Epoxy resin flame retardant based on one-dimensional-two-dimensional layered structure nano hybrid as well as preparation method and application of epoxy resin flame retardant

Abstract

The invention discloses an epoxy resin flame retardant based on a one-dimensional-two-dimensional layered structure nano hybrid as well as a preparation method and application of the epoxy resin flame retardant. According to the flame retardant, graphene oxide (GO) is used as a matrix, GO-APTES with larger interlayer spacing is obtained by modifying GO through APTES, and nanosheets are more dispersed. Then, dopamine is oxidized and self-polymerized under the alkaline condition to form a PDA coating, the surface of the beta-FeOOH nanorod is uniformly coated with the PDA coating, and beta-FeOOH is densely and stably loaded on GO-APTES nanosheets through the interaction of rich catechol / amine groups of the PDA coating and strong hydrogen bonds on the surface of GO-APTES, so that a GA (at) PDA (at) beta-FeOOH nanohybrid is prepared; the obtained GA (at) PDA (at) beta-FeOOH nano hybrid has good dispersibility in an epoxy resin matrix. When the flame retardant is applied to epoxy resin, the thermal stability and flame retardance of a composite material can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of epoxy resin flame-retardant flame retardants, and particularly relates to an epoxy resin flame retardant based on one-dimensional-two-dimensional layered structure nanohybrid GA@PDA@beta-FeOOH and a preparation method and application thereof. BACKGROUND

[0002] Epoxy resin (EP) is one of the typical thermosetting resins, which has excellent physical and mechanical, chemical stability and electrical insulation performance, making EP widely used in construction, automobile, electronics and aerospace fields, and has become an indispensable basic material in high-end manufacturing industries such as 5G communication and rail transportation. However, high flammability is one of the main problems that cannot be ignored for epoxy resin, which limits the application of EP. In addition, the combustion of EP always produces a large amount of heat, smoke particles and harmful and toxic gases (HCN, CO), which endanger the environment and human health, so the development of EP flame retardants with flame retardant performance has become a research hotspot. This new material will help to manufacture safer and more environmentally friendly EP products.

[0003] At present, the traditional halogen-free flame retardant materials mainly include metal hydroxides, nitrogen-containing compounds and phosphorus-containing compounds. However, metal hydroxides need a high addition amount (≥50 wt%), which seriously damages the mechanical and processing properties of the composite materials; although phosphorus-based and phosphorus-nitrogen-based flame retardants are relatively efficient and low-toxic, they still face problems such as poor thermal stability, easy migration and poor compatibility with the matrix, which often leads to a decrease in the mechanical properties of the materials. Therefore, it is still a great challenge to design environmentally friendly and efficient flame retardant materials to manufacture polymer materials with high flame retardancy and mechanical properties.

[0004] The emergence of nanometer flame retardants can significantly improve the flame retardancy of polymers at a very low addition amount, and their small size and ultra-high specific surface area help to achieve good dispersion in epoxy resin (EP) and enhance the flame retardant effect. Representative nanometer materials include carbon dots, carbon nanotubes, graphene and graphene oxide (GO). Among them, GO has great potential in flame retardant applications due to its high specific surface area, rich surface functional groups and easy processability. However, GO is prone to aggregation, and it is easy to curl during combustion, which affects the play of its barrier performance, so surface modification of GO is the key to breaking this bottleneck, and the dispersion, interfacial compatibility and flame retardant synergistic effect need to be improved through surface modification.

[0005] (3-aminopropyl)triethoxysilane (APTES) is often used to modify GO to increase the interlayer spacing, and the tail end amino group can improve the compatibility with the EP matrix; polydopamine (PDA) has good adhesion to inorganic components during in-situ polymerization, which ensures the uniform distribution of nanohybrid and stronger interaction between components.

[0006] Therefore, it is urgent to develop a new flame-retardant strategy to achieve the balance between the flame retardancy and mechanical properties of epoxy resin at a low additive amount by using one-dimensional-two-dimensional layered structure nanohybrids prepared on a large scale, which integrate the flame-retardant functions of β-FeOOH (radical scavenging and catalytic carbon layer formation) and GO (barrier effect). SUMMARY

[0007] The technical problem to be solved by the present application is to provide a GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid and an epoxy resin flame retardant based on the one-dimensional-two-dimensional layered structure nanohybrid GA@PDA@β-FeOOH, which has good compatibility with epoxy resin and excellent flame-retardant effect in application.

[0008] The technical scheme adopted by the present application to solve the above-mentioned problems is: The preparation method of the GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid comprises the following steps: (1) Synthesis of GO: slowly pour a sulfuric acid and phosphoric acid mixture into a reactor containing graphite powder and stir uniformly; slowly add potassium permanganate powder, and keep the temperature of the mixture below 50°C during this process; then stir at 50-60°C for 5-7 hours, add a diluted hydrogen peroxide solution until no bubbles are generated; continue stirring at 50-60°C for 1-3 hours, cool to room temperature, centrifuge the suspension at a speed of 9000-11000 rpm for 4-6 minutes, wash with deionized water for 6-8 times, and freeze-dry for 1-3 days to obtain GO nanosheets; (2) Synthesis of β-FeOOH: prepare a 0.1-0.4 M aqueous solution of FeCl3·6H2O, and place it in a reaction kettle for hydrothermal reaction at 115-125°C for 10-14 hours; centrifuge after cooling to room temperature, wash with deionized water for 3 times, and dry to obtain β-FeOOH nanorods; (3) Preparation of GO-APTES: mix the GO nanosheets obtained in step (1) with a toluene solution; quickly add an APTES solution and mix uniformly; stir at 60-80°C for 10-14 hours in a nitrogen atmosphere; centrifuge after cooling to room temperature, wash with anhydrous ethanol for 3 times, and dry to obtain GO-APTES powder, which is abbreviated as GA; (4) Preparation of PDA@β-FeOOH: disperse the β-FeOOH nanorods obtained in step (2) in a Tris-HCl buffer solution (concentration 5-15 mM), add dopamine hydrochloride, and stir at room temperature for 10-14 hours; centrifuge after the reaction is completed, wash with deionized water for 3 times, and dry to obtain PDA@β-FeOOH powder; (5) Preparation of GA@PDA@β-FeOOH: The GO-APTES powder obtained in step (3) is prepared into an aqueous solution, and the PDA@β-FeOOH powder obtained in step (4) is added into the solution and stirred at room temperature for 22-26 hours. After centrifugation and drying, the GA@PDA@β-FeOOH powder is obtained, wherein GA is a shorthand for the GO-APTES powder, and the shorthand is used hereinafter.

[0009] Preferably, in step (1), the concentration of the hydrogen peroxide solution is 4%-6%.

[0010] Preferably, in step (3), the mass-volume ratio of the GO nanosheet to the toluene solution is 1:5-7 g / mL.

[0011] Preferably, in step (4), the mass ratio of the β-FeOOH nanorod to the dopamine hydrochloride is 1:0.1-0.5.

[0012] Preferably, in step (5), the mass ratio of the GO-APTES powder to the PDA@β-FeOOH powder is 1:5-10.

[0013] Further preferably, in step (1), the centrifugal speed is 10000 rpm.

[0014] Further preferably, in step (3), the amount of APTES added is 6 mL.

[0015] Further preferably, in step (4), the concentration of the Tris-HCl buffer is 10 mM, and the amount of dopamine hydrochloride added is 0.2 g.

[0016] Further preferably, in step (5), the amount of PDA@β-FeOOH powder added is 5 g.

[0017] An epoxy resin flame retardant based on a GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid is an epoxy resin / GA@PDA@β-FeOOH composite material obtained by compounding a GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid with an epoxy resin. The preparation method comprises the following steps: (a) dispersing the GA@PDA@β-FeOOH powder obtained by the above method in acetone and ultrasonic treatment for 0.4-0.6 hours; (b) adding the dispersion liquid into the epoxy resin preheated at 110-120°C and stirring for 1-2 hours; (c) adding 20%-30% of diamino diphenyl methane (DDM) by mass of the epoxy resin, uniformly mixing, and then pouring into a mold; (d) ladder curing: curing at 100-110 DEG C for 1.5-2.5 hours, and then curing at 150-160 DEG C for 1.5-2.5 hours, to obtain the epoxy resin / GA@PDA@beta-FeOOH composite material.

[0018] Preferably, the added amount of the GA@PDA@beta-FeOOH is 1-10 wt% of the mass of the epoxy resin.

[0019] The one-dimensional-two-dimensional layered structure nanohybrid GA@PDA@beta-FeOOH obtained by the above method is a new one-dimensional-two-dimensional hybrid layered structure synthesized by double modification of two-dimensional GO by one-dimensional beta-FeOOH nanorods coated with (3-aminopropyl) triethoxysilane (APTES) and polydopamine (PDA) to improve the compatibility with the polymer matrix; the structure increases the interlayer spacing of GO by APTES, facilitates subsequent synthesis, and the terminal amino group can enhance its dispersion in the polymer matrix, and the strong adhesion and high reactivity of the PDA layer realize the close connection of GO and beta-FeOOH to ensure uniform loading and form a stable structure.

[0020] The epoxy resin / GA@PDA@beta-FeOOH composite material obtained by the above method, the epoxy resin is a continuous phase, wherein the GA@PDA@beta-FeOOH nanohybrid is uniformly dispersed and firmly combined by chemical bonding; the nanohybrid is composed of beta-FeOOH nanorods coated with PDA densely anchored on APTES modified GO nanosheets, and its unique hierarchical structure not only endows the particles with high stability and high surface reactivity, but also realizes efficient stress transfer in the composite material and significantly reduces the reduction of the mechanical strength and modulus of the epoxy resin caused by the agglomeration of GO.

[0021] The GA@PDA@beta-FeOOH one-dimensional-two-dimensional layered nanohybrid and the epoxy resin / GA@PDA@beta-FeOOH composite material prepared by the present application can be applied to the fields of coatings, adhesives, electronic device packaging agents and soil building industries.

[0022] The prepared flame retardant takes the APTES modified GO nanosheet as a matrix, and since PDA has good adhesion to inorganic components during in-situ polymerization, the beta-FeOOH nanorod is better fixed on the GO surface through PDA coating. Specifically, dopamine is used to form a PDA coating layer through oxidation and self-polymerization under alkaline conditions, and the coating is realized through the coordination of the rich catechol / amine groups of PDA with the iron ions in the beta-FeOOH nanorod; then, the beta-FeOOH coated with PDA is loaded on the GO layer covalently modified by APTES, so as to ensure the uniform distribution of the nanosheet and the stronger interaction between the components, and a one-dimensional-two-dimensional layered structure is constructed. The obtained GA@PDA@beta-FeOOH nanohybrid has good dispersibility in an epoxy resin matrix. When the flame retardant is applied to the epoxy resin, the thermal stability and the flame retardant performance of the composite material can be significantly improved, for example, the total smoke production (TSP) can be greatly reduced (the reduction can reach 65.3%). The flame retardant mechanism is mainly attributed to the synergistic effect of GO and beta-FeOOH, including barrier effect, catalytic carbon formation and gas phase free radical quenching effect. The flame retardant provided by the application has the advantages of low addition amount, high flame retardant efficiency, little influence on the mechanical properties of the matrix and the like.

[0023] Compared with the prior art, the application has the following beneficial effects: The application constructs a one-dimensional-two-dimensional layered structure flame retardant by taking polydopamine (PDA) as a good organic bridge, densely loading beta-FeOOH on the APTES modified GO nanosheet through PDA. The loading of beta-FeOOH nanorods on the GO nanosheet can prevent curling, enhance the barrier effect of GO, and connect the dispersed beta-FeOOH nanorods to reduce the generation of holes or cracks, so that the carbon layer is more dense. The modified filler obtains the synergistic effect of beta-FeOOH (free radical scavenging and catalytic carbon layer formation) and GO (barrier effect), and forms a more effective flame retardant mechanism. The obtained flame retardant can make the UL-94 rating of the epoxy resin composite material reach V-0 level when the addition amount is 7 wt%, the LOI value is increased to 30.13%, and the mechanical properties of the composite material are basically the same as those of the pure EP material due to the prevention of GO agglomeration by beta-FeOOH and the improvement of the dispersibility of GO in the matrix; the technical problem of damage to the mechanical properties and process adaptability caused by high addition amount (more than 20 wt%) of traditional flame retardants is solved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1(a), (b), (c), (d), (e), and (f) are scanning electron microscope images of β-FeOOH nanorods prepared in Example 1, PDA@β-FeOOH powder and its partial magnified image, GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered nanohybrid images, respectively.

[0025] Figure 2 The infrared spectra are those of the GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered nanohybrids prepared in Example 1.

[0026] Figure 3 The figures show the thermal decomposition curves of the β-FeOOH nanorods, PDA@β-FeOOH powder, GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional to two-dimensional layered nanohybrids prepared in Example 1 under nitrogen conditions.

[0027] Figure 4 The images show the XRD patterns of the β-FeOOH nanorods, PDA@β-FeOOH powder, GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional to two-dimensional layered nanohybrids prepared in Example 1.

[0028] Figure 5 The UL-94 diagrams for EP, EP / 7% GO, EP / 7% β-FeOOH, and EP / 7% GA@PDA@β-FeOOH in Example 4 are shown.

[0029] Figure 6 This is a graph showing the flexural strength and tensile flexural modulus of EP, EP / 7% GO, EP / 7% β-FeOOH, and EP / 7% GA@PDA@β-FeOOH in Example 4. Detailed Implementation

[0030] To better understand the present invention, specific embodiments are given below for further explanation. It should be noted that the following embodiments should not be construed as limiting the scope of protection of the present invention, that is, the present invention is not limited to the following embodiments.

[0031] Example 1 A method for preparing one-dimensional and two-dimensional layered nanohybrids of GA@PDA@β-FeOOH includes the following steps: (1) 180 mL of sulfuric acid, 20 mL of phosphoric acid mixture slowly poured into a reactor containing 1.5 g of graphite powder, stirring evenly; then, slowly add 9.0 g of potassium permanganate powder, the process to keep the mixture temperature not more than 50℃; stirring at 50℃ for 6 hours, add dilute hydrogen peroxide solution until no bubbles; continue to stir at 50℃ for 2 hours, cooling to room temperature, the suspension at 10000 rpm centrifugal speed for 5 minutes, deionized water washing 7 times after freeze drying 2 days, obtain GO nanosheet; (2) preparation of 0.1M FeCl3·6H2O aqueous solution, placed in the reaction kettle 120℃ hydrothermal reaction 12 hours; cooling to room temperature after centrifugal separation, deionized water washing 3 times after drying, obtain β-FeOOH nanorod; (3) 2.0 g of GO nanosheet obtained in step (1) and 120 mL of toluene solution; quickly add 12 mL of (3-aminopropyl) triethoxysilane (APTES) solution, mix evenly; stirring at 70℃ for 12 hours in nitrogen atmosphere; cooling to room temperature after centrifugal separation, anhydrous ethanol washing 3 times after drying, obtain GO-APTES powder; (4) 3.0 g of β-FeOOH nanorod obtained in step (2) is dispersed in 300 mL of Tris-HCl buffer solution (concentration 10 mM), 0.6 g of dopamine hydrochloride is added, stirring at room temperature for 12 hours, centrifugal separation after reaction, deionized water washing 3 times after drying, obtain PDA@β-FeOOH powder; (5) 1.5 g of PDA@β-FeOOH powder obtained in step (4) is added to the solution of 300 mL of 1 mg / L GO-APTES aqueous solution obtained in step (3), stirring at room temperature for 24 hours, centrifugal drying to obtain GO@PDA@β-FeOOH powder.

[0032] Example 2 (1) 190 mL of sulfuric acid, 30 mL of phosphoric acid mixture slowly poured into a reactor containing 1.8 g of graphite powder, stirring evenly; then, slowly add 10.0 g of potassium permanganate powder, the process to keep the mixture temperature not more than 50℃; stirring at 50℃ for 6 hours, add dilute hydrogen peroxide solution until no bubbles; continue to stir at 50℃ for 3 hours, cooling to room temperature, the suspension at 10000 rpm centrifugal speed for 6 minutes, deionized water washing 7 times after freeze drying 1 day, obtain GO nanosheet; (2) preparation of 0.1M FeCl3·6H2O aqueous solution, placed in the reaction kettle 120℃ hydrothermal reaction 14 hours; cooling to room temperature after centrifugal separation, deionized water washing 3 times after drying, obtain β-FeOOH nanorod; (3) Take 0.5 g GO nanosheet and mix with 120 mL toluene solution; quickly add 3 mL APTES solution, mix evenly; stir at 70°C for 13 hours in nitrogen atmosphere; centrifugal separation after cooling to room temperature, dry after washing with anhydrous ethanol for 3 times, obtain GO-APTES powder; (4) Take 2.0 g β-FeOOH nanorod and disperse in 250 mL Tris-HCl buffer solution (concentration 10 mM), add 0.4 g dopamine hydrochloride, stir at room temperature for 14 hours, centrifugal separation after reaction, dry after washing with deionized water for 3 times, obtain PDA@β-FeOOH powder; (5) Take GO-APTES powder and prepare 1 mg / L 100 mL aqueous solution, add 0.5 g PDA@β-FeOOH powder obtained in step (4) in the solution, stir at room temperature for 26 hours, centrifugal dry to obtain GA@PDA@β-FeOOH powder.

[0033] Example 3 (1) Pour 170 mL sulfuric acid, 30 mL phosphoric acid mixture into the reactor containing 1.5 g graphite powder slowly, stir evenly; then, slowly add 10.0 g potassium permanganate powder, keep the temperature of the mixture below 50°C during the process; stir at 50°C for 5 hours, add diluted hydrogen peroxide solution until no bubbles are generated; continue to stir at 50°C for 3 hours, cool to room temperature, centrifugal separation of the suspension at 10000 rpm for 5 minutes, dry after washing with deionized water for 7 times, freeze dry for 3 days, obtain GO nanosheet; (2) Prepare 0.1 M FeCl3·6H2O aqueous solution, place in the reaction kettle, hydrothermal reaction at 125°C for 12 hours; centrifugal separation after cooling to room temperature, dry after washing with deionized water for 3 times, obtain β-FeOOH nanorod; (3) Take 0.5 g GO nanosheet and mix with 60 mL toluene solution; quickly add 3 mL APTES solution, mix evenly; stir at 70°C for 14 hours in nitrogen atmosphere; centrifugal separation after cooling to room temperature, dry after washing with anhydrous ethanol for 3 times, obtain GO-APTES powder; (4) Take 1.0 g β-FeOOH nanorod and disperse in 100 mL Tris-HCl buffer solution (concentration 10 mM), add 0.2 g dopamine hydrochloride, stir at room temperature for 11 hours, centrifugal separation after reaction, dry after washing with deionized water for 3 times, obtain PDA@β-FeOOH powder; (5) Take GO-APTES powder and prepare 2 mg / L 100 mL aqueous solution, add 1.0 g PDA@β-FeOOH powder obtained in step (4) in the solution, stir at room temperature for 22 hours, centrifugal dry to obtain GA@PDA@β-FeOOH powder.

[0034] Comparative Example 1 The bisphenol A type epoxy resin (E-44) and the epoxy resin curing agent diamino diphenyl methane (DDM) were mixed in a ratio of 4:1, then degassed for 30 min, poured into a preheated mold and cured at 100°C for 2h, 150°C for 2h, and then cooled to be demolded to obtain the epoxy resin product A.

[0035] Example 4 The GO nanosheets, β-FeOOH nanorods, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids prepared in Example 1 were mixed with the bisphenol A type epoxy resin (E-44) and the epoxy resin curing agent diamino diphenyl methane (DDM) in a ratio of 7:75:25, wherein the GO nanosheets, β-FeOOH nanorods, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids were first dispersed with acetone by ultrasonic, then the epoxy resin was added and stirred, then degassed for 30 min, poured into a preheated mold and cured at 100°C for 2h, 150°C for 2h, and then cooled to be demolded to obtain EP / 7% GO, EP / 7% β-FeOOH, and EP / 7% GA@PDA@β-FeOOH.

[0036] The GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids prepared in Example 1 were mixed with the bisphenol A type epoxy resin (E-44) and the epoxy resin curing agent diamino diphenyl methane (DDM) in a ratio of 6:80:20, poured into a preheated mold and cured at 100°C for 2h, 150°C for 2h, and then cooled to be demolded to obtain EP / 6% GA@PDA@β-FeOOH.

[0037] Figure 1 The (a), (b), (c), (d), (e), and (f) in FIG. 1 are respectively the SEM image of the β-FeOOH nanorods prepared in step (2) of Example 1, the PDA@β-FeOOH powder prepared in step (4) and its local magnification, the GO nanosheets prepared in step (1), the GO-APTES powder prepared in step (3), and the TEM image of the GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids prepared in step (5) of Example 1. The synthesized β-FeOOH presents a regular rod-like morphology, and the magnified view clearly presents the uniform PDA coating wrapped around the β-FeOOH nanorods, confirming the successful preparation of PDA@β-FeOOH. The original graphene oxide (GO) presents a significant layered stacking structure (d) in FIG. 1, while the GO-APTES has a thinner and more dispersed layered structure (e) in FIG. 1. Figure 1 Figure 1 Figure 1 ​​(f) shows the effective integration of rod-like PDA@β-FeOOH with layered GO-APTES. After modification by PDA@β-FeOOH, GO-APTES retains its inherent layered structure, and PDA@β-FeOOH nanoparticles are densely anchored on the surface of nanosheets, effectively inhibiting the aggregation of nanosheets, which confirms the successful combination of one-dimensional β-FeOOH and two-dimensional GO materials.

[0038] Figure 2 The infrared spectra of GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids prepared in Example 1 can be seen that the FTIR spectrum of graphene oxide shows the following characteristic absorption bands: 3432 cm - ¹ (O-H stretching vibration), 1732 cm - ¹ (C=O stretching vibration of carboxyl), 1227 cm - ¹ (C-OH bending vibration of hydroxyl), and 1053 cm - ¹ (C-O-C stretching vibration of epoxy groups), which confirm the successful oxidation of graphite powder. In the GO-APTES spectrum, the intensity of O-H stretching vibration is weakened, and two clear characteristic peaks can be observed: 2935 cm - ¹ corresponding to the -CH2 group of APTES, 1630 cm - ¹ corresponding to the -C-NH-C- bond formed by the reaction of GO epoxy groups with APTES amine groups. In addition, the newly appearing peak at 1030 cm - ¹ corresponds to the Si-O-Si bond generated by the hydrolysis of APTES in water. These observations indicate that APTES successfully covalently modifies GO. GA@PDA@β-FeOOH exhibits β-FeOOH characteristic peaks at 694 cm - ¹ and 636 cm - ¹, while a new phenolic hydroxyl stretching vibration peak appears at 1213 cm - ¹, confirming that PDA@β-FeOOH is successfully loaded on GA nanosheets.

[0039] Figure 3The thermal decomposition curves of the β-FeOOH nanorods, PDA@β-FeOOH powder, GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids prepared in Example 1 under nitrogen conditions can be seen that GO exhibits thermal instability and rapidly degrades below 200°C due to the decomposition of unstable oxygen functional groups. In contrast, GO-APTES presents gradual degradation below 200°C, and the mass loss is significantly reduced at 800°C, mainly because the functionalization treatment greatly improves the thermal stability of GO. β-FeOOH has good thermal stability, and PDA@β-FeOOH has slightly decreased thermal stability compared to unmodified β-FeOOH, with an additional mass loss of about 2%, which is mainly due to the loss of the surface-coated PDA. The mass loss of GA@PDA@β-FeOOH at 800°C is 25.9%, and the thermal stability is enhanced.

[0040] Figure 4 The XRD patterns of the β-FeOOH nanorods, PDA@β-FeOOH powder, GO nanosheets, GO-APTES powder, and GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrids prepared in Example 1 can be seen that GO presents a (001) peak characteristic of graphene oxide at 2θ = 10.60°, and the (002) peak characteristic of graphite disappears, confirming that the graphite powder is completely oxidized. APTES modification causes the diffraction peak of GO to shift to 2θ = 9.35°, indicating that the interlayer spacing is successfully increased by functionalization. The observed main characteristic peaks of β-FeOOH can be attributed to tetragonal FeOOH (JCPDS #34-1266), confirming the successful synthesis of β-FeOOH nanorods. PDA@β-FeOOH does not have additional diffraction peaks due to the amorphous nature of the thin PDA coating layer. PDA@β-FeOOH is loaded on GO-APTES nanosheets, masking the diffraction peaks of GO-APTES.

[0041] Figure 5 The UL-94 diagram of EP, EP / 7% GO, EP / 7% β-FeOOH, and EP / 7% GA@PDA@β-FeOOH in Example 4 can be seen that the flame retardancy of pure polyethylene (EP) is limited, and the continuous burning time after initial ignition exceeds 140 seconds, and a large amount of melt droplets appear after 60 seconds, and it fails to pass the UL-94 test. After adding 7% GO, the flame retardancy is slightly improved, and it still fails to pass the UL-94 test, with a continuous burning time of more than 60 seconds after initial ignition. The flame retardancy is further improved after adding 7% β-FeOOH, but it still only reaches V-1 level. The EP / GA@PDA@β-FeOOH composite material exhibits excellent flame retardancy, and after two rounds of burning experiments, it reaches self-extinguishing state in only 8 seconds of total burning time, and the UL-94 level is V-0 level.

[0042] Figure 6 For the tensile strength and tensile modulus graph of EP, EP / 7% GO, EP / 7% β-FeOOH, EP / 7% GA@PDA@β-FeOOH in Example 4, it can be seen that the bending strength of EP / β-FeOOH is increased by 15.3% compared with pure EP, which indicates that β-FeOOH has a significant positive effect on the mechanical properties of EP. The bending modulus of EP / GO composite material reaches 2741.92 MPa, which is increased by 17.4% compared with pure EP. Finally, the bending strength and bending modulus of EP / 7% GA@PDA@β-FeOOH composite material are not much different from those of pure EP, which indicates that GA@PDA@β-FeOOH basically does not affect the mechanical properties of the composite material.

Claims

1. A method for preparing a GdPDAβ-FeOOH one-dimensional-two-dimensional layered structure nanohybrid, characterized in that, Comprising the following steps: (1) Synthesis of GO: a mixture of sulfuric acid and phosphoric acid is slowly poured into a reactor containing graphite powder and stirred uniformly; potassium permanganate powder is slowly added, and the temperature of the mixture is kept below 50°C during this process; a first stirring reaction is performed, and diluted hydrogen peroxide solution is added until no bubbles are generated; a second stirring reaction is performed, and the mixture is cooled to room temperature, centrifuged, washed, and freeze-dried to obtain GO nanosheets; (2) Synthesis of β-FeOOH: an aqueous solution of FeCl3·6H2O is prepared and subjected to hydrothermal reaction in a reaction kettle; the mixture is cooled to room temperature, centrifuged, washed, and dried to obtain β-FeOOH nanorods; (3) Preparation of GO-APTES: the GO nanosheets obtained in step (1) are mixed with toluene solution; APTES solution is quickly added and mixed uniformly; the mixture is stirred under a nitrogen atmosphere; the mixture is cooled to room temperature, centrifuged, washed, and dried to obtain GO-APTES powder; (4) Preparation of PDA@β-FeOOH: the β-FeOOH nanorods obtained in step (2) are dispersed in a Tris-HCl buffer solution, and dopamine hydrochloride is added; the mixture is stirred at room temperature, centrifuged, washed, and dried to obtain PDA@β-FeOOH powder; (5) Preparation of GA@PDA@β-FeOOH: the GO-APTES powder obtained in step (3) is prepared into an aqueous solution, and the PDA@β-FeOOH powder obtained in step (4) is added to the solution and stirred at room temperature; the mixture is centrifuged and dried to obtain GA@PDA@β-FeOOH powder.

2. The production method according to claim 1, characterized by, In step (1), the temperature of the first and second stirring reactions is 50-60°C, the first stirring reaction time is 5-7 hours, and the second stirring reaction time is 1-3 hours; the freeze-drying time is 1-2 days.

3. The preparation method according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 115-125°C, and the reaction time is 10-14 hours; the concentration of the aqueous FeCl3·6H2O solution is 0.1-0.4 M.

4. The method of claim 1, wherein, In step (3), the stirring reaction temperature is 60-80°C, and the reaction time is 10-14 hours; the mass-to-volume ratio of the GO nanosheets to APTES is 1:5-7 g / mL.

5. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of the β-FeOOH nanorods to dopamine hydrochloride is 1:0.1-0.5, and the concentration of the Tris-HCl buffer solution is 5-15 mM.

6. The method of claim 1, wherein, In step (5), the mass ratio of GO-APTES to PDA@β-FeOOH is 1:5-10.

7. A method for preparing a flame retardant epoxy resin based on GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid, characterized in that, Comprising the following steps: (a) dispersing the GA@PDA@β-FeOOH powder obtained in claim 1 in acetone and subjecting to ultrasonic treatment; (b) adding the dispersion to an epoxy resin and stirring; (c) adding diamino diphenyl methane and mixing uniformly before pouring into a mold; (d) stepwise curing to obtain an epoxy resin / GA@PDA@β-FeOOH composite material; The adding amount of the GA@PDA@β-FeOOH is 1-10 wt% of the mass of the epoxy resin; and the stage curing of step (d) is: first curing at 100-110℃ for 1.5-2.5 hours, and then curing at 150-160℃ for 1.5-2.5 hours.

8. The GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid obtained by the preparation method of any one of claims 1-6.

9. An epoxy resin flame retardant based on the GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid obtained by the preparation method of claim 7.

10. The application of the GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid of claim 8 or the epoxy resin flame retardant based on the GA@PDA@β-FeOOH one-dimensional-two-dimensional layered structure nanohybrid of claim 9 in paints, adhesives, electronic component encapsulants.

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