An epoxy resin flame retardant of interlayer-interface double modified nickel-iron hydrotalcite and a preparation method and application thereof

Abstract

The application discloses an interlayer-interfacial double-modified nickel-iron hydrotalcite epoxy resin flame retardant and a preparation method and application thereof. The flame retardant takes nickel-iron hydrotalcite as a core, forms interlayer-interfacial double-modified nickel-iron hydrotalcite (NFNDC(S)) through interlayer modification of sodium dodecyl sulfate (SDS) and interfacial grafting of DOPO after acyl chloride modification. The LDH interlayer anion exchange characteristics are utilized to hydrothermally synthesize SDS intercalated NiFeLDH in one step; the abundant hydroxyl groups on the LDH surface are grafted with silane coupling agent APTES to provide active sites for the introduction of DOPO; the acyl chloride modified DOPO is reacted with the amino group of KH-550 to introduce DOPO and build the interlayer-interfacial double-modified nickel-iron hydrotalcite. The obtained NFNDC(S) particles have good dispersibility in an epoxy resin matrix. The flame retardant can be applied to the epoxy resin to significantly improve the thermal stability and flame retardant performance of the composite material.

Description

Technical Field

[0001] This invention belongs to the technical field of epoxy resin flame retardants, specifically relating to an epoxy resin flame retardant with interlayer-interface dual modification of nickel-iron hydrotalcite, its preparation method, and its application. Background Technology

[0002] Epoxy resin (EP) has become an indispensable basic material in fields such as electronics, aerospace, transportation, and new energy due to its excellent bonding strength, mechanical properties, chemical stability, and electrical insulation. However, its extremely high flammability and the intense exothermic reaction, large amounts of smoke, and toxic gas release during combustion pose serious fire hazards, greatly limiting its further application in cutting-edge and safety-sensitive fields. Therefore, developing high-performance flame-retardant epoxy resin composites is not only an important material modification topic, but also a key technological challenge concerning life and property safety and the development of strategic industries.

[0003] Currently, the mainstream method for improving the flame retardant properties of epoxy resins is by adding flame retardants. Commercial flame retardants are mainly classified into halogen-based (such as bromine and chlorine compounds), phosphorus-based organic compounds, and nitrogen-based additives. However, halogen-based flame retardants release highly toxic fumes during combustion, which contradicts current environmental trends; while phosphorus-based and nitrogen-based flame retardants require high addition levels (usually exceeding 20 wt%) to achieve effective flame retardancy. This not only increases costs but also leads to agglomeration due to poor dispersibility, severely impairing the material's mechanical properties. These drawbacks significantly limit the application of epoxy resins in the fireproofing field.

[0004] Layered double hydroxides (LDHs), commonly known as hydrotalcite, are environmentally friendly halogen-free flame retardants with broad application prospects in the flame-retardant modification of epoxy resins. However, the high interlayer charge density and strong interactions between hydroxide flakes make aggregation easy and delamination difficult. Furthermore, the hydrophilicity of LDH and the hydrophobicity of the polymer result in an incompatible interface between them. Therefore, the flame-retardant effect of LDH on polymers largely depends on its dispersion state and surface properties. Through appropriate modification and compounding processes, LDH can effectively improve the flame-retardant properties and thermal stability of epoxy resins while reducing the generation of toxic fumes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an epoxy resin flame retardant with interlayer-interface dual-modified nickel-iron hydrotalcite particles, which has good compatibility with epoxy resin and has excellent flame retardant effect when applied, in order to overcome the shortcomings of the prior art.

[0006] This invention develops a novel flame retardant strategy: Sodium dodecyl sulfate (SDS) is used as a hydrophobic agent to first modify LDH from hydrophilic to hydrophobic, improving its compatibility with epoxy resin and introducing the flame retardant element S; the silane coupling agent APTES improves the dispersibility of LDH and provides active sites for the subsequent introduction of DOPO; DOPO, as a commonly used and excellent phosphorus-based flame retardant, is introduced into the LDH flame retardant system through the bridging effect of APTES, thereby improving the overall flame retardant performance.

[0007] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: A method for preparing an epoxy resin flame retardant with interlayer-interface dual-modified NiFe-LDH particles includes the following steps: (1) Synthesis of NF-SDS: Ni(NO) 3)2 ·6H2O, Fe(NO3)3·9H2O, sodium dodecyl sulfate, NH4F, and urea were added to deionized water and stirred until uniformly dispersed. The mixture was then added to a reaction vessel and placed in an oven. The reaction was heated at 110-130℃ for 10-14 hours. The suspension was centrifuged at 7000-9000 rpm for 3-5 minutes. The precipitate was washed alternately with anhydrous ethanol and deionized water and dried at 60-80℃ for 10-14 hours to obtain SDS-intercalated NF-SDS. (2) Preparation of DOPA: Dissolve DOPO in ethanol solution to obtain solution A, take H2O2 as solution B, add solution B dropwise to solution A, stir at 70-90℃ for 10-14 hours, rotary evaporate at 60-80℃ and then vacuum to obtain crude product, add petroleum ether and ethyl acetate to make slurry to obtain DOPA; (3) Preparation of DOPO-Cl: Place DOPA in a round-bottom flask, add excess thionyl chloride, react at 70-90℃ for 16-20 hours, and rotary evaporate at 60-80℃ to obtain DOPO-Cl; (4) Preparation of NF-SDS-NH2: The NF-SDS obtained in step (1) is added to a round-bottom flask, and the silane coupling agent APTES is added with toluene as solvent. The mixture is stirred at 100-120℃ for 22-26 hours. After the reaction is completed, the mixture is centrifuged twice with toluene and anhydrous ethanol alternately, and then dried to obtain NF-SDS-NH2. (5) Preparation of NFNDC(S): DOPO-Cl, NF-SDS-NH2 and triethylamine (TEA) were added to DMF and stirred under argon protection at 70-90℃ for 6-10 hours. After the reaction was completed, the mixture was centrifuged and washed three times with anhydrous ethanol to obtain NFNDC(S) three-dimensional hydrotalcite particles, which are epoxy resin flame retardants of interlayer-interface dual-modified NiFe-LDH particles.

[0008] Preferably, in step (2), the molar ratio of DOPO to H2O2 is 1:(1.1-1.3), and the mass-volume ratio of DOPO to H2O2 is (0.1-0.3):1 g / mL.

[0009] Preferably, in step (2), the volume ratio of petroleum ether to ethyl acetate is 1:(5-15), more preferably 1:10. Preferably, in step (3), the mass-to-volume ratio of DOPA to thionyl chloride is 1:(2.5-4.5) g / mL.

[0010] Preferably, in step (4), the mass-to-volume ratio of NF-SDS to toluene is 1:(40-80) g / mL. The mass-to-volume ratio of NF-SDS to APTES is 1:(1.5-2.5) g / mL.

[0011] Preferably, in step (5), the mass ratio of NF-SDS-NH2 to DOPO-Cl is 1:(2-4), the mass-volume ratio of NF-SDS-NH2 to triethylamine is 1:(6-8) g / mL, and the mass-volume ratio of NF-SDS-NH2 to DMF is 1:(80-120) g / mL.

[0012] An epoxy resin flame retardant based on NFNDC(S) three-dimensional hydrotalcite particles is an epoxy resin / NFNDC(S) composite material obtained by combining NFNDC(S) three-dimensional hydrotalcite particles with epoxy resin. The preparation method includes the following steps: (a) Disperse the NFNDC(S) three-dimensional hydrotalcite particles prepared by the above method in acetone and sonicate for 0.4-0.6 hours; (b) Add the dispersion to epoxy resin preheated at 80-85℃ and stir for 1-2 hours; (c) Add 20%-30% of diaminodiphenylmethane (DDM) by weight of epoxy resin, mix well and then inject into the mold; (d) Step curing: First cure at 100-110℃ for 1.5-2.5 hours, then cure at 150-160℃ for 1.5-2.5 hours to obtain epoxy resin / NFNDC(S) composite material.

[0013] Preferably, the amount of NFNDC(S) three-dimensional hydrotalcite particles added is 1-10 wt% of the epoxy resin mass.

[0014] The above method yields an NFNDC(S) three-dimensional hydrotalcite particle, which has a three-dimensional hydrotalcite structure with interlayer-interface dual modification, consisting of a NiFe-LDH host, interlayer intercalated SDS, an interface-modified APTES intermediate connecting layer, and covalently grafted DOPO. This structure enhances its hydrophobicity and improves its compatibility with the epoxy resin matrix by replacing interlayer carbonate ions with anion-exchanged SDS, and further introduces hydrophobic alkyl segments by grafting DOPO with the silane coupling agent APTES.

[0015] The above method yields an epoxy resin / NFNDC(S) composite material, in which the epoxy resin is a continuous phase, and NFNDC(S) three-dimensional hydrotalcite particles are uniformly dispersed and firmly bonded by chemical bonding. These particles are composed of a NiFe-LDH matrix, intercalated SDS, interface-modified APTES, and covalently grafted DOPO. Their unique structure not only endows the particles with higher compatibility with the polymer, but also helps to alleviate the decline in the mechanical properties of the composite material.

[0016] The NFNDC(S) three-dimensional hydrotalcite particles and epoxy resin / NFNDC(S) composite materials prepared by this invention can be applied to coatings, adhesives, electronic component encapsulants and civil engineering industries.

[0017] The flame retardant prepared in this invention is based on NiFe-LDH, and organic-inorganic hybrid three-dimensional hydrotalcite particles NFNDC(S) are formed through interlayer-interface dual modification. Specifically, utilizing the exchangeable anion properties of LDH interlayers, the easily exchangeable NO3- is... - and CO3 2- Replacing LDH with sodium dodecyl sulfate (SDS), which has a long aliphatic chain, improves the dispersibility of LDH particles, enhances agglomeration, and increases their hydrophobicity. Subsequently, by reacting the abundant hydroxyl groups on the LDH surface with the silane coupling agent APTES, abundant active sites for the introduction of DOPO are provided, further improving the surface hydrophobicity. The resulting NFNDC(S) three-dimensional hydrotalcite particles exhibit good dispersibility in the epoxy resin matrix. Applying this flame retardant to epoxy resin significantly improves the thermal stability and flame retardant properties of the composite material, for example, increasing its flame retardant rating (adding 7% NFNDC(S) can improve the vertical flammability rating of the epoxy resin from NR to V-0). Its flame retardant mechanism is mainly attributed to the synergistic effect of NiFe-LDH, SDS, and DOPO, including catalytic char formation, formation of a dense char layer, and gas-phase free radical quenching effects. The flame retardant provided by this invention has advantages such as low addition amount, high flame retardant efficiency, and minimal negative impact on the mechanical properties of the matrix.

[0018] Compared with existing technologies, the beneficial effects of the present invention are as follows: This invention constructs a three-dimensional hydrotalcite particle flame retardant with NiFe-LDH as the main component, SDS as the interlayer modifier, and DOPO as the interface modifier, achieving multiple synergistic flame retardant effects. NiFe-LDH catalyzes the cross-linking and carbonization of the polymer matrix, enhancing the density of the char layer. Its thermal decomposition absorbs a large amount of heat, and the released water vapor can reduce the concentration of combustible gases and oxygen. DOPO efficiently captures free radicals and participates in the LDH phase transition to form a denser char layer. When the obtained flame retardant is added at 7 wt%, the UL-94 rating of the epoxy resin composite material can reach the V-0 level, and the LOI increases from 22.3% to 28.2%. At the same time, due to the improvement of particle agglomeration by SDS and the improvement of compatibility by DOPO, its mechanical strength is not significantly different from that of pure EP. This invention solves the technical bottleneck of traditional flame retardants where high addition amounts (>20 wt%) damage mechanical properties and process adaptability. Attached Figure Description

[0019] Figure 1 These are scanning electron microscope images of NiFe-LDH, NF-SDS, and NFNDC(S) prepared in Example 1.

[0020] Figure 2 The infrared spectra of NiFe-LDH, NF-SDS, and NFNDC(S) prepared in Example 1 are shown.

[0021] Figure 3 These are the thermal decomposition curves of NiFe-LDH, NF-SDS, and NFNDC(S) prepared in Example 1 under nitrogen conditions.

[0022] Figure 4 The images show the XRD patterns of NiFe-LDH, NF-SDS, and NFNDC(S) prepared in Example 1.

[0023] Figure 5 These are the LOI and UL-94 figures for EP / (7wt%)NF, EP / (7wt%)NF-SDS, and EP / (7wt%)NFNDC(S) in Example 4.

[0024] Figure 6 The diagram shows the bending strength and bending modulus of EP7 / NF, EP7 / NF-SDS, and EP7 / NFNDC(S) in Example 4. Detailed Implementation

[0025] 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.

[0026] Example 1 (1) Weigh Ni(NO3)2 4.5 g of ·6H2O, 2.2 g of Fe(NO3)3·9H2O, 4.05 g of sodium dodecyl sulfate (SDS), 4.12 g of NH4F, 6.5 g of urea, and 550 ml of deionized water were stirred until uniformly dispersed. The mixture was then dispensed into a reaction vessel and placed in an oven. The reaction was carried out at 120°C for 12 hours. The suspension was centrifuged at 8000 rpm for 4 minutes. The precipitate was washed alternately with anhydrous ethanol and deionized water and dried at 70°C for 12 hours to obtain yellow NF-SDS powder with SDS intercalation. The unmodified NiFe-LDH (NF) was obtained without the addition of SDS.

[0027] (2) Dissolve 21.6 g DOPO in 70 ml ethanol solution to prepare solution A. Take 100 ml H2O2 as solution B. Add solution B dropwise to solution A. Refrigerate at 80℃ for 12 hours. After rotary evaporation at 70℃, vacuum is applied to obtain crude product. Add petroleum ether and ethyl acetate to make a slurry (the volume ratio of petroleum ether to ethyl acetate is 1:10). Transfer the precipitate to an oven and dry at 70℃ for 12 hours to obtain white powder DOPA.

[0028] (3) Take 2.16 g of DOPA obtained in step (2) and place it in a round-bottom flask. Add 10 ml of thionyl chloride and reflux at 80 °C. Rotary evaporation yields a pale yellow solid DOPO-Cl.

[0029] (4) Take 0.5 g of NF-SDS obtained in step (1) and add it to a round bottom flask. Disperse it in 30 ml of toluene solution and add 1 ml of silane coupling agent APTES. Reflux the mixture at 110 °C for 24 hours. After the reaction is complete, centrifuge twice with toluene and anhydrous ethanol at 8000 rpm. Transfer the precipitate to an oven and dry it at 70 °C for 12 hours to obtain a light yellow powder NF-SDS-NH2.

[0030] (5) Take 4.32 g DOPO-Cl, 2 g NF-SDS-NH2 and 15 ml triethylamine (TEA) and add them to 200 ml DMF. Stir at 80℃ under argon protection for 8 hours. After the reaction, the mixture is centrifuged at 8000 rpm and washed 3 times with anhydrous ethanol. The precipitate is transferred to an oven and dried at 70℃ for 12 hours to obtain light yellow powder NFNDC(S) three-dimensional hydrotalcite particles.

[0031] Example 2 (1) Weigh Ni(NO 3)24.6 g of ·6H2O, 2.1 g of Fe(NO3)3·9H2O, 4.05 g of sodium dodecyl sulfate (SDS), 4.0 g of NH4F, 6.4 g of urea, and 540 ml of deionized water were stirred until uniformly dispersed. The mixture was then dispensed into a reaction vessel and placed in an oven. The reaction was carried out at 120°C for 8 hours. The suspension was centrifuged at 8000 rpm for 4 minutes. The precipitate was washed alternately with anhydrous ethanol and deionized water and dried at 80°C for 16 hours to obtain yellow NF-SDS powder with SDS intercalation. The unmodified NiFe-LDH (NF) was obtained without the addition of SDS.

[0032] (2) Dissolve 21.6 g DOPO in 80 ml ethanol solution to prepare solution A. Take 100 ml H2O2 as solution B. Add solution B dropwise to solution A. Refrigerate at 80℃ for 16 hours. After rotary evaporation at 80℃, vacuum is applied to obtain crude product. Add petroleum ether and ethyl acetate to make a slurry (the volume ratio of petroleum ether to ethyl acetate is 1:5). Transfer the precipitate to an oven and dry at 80℃ for 16 hours to obtain white powder DOPA.

[0033] (3) Take 4.32 g of DOPA obtained in step (2) and place it in a round-bottom flask. Add 18 ml of thionyl chloride and reflux at 80 °C. Rotary evaporation yields a pale yellow solid DOPO-Cl.

[0034] (4) Take 1 g of NF-SDS obtained in step (1) and add it to a round bottom flask. Disperse it in 50 ml of toluene solution and add 2 ml of silane coupling agent APTES. Reflux the mixture at 80 °C for 24 hours. After the reaction is complete, centrifuge twice with toluene and anhydrous ethanol at 8000 rpm. Transfer the precipitate to an oven and dry it at 80 °C for 16 hours to obtain a light yellow powder NF-SDS-NH2.

[0035] (5) Take 2.16 g DOPO-Cl, 1 g NF-SDS-NH2 and 10 ml triethylamine (TEA) and add them to 80 ml DMF. Stir at 80℃ under argon protection for 12 hours. After the reaction, the mixture is centrifuged at 8000 rpm and washed 3 times with anhydrous ethanol. The precipitate is transferred to an oven and dried at 80℃ for 16 hours to obtain light yellow powder NFNDC(S) three-dimensional hydrotalcite particles.

[0036] Example 3 (1) Weigh Ni(NO 3)24.5 g of ·6H2O, 2 g of Fe(NO3)3·9H2O, 4 g of sodium dodecyl sulfate (SDS), 4.2 g of NH4F, 6.5 g of urea, and 500 ml of deionized water were stirred until uniformly dispersed. The mixture was then dispensed into a reaction vessel and placed in an oven. The reaction was carried out at 110°C for 10 hours. The suspension was centrifuged at 8000 rpm for 5 minutes. The precipitate was washed alternately with anhydrous ethanol and deionized water and dried at 90°C for 10 hours to obtain yellow NF-SDS powder with SDS intercalation. The unmodified NiFe-LDH (NF) was obtained without the addition of SDS.

[0037] (2) Dissolve 21.6 g DOPO in 120 ml ethanol solution to prepare solution A. Take 90 ml H2O2 as solution B. Add solution B dropwise to solution A. Refrigerate at 80℃ for 14 hours. After rotary evaporation at 60℃, vacuum is applied to obtain crude product. Add petroleum ether and ethyl acetate to make a slurry (the volume ratio of petroleum ether to ethyl acetate is 1:15). Transfer the precipitate to an oven and dry at 80℃ for 12 hours to obtain white powder DOPA.

[0038] (3) Take 4.32 g of DOPA obtained in step (2) and place it in a round-bottom flask. Add 22 ml of thionyl chloride and reflux at 80 °C. Rotary evaporation yields a pale yellow solid DOPO-Cl.

[0039] (4) Take 1.2 g of NF-SDS obtained in step (1) and add it to a round bottom flask. Disperse it in 70 ml of toluene solution and add 2.4 ml of silane coupling agent APTES. Reflux the mixture at 100 °C for 24 hours. After the reaction is complete, centrifuge twice with toluene and anhydrous ethanol at 8000 rpm. Transfer the precipitate to an oven and dry it at 60 °C for 10 hours to obtain a light yellow powder NF-SDS-NH2.

[0040] (5) Take 2.5 g DOPO-Cl, 1 g NF-SDS-NH2 and 9 ml triethylamine (TEA) and add them to 90 ml DMF. Stir at 80℃ under argon protection for 16 hours. After the reaction, the mixture is centrifuged at 8000 rpm and washed 3 times with anhydrous ethanol. The precipitate is transferred to an oven and dried at 60℃ for 24 hours to obtain light yellow powder NFNDC(S) three-dimensional hydrotalcite particles.

[0041] Comparative Example 1 Bisphenol A type epoxy resin (E-44) and epoxy resin curing agent diaminodiphenylmethane (DDM) are mixed in a ratio of 4:1, then degassed for 30 minutes, poured into a preheated mold, cured at 100℃ for 2 hours, cured at 150℃ for 2 hours, and then cooled to demold epoxy resin product A.

[0042] Example 4 The NF-SDS, unmodified NiFe-LDH (NF), and NFNDC (S) three-dimensional hydrotalcite particles prepared in Example 1 were mixed with bisphenol A type epoxy resin (E-44) and epoxy resin curing agent diaminodiphenylmethane (DDM) in a ratio of 7:80:20. The unmodified NiFe-LDH (NF), NF-SDS, and NFNDC (S) three-dimensional hydrotalcite particles were first ultrasonically dispersed with acetone, then epoxy resin was added and stirred evenly. After degassing for 30 minutes, the mixture was poured into a preheated mold and cured at 100°C for 2 hours and 150°C for 2 hours. After cooling, the mixture could be demolded to obtain EP / (7wt%)NF, EP / (7wt%)NF-SDS, and EP / (7wt%)NFNDC (S).

[0043] Figure 1 SEM images of NiFe-LDH, NF-SDS, and NFNDC(S) are shown, along with the dispersion of NF-SDS. Figure 1 As shown in (a), the synthesized NiFe-LDH exhibits a three-dimensional flower-like structure resembling a hydrangea, but the different flower-like structures agglomerate with each other, resulting in poor dispersibility. After SDS interlayer modification, the flower-like structure becomes expanded and loose, but still retains the flower-like structure, and the different flower-like structures do not agglomerate with each other, indicating good dispersibility. Figure 1 (b) indicates that the successful introduction of SDS reduced the self-agglomeration of NiFe-LDH and improved its dispersibility. After the interface modification with APTES and DOPO, the flower-like structure of NiFe-LDH was affected by the etching of the reaction byproduct HCl, transforming from a three-dimensional "flower-like" structure to a two-dimensional lamellar stacked structure. This morphological transformation also indicates the successful introduction of DOPO and APTES. Figure 1 (c) in the middle.

[0044] Figure 2 The infrared spectra of the unmodified NiFe-LDH(NF) prepared in step (1), the NF-SDS prepared in step (1), the NF-SDS-NH2 prepared in step (4), and the NFNDC(S) three-dimensional hydrotalcite particles prepared in step (5) of Example 1 are shown. It can be seen that the particles in NiFe-LDH located at 1355 cm⁻¹ are... -1 The absorption band at that point corresponds to the CO3 interlayer in the LDH. 2- The C-O vibration mode, and the peak value increases with the SO3 content of SDS. 2- Gradually disappearing due to substitution. 2820-2960 cm⁻¹ detected in SDS alkyl groups. -1 The characteristic vibrational bands also confirm the successful preparation of NF-SDS. The strong and broad vibrational center of NiFe-LDH is approximately 3478 cm⁻¹. 1 (NF-SDS is 3515 cm) 1 This can be attributed to the OH stretching vibration of the structural hydroxyl groups and the adsorption of water. In NF-SDS-NH2, 1050-1250 cm⁻¹ 1 The specific region exhibits two distinct peaks, corresponding to the tensile vibrations of Si-O, with the NH bond peak appearing at 1570 cm⁻¹. 1 This proves the successful introduction of APTES. And located at 1476 cm... 1 P=O at 757 cm and at 757 cm 1 The PO-Ph at that location also proves that DOPO has been integrated into the NFNDC(S) system.

[0045] Figure 3 The thermal decomposition curves of the three-dimensional hydrotalcite particles prepared in Example 1 (without interlayer modification), NF-SDS prepared in step (1), NF-SDS-NH2 prepared in step (4), and NFNDC(S) prepared in step (5) under nitrogen conditions show that the decomposition of pure NiFe-LDH at high temperatures mainly consists of two stages: below 240℃, the mass decrease is attributed to the removal of physically adsorbed water and interlayer water molecules; while between 240-400℃, the weight decrease is attributed to CO3. 2- The removal of -OH groups. For NF-SDS, the significant decrease in weight at 200-400℃ also indicates the successful introduction of SDS; while for NF-SDS-NH2 and NFNDC(S), the increase in residual mass also indicates that the thermal stability of the NFNDC(S) system was improved by introducing APTES and DOPO.

[0046] Figure 4The XRD patterns of NiFe-LDH, NF-SDS, NF-SDS-NH2, and NFNDC(S) are shown. As shown in the figure, the XRD curve of NiFe-LDH exhibits distinct peaks at 11.63°, 23.43°, 34.44°, 39.02°, 46.53°, 59.91°, and 61.32°, corresponding to the (003), (006), (012), (015), (0015), and (113) phase planes of NiFe-LDH, respectively, displaying the typical diffraction peaks of NiFe-LDH. After SDS interlayer modification, the (003) characteristic peak at 11.63° shifts to 3.43°, the (006) characteristic peak at 23.43° shifts to 7.18°, and the overall peak value of NiFe-LDH shifts to a lower angle, revealing that SDS successfully embeds itself into the interlayer of NiFe-LDH and expands the interlayer distance.

[0047] Figure 5 The figures show the LOI and UL-94 values ​​of the EP / (7wt%)NF, EP / (7wt%)NF-SDS, and EP / (7wt%)NFNDC(S) three-dimensional hydrotalcite particles in Example 4. It can be seen that the LOI value of pure EP is only 22.3%, and it received no UL-94 rating. After adding 7% NiFe-LDH, the LOI increased to 25.4%, but a UL-94 rating was still not obtained. Notably, the introduction of SDS and DOPO significantly improved the flame retardancy of the EP composite material, as evidenced by a gradual increase in the LOI value. The EP / (7wt%)NFNDC(S) composite material exhibited the best performance, with an LOI of 28.2% and a UL-94 rating improved from unrated to V-0.

[0048] Figure 6The diagrams show the flexural strength and flexural modulus of the EP / (7wt%)NF, EP / (7wt%)NF-SDS, and EP / (7wt%)NFNDC(S) three-dimensional hydrotalcite particles in Example 4. It can be seen that compared to pure EP (flexural strength 81.0 MPa, flexural modulus 2.76 GPa), the flexural strength (72.5 MPa) and elastic modulus (2.43 GPa) of the EP / (7wt%)NF composite are significantly lower. This may be because of the poor compatibility between NiFe-LDH and the EP matrix, and the tendency of NiFe-LDH to agglomerate. The EP / (7wt%)NF-SDS shows a significant improvement in both flexural strength (79.8 MPa) and elastic modulus (2.51 GPa) compared to EP / (7wt%)NF, demonstrating that the introduction of SDS improves the compatibility of NiFe-LDH and enhances its compatibility with the EP matrix. After the introduction of DOPO, the flexural strength (83.2 MPa) and elastic modulus (2.55 GPa) of EP / (7wt%)NFNDC(S) were further improved, and its flexural strength even exceeded that of pure EP. This is attributed to the fact that the introduction of DOPO gave the LDH interface higher compatibility with the EP matrix.

Claims

1. A three-dimensional hydrotalcite particle of NFNDC(S), characterized in that, It has a three-dimensional hydrotalcite structure with interlayer-interface dual modification, consisting of a NiFe-LDH host, interlayer intercalated SDS, interface-modified APTES intermediate connecting layer, and covalently grafted DOPO.

2. The method for preparing NFNDC(S) three-dimensional hydrotalcite particles according to claim 1, characterized in that, Includes the following steps: (1) Synthesis of NF-SDS: Ni(NO) 3)2 ·6H2O, Fe(NO3)3·9H2O, sodium dodecyl sulfate, NH4F, and urea were added to deionized water and stirred until uniformly dispersed. The mixture was then added to a reaction vessel, placed in an oven, heated, washed by centrifugation, and dried to obtain SDS-intercalated NF-SDS. (2) Preparation of DOPA: Dissolve DOPO in ethanol solution to obtain solution A, take H2O2 as solution B, add solution B dropwise to solution A, stir to react, rotary evaporate and then vacuum to obtain crude product, add petroleum ether and ethyl acetate to make slurry to obtain DOPA; (3) Preparation of DOPO-Cl: Add thionyl chloride to DOPA, stir the reaction, and rotary evaporate to obtain DOPO-Cl; (4) Preparation of NF-SDS-NH2: The NF-SDS obtained in step (1) was added to a flask, and the silane coupling agent APTES was added with toluene as solvent. The mixture was stirred and reacted, and then centrifuged to obtain NF-SDS-NH2. (5) Preparation of NFNDC(S): DOPO-Cl, NF-SDS-NH2 and triethylamine (TEA) were added to DMF, stirred and reacted, and centrifuged to obtain NFNDC(S) three-dimensional hydrotalcite particles.

3. The preparation method according to claim 2, characterized in that, In step (1), the heating reaction temperature is 110-130℃ and the reaction time is 10-14 hours, and the drying temperature is 80-110℃ and the drying time is 10-14 hours.

4. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of DOPO to H2O2 is 1:(1.1-1.3), the mass-volume ratio of DOPO to H2O2 is (0.1-0.3):1 g / mL, and the temperature of the stirring reaction is 70-100℃.

5. The preparation method according to claim 2, characterized in that, In step (3), the mass-to-volume ratio of DOPA to thionyl chloride is 1:(2.5-4.5) g / mL, the stirring reaction temperature is 70-90℃, the reaction time is 16-20 hours, and the rotary evaporation temperature is 60-80℃.

6. The preparation method according to claim 2, characterized in that, In step (4), the mass-to-volume ratio of NF-SDS to toluene is 1:(40-80) g / mL, the mass-to-volume ratio of NF-SDS to APTES is 1:(1.5-2.5) g / mL, the stirring reaction temperature is 100-120℃, and the reaction time is 22-26 hours.

7. The preparation method according to claim 2, characterized in that, In step (5), the mass ratio of NF-SDS-NH2 to DOPO-Cl is 1:(2-4), the mass-volume ratio of NF-SDS-NH2 to triethylamine is 1:(6-8) g / mL, the mass-volume ratio of NF-SDS-NH2 to DMF is 1:(80-120) g / mL, the reaction temperature is 70-90℃, and the reaction time is 6-10 hours.

8. An epoxy resin flame retardant based on NFNDC(S) three-dimensional hydrotalcite particles, characterized in that, It is an epoxy resin / NFNDC(S) composite material obtained by combining the NFNDC(S) three-dimensional hydrotalcite particles as described in claim 1 with epoxy resin.

9. The method for preparing an epoxy resin flame retardant based on NFNDC(S) three-dimensional hydrotalcite particles as described in claim 8, characterized in that, Includes the following steps: (a) Dispersing NFNDC(S) three-dimensional hydrotalcite particles in acetone and ultrasonically treating them; the amount of NFNDC(S) added is 1-10 wt% of the epoxy resin mass; (b) Add the dispersion to the epoxy resin and stir. (c) Add diaminodiphenylmethane, mix well, and then pour into the mold; (d) Step curing: First cure at 100-110℃ for 1.5-2.5 hours, then cure at 150-160℃ for 1.5-2.5 hours.

10. The application of the NFNDC(S) three-dimensional hydrotalcite particles of claim 1 or the epoxy resin flame retardant based on NFNDC(S) three-dimensional hydrotalcite particles of claim 8 in coatings, adhesives, and electronic component encapsulants.

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