thus solving the problem of uniform dispersion of flame retardants in composite materials.

[0019] 2) This invention utilizes the covalent bonding between the surface active groups (flame retardant groups, phosphate groups, and amine groups) of DES-modified plant fibers and the epoxy groups of waterborne epoxy resin to achieve interfacial chemical coupling, thereby solving the interfacial compatibility problem between flame retardants, plant fibers, and matrix resins. The prepared plant fiber composite material has both excellent flame retardant properties and good mechanical properties, achieving a synergistic effect of flame retardancy and high strength in plant fiber composite materials. Attached Figure Description

[0020] Figure 1 X-ray photoelectron spectra of wood fibers before and after reactive DES modification in Example 1;

[0021] Figure 2 This is a scanning electron microscope image of wood fibers modified with reactive DES in Example 2.

[0022] Figure 3 The p-element energy spectrum of wood fibers modified with reactive DES in Example 3 is shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0024] The wood fiber used in the following examples is fir fiber, produced by the Pulping and Paper R&D Center of the Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry, using a high-yield pulping process, with an average length of 2.3 mm and a width of 45 μm. The hemp fiber is ramie fiber, provided by Chenzhou Xiangnan Hemp Industry Co., Ltd., with an average single fiber length of 11.7 mm and an average fineness of 6.10 dtex. The cotton fiber is long-staple cotton, provided by Mengcun Hui Autonomous County Qiancengxue Cotton Factory, with a fiber length of 34.37 mm and a fineness of 7080 m / g. The bamboo fiber is bamboo virgin fiber, provided by Sichuan Changsheng New Material Technology Co., Ltd., with an average fiber length of 14.6 mm and an average fineness of 5.50 dtex.

[0025] The waterborne epoxy resin WER5625 was provided by Jiangsu Ruiyang Antai New Material Technology Co., Ltd., with a solid content of 50% and an epoxy value of 0.20 mol / 100g. The polyamide curing agent, 5115x70 polyamide curing agent with an amine value of 145-175 mgKOH / g, was provided by Suzhou Hengsite Industrial Co., Ltd.

[0026] The aromatic amine curing agent is diaminodiphenylmethane or diethyltoluenediamine; wherein, the amine value of diaminodiphenylmethane is 566 mg / g, and the amine value of diethyltoluenediamine is 629 mg / g.

[0027] Example 1

[0028] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0029] 1) Mix phosphoric acid, urea and choline chloride in a molar ratio of 1:2:1, heat and stir in an oil bath at 90°C for 60 minutes until the solution is clear to obtain reactive DES;

[0030] 2) Add wood fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the wood fiber dry and dry it in an oven at 100℃ for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80℃ for 4 h to obtain reactive DES modified wood fiber.

[0031] 3) Put 96 g of reactive DES modified wood fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diaminodiphenylmethane and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0032] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0033] Example 2

[0034] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0035] 1) Mix phytic acid, urea and betaine in a molar ratio of 1:2:1, heat and stir in an oil bath at 90°C for 60 minutes until the solution is clear to obtain reactive DES;

[0036] 2) Add wood fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the wood fiber dry and dry it in an oven at 100℃ for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80℃ for 4 h to obtain reactive DES modified wood fiber.

[0037] 3) Put 96 g of the reactive DES modified wood fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diethyltoluene diamine and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0038] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0039] Example 3

[0040] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0041] 1) Phosphoric acid, urea and glycine were mixed in a molar ratio of 1:2:1 and heated and stirred in an oil bath at 90°C for 60 minutes until the solution was clear to obtain reactive DES;

[0042] 2) Add wood fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the wood fiber dry and dry it in an oven at 120°C for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80°C for 4 h to obtain reactive DES modified wood fiber.

[0043] 3) Put 96 g of the reactive DES modified wood fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diethyltoluene diamine and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0044] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0045] Example 4

[0046] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0047] 1) Phosphoric acid, urea and glycine were mixed in a molar ratio of 1:2:1 and heated and stirred in an oil bath at 90°C for 60 minutes until the solution was clear to obtain reactive DES;

[0048] 2) Add hemp fibers to the reactive DES prepared in step 1) and soak for 10 minutes. Then squeeze the hemp fibers dry and dry them in an oven at 120°C for 4 hours. After washing the dried fibers until neutral, continue to dry them in an oven at 80°C for 4 hours to obtain reactive DES modified hemp fibers.

[0049] 3) Put 96 g of the reactive DES modified hemp fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diethyltoluene diamine and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0050] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified hemp fiber / waterborne epoxy resin composite material.

[0051] Example 5

[0052] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0053] 1) Mix phosphoric acid, urea and aminosulfonic acid in a molar ratio of 1:2:1, heat and stir in an oil bath at 90°C for 60 min until the solution is clear to obtain reactive DES;

[0054] 2) Soak cotton fibers in the reactive DES prepared in step 1) for 10 minutes, then squeeze the cotton fibers dry and dry them in an oven at 120°C for 4 hours. After washing the dried fibers until neutral, continue to dry them in an oven at 80°C for 4 hours to obtain reactive DES modified cotton fibers.

[0055] 3) Put 96 g of the reactive DES modified cotton fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of polyamide curing agent and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0056] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified cotton fiber / waterborne epoxy resin composite material.

[0057] Example 6

[0058] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0059] 1) Phytic acid, urea and betaine hydrochloride were mixed in a molar ratio of 1:2:1 and heated and stirred in an oil bath at 90°C for 60 minutes until the solution was clear to obtain reactive DES.

[0060] 2) Add bamboo fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the cotton fiber dry and dry it in an oven at 100℃ for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80℃ for 4 h to obtain reactive DES modified bamboo fiber.

[0061] 3) Put 96 g of reactive DES modified bamboo fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diaminodiphenylmethane and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0062] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified bamboo fiber / waterborne epoxy resin composite material.

[0063] Example 7

[0064] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0065] 1) Mix phosphoric acid, urea and choline chloride in a molar ratio of 2:2:1, heat and stir in an oil bath at 90°C for 60 minutes until the solution is clear to obtain reactive DES;

[0066] 2) Add wood fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the wood fiber dry and dry it in an oven at 100℃ for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80℃ for 4 h to obtain reactive DES modified wood fiber.

[0067] 3) Put 96 g of reactive DES modified wood fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diaminodiphenylmethane and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0068] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0069] Example 8

[0070] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0071] 1) Mix phosphoric acid, urea and choline chloride in a molar ratio of 1:2:1, heat and stir in an oil bath at 90°C for 60 minutes until the solution is clear to obtain reactive DES;

[0072] 2) Add wood fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the wood fiber dry and dry it in an oven at 100℃ for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80℃ for 4 h to obtain reactive DES modified wood fiber.

[0073] 3) Put 96 g of reactive DES modified wood fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diaminodiphenylmethane and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0074] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0075] Example 9

[0076] A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material includes the following steps:

[0077] 1) Mix phosphoric acid, urea and choline chloride in a molar ratio of 1:2:1, heat and stir in an oil bath at 90°C for 60 minutes until the solution is clear to obtain reactive DES;

[0078] 2) Add wood fiber to the reactive DES prepared in step 1) and soak for 10 min. Then squeeze the wood fiber dry and dry it in an oven at 100℃ for 4 h. Then wash the dried fiber until neutral and continue to dry it in an oven at 80℃ for 4 h to obtain reactive DES modified wood fiber.

[0079] 3) Put 96 g of the reactive DES modified wood fiber obtained in step 2), 40 g of waterborne epoxy resin WER5625, 4 g of diethyltoluene diamine and 100 g of water into a kneader and knead for 30 min to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 h. After drying the moisture, the prepreg is obtained.

[0080] 4) The prepreg obtained in step 3) is evenly spread into the mold, placed in a 120℃ hot press for 5 minutes, and then hot-pressed for 50 minutes to obtain the sample. After demolding, the sample is placed in a 120℃ oven and cured for 5 hours to obtain the reactive DES flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0081] Comparative Example 1

[0082] A method for preparing an unflame-retardant modified wood fiber / waterborne epoxy resin composite material includes the following steps:

[0083] 1) Put 96g of wood fiber, 40g of waterborne epoxy resin WER5625, 4g of diethyltoluene diamine and 100g of water into a kneader and knead for 30 minutes to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 hours. After drying the moisture, the prepreg is obtained.

[0084] 2) Spread the prepreg evenly into the mold, place it in a 160℃ hot press for 5 minutes, and then hot press for 45~50 minutes to obtain the sample. After demolding, place the sample in a 150℃ oven and cure for 5 hours to obtain the wood fiber / waterborne epoxy resin composite material.

[0085] Comparative Example 2

[0086] The traditional method for preparing wood fiber / waterborne epoxy resin composites modified with ammonium polyphosphate flame retardant includes the following steps:

[0087] 1) Dissolve 96g of wood fiber, 40g of waterborne epoxy resin WER5625, 4g of diethyltoluene diamine and 20g of water-soluble ammonium polyphosphate in 100g of water, put them in a kneader and knead for 30min to mix thoroughly. Take out the mixture and put it in a 60℃ oven to dry for 2h. After drying the moisture, the prepreg is obtained.

[0088] 2) The prepreg is evenly spread into the mold, placed in a 160℃ hot press for 5 minutes, and then hot-pressed for 45~50 minutes to obtain the sample. After demolding, the sample is placed in a 150℃ oven and cured for 5 hours to obtain the ammonium polyphosphate flame-retardant modified wood fiber / waterborne epoxy resin composite material.

[0089] Comparative Example 3

[0090] A method for preparing a hemp fiber / waterborne epoxy resin composite material includes the following steps:

[0091] 1) Put 96g of hemp fiber, 40g of waterborne epoxy resin WER5625, 4g of diethyltoluene diamine and 100g of water into a kneader and knead for 30 minutes to mix thoroughly. Take out the mixture and put it into a 60℃ oven to dry for 2 hours. After drying the moisture, the prepreg is obtained.

[0092] 2) Spread the prepreg evenly into the mold, place it in a 160℃ hot press for 5 minutes, and then hot press for 45~50 minutes to obtain the sample. After demolding, place the sample in a 150℃ oven and cure for 5 hours to obtain the wood fiber / waterborne epoxy resin composite material.

[0093] The composite materials prepared in Examples 1-9 and Comparative Examples 1-3 were subjected to performance tests. Bending and tensile properties were measured using a universal testing machine equipped with a 30 kN load sensor. According to GT / B1449-2005 standard, the composite materials with dimensions of 120 × 15 × 3.5 mm were tested at a speed of 2 mm / min and a span of 64 mm. 3 The bending sample was tested. According to GT / B1040.2-2022 standard, the tensile sample (80×10×3.5 mm) was tested at a speed of 2 mm / min. 3 The test was conducted using a limiting oxygen index meter (JF-5 oxygen index meter) with a narrow section width of 5 mm. The limiting oxygen index of the samples was determined according to the national standard GB / T5454-1997. The results are shown in Table 1.

[0094] Table 1. Performance test results of the composite materials prepared in Examples 1-9 and Comparative Examples 1-3.

[0095]

[0096] Table 1 shows that traditional addition of ammonium polyphosphate flame retardant can improve the limiting oxygen index (flame retardancy) of wood fiber / waterborne epoxy resin composites, but its flexural strength decreases significantly. Reactive DES flame retardant modification can achieve a limiting oxygen index of 50% for wood fiber / waterborne epoxy resin composites, but the flexural strength does not decrease significantly. Excessive curing agent dosage will reduce the mechanical properties of the composite. Lowering the hot-pressing temperature, resulting in incomplete curing, will also reduce the mechanical properties of the composite.

[0097] Depend on Figure 1 It can be seen that the characteristic peaks of flame retardant elements P and N appeared in the spectrum after DES modification, and the characteristic peaks of P and N were significantly enhanced with the increase of reaction temperature, indicating that reactive DES has been successfully grafted onto the surface of wood fiber structure.

[0098] Depend on Figure 2 It can be seen that the wood fibers still maintain a rod-like structure after DES modification.

[0099] Depend on Figure 3 It can be seen that the flame retardant element P is evenly distributed on the surface of the wood fiber, indicating that the flame retardant is evenly distributed in the fiber structure, overcoming the shortcomings of ordinary additive flame retardants that are not easy to disperse and are easy to agglomerate.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a reactive eutectic solvent flame-retardant modified plant fiber composite material, characterized in that, Flame-retardant plant fibers are prepared by modifying plant fibers with a reactive eutectic solvent. The flame-retardant plant fibers are then mixed with water-based epoxy resin, curing agent, and water, and hot-pressed and cured to obtain a reactive eutectic solvent-modified plant fiber composite material with a limiting oxygen index of not less than 35%. The reactive eutectic solvent is composed of a proton donor and a proton acceptor that can react with cellulose hydroxyl groups. The proton donor is phosphoric acid and urea, or phytic acid and urea. The proton acceptor is selected from any one or more of betaine, betaine hydrochloride, and choline chloride.

2. The preparation method of the reactive eutectic solvent flame-retardant modified plant fiber composite material according to claim 1, characterized in that, The plant fiber is selected from any one or more of wood fiber, cotton fiber, hemp fiber, and bamboo fiber.

3. The preparation method of the reactive eutectic solvent flame-retardant modified plant fiber composite material according to claim 1, characterized in that, The curing agent is selected from any one or more of polyetheramine, polyamide, aliphatic amine, cycloaliphatic amine, and aromatic amine.

4. The preparation method of the reactive eutectic solvent flame-retardant modified plant fiber composite material according to claim 1, characterized in that, The modification treatment is performed at a temperature of 80~150℃ for a duration of 0.5~5h.

5. The method for preparing the reactive eutectic solvent flame-retardant modified plant fiber composite material according to claim 1, characterized in that, The hot pressing temperature is 160℃, and the hot pressing time is 50~55min.

6. The preparation method of the reactive eutectic solvent flame-retardant modified plant fiber composite material according to claim 1, characterized in that, The mass ratio of the flame-retardant plant fiber, water-based epoxy resin, curing agent and water is 96:40:4:

100.

7. The reactive eutectic solvent flame-retardant modified plant fiber composite material prepared by the method according to any one of claims 1-6.

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