CN-121991414-A - Preparation method of composite flame retardant for generating phosphorus-containing covalent organic framework network by in-situ condensation of modified MXene surface

CN121991414ACN 121991414 ACN121991414 ACN 121991414ACN-121991414-A

Abstract

The invention discloses a preparation method of a composite flame retardant for generating a phosphorus-containing covalent organic framework network by in-situ condensation of a modified MXene surface, which comprises the steps of firstly taking MXene as a substrate and realizing surface coating by self-polymerization of dopamine; and further, in an ethyl acetate/DMF system, taking 1,3, 5-benzene trimethyl acyl chloride and p-phenylenediamine as monomers, and under the conditions of low-temperature dropwise adding and subsequent reflux, constructing a covalent organic framework network on the surface of the material in situ, thereby finally obtaining the MXene/COF composite flame retardant with a multi-stage structure. The composite flame retardant realizes the efficient combination of the MXene heat shielding effect and the phosphor-containing COF carbonizing effect, and obviously enhances the multidimensional synergistic flame retardant effect. Under the condition of lower addition amount, the flame retardant promotes the formation of a compact and stable carbon layer in the combustion process of the epoxy resin, and obviously reduces the heat release rate and the smoke quantity.

Inventors

WANG ZHIRONG
YANG JUNJIE
WANG JUNLING
LING ZHIPENG
YANG JINLIANG
WANG TAO
GAO XINHUA
HUANG YAJUN

Assignees

南京工业大学

Dates

Publication Date: 20260508
Application Date: 20260120

Claims (10)

1. The preparation method of the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation of the modified MXene surface is characterized by comprising the following steps of: Step 1, dispersing MXene in a mixed solvent of deionized water and ethanol to form a uniform dispersion, dripping a pH regulator to regulate the solution to be alkalescent, then adding a certain amount of surface modifier into the solution, and continuously reacting for a period of time at room temperature; Step 2, centrifugally collecting a product after the reaction is finished, alternately washing the product with deionized water and absolute ethyl alcohol, and then carrying out vacuum drying to obtain a product P@MXene; step 3, dispersing P@MXene in a polar solvent, adding a certain amount of phosphorus-containing active grafting agent after ultrasonic dispersion for a period of time, heating and introducing protective gas for reaction for a period of time; Step 4, centrifugally collecting a product after the reaction is finished, washing the product with absolute ethyl alcohol to remove substances which are not completely reacted, and then drying the product in vacuum to obtain a product P@MXene-DOPO; Step 5, dissolving a certain amount of polyacyl chloride monomer in an organic solvent to obtain a mixed solution, then adding a certain amount of P@MXene-DOPO into the organic solvent, performing ultrasonic treatment to obtain a uniform dispersion, then slowly dripping the uniform dispersion into the mixed solution, and controlling the temperature of an ice bath in the dripping process; Step 6, taking a certain amount of diamine monomer and acid binding agent, dissolving the diamine monomer and the acid binding agent in an organic solvent to obtain a mixed solution, slowly adding the mixed solution into the mixed solution obtained in the step 5, and continuously reacting at a low temperature and a room temperature after the dripping is finished; And 7, after the reaction is finished, adding a certain amount of polar solvent into the mixed solution, heating, condensing and refluxing for reaction, centrifuging and collecting products, respectively washing the products with deionized water, absolute ethyl alcohol and acetone for multiple times, and drying in a vacuum oven after the solvent is clear and colorless to obtain the final flame retardant P@MXene-DOPO@COF.
2. The method for preparing the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation on the surface of the modified MXene according to claim 1, wherein the pH regulator in the step 1 is one of TRIS-HCl buffer solution and HEPES buffer solution, and the surface modifier is dopamine hydrochloride.
3. The preparation method of the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation on the surface of the modified MXene, which is disclosed in claim 1, is characterized in that in the step 3, the polar solvent is one of N, N-dimethylformamide and N, N-dimethylacetamide, the phosphorus-containing active grafting agent is one of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-glycidyl propionate, and the protective gas is one of nitrogen and argon.
4. The preparation method of the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation on the surface of modified MXene, which is disclosed in claim 1, is characterized in that in step 5, the polyacyl chloride monomer is one of 1,3, 5-benzene trimethyl acyl chloride, 1, 4-benzene dicarboxyl chloride and pyromellitic chloride, and the organic solvent is one of ethyl acetate, dichloromethane and tetrahydrofuran.
5. The method for preparing the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation on the surface of the modified MXene according to claim 1, wherein the diamine monomer in the step 6 is one of p-phenylenediamine, o-phenylenediamine, m-phenylenediamine and diaminobiphenyl, and the acid binding agent is one of triethylamine, tripropylamine, pyridine and N, N-diisopropylethylamine.
6. The preparation method of the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation on the surface of modified MXene, which is disclosed in claim 1, is characterized in that the drying process under the vacuum condition after the product is washed is that the final product P@MXene-DOPO@COF powder is obtained by drying the product in a vacuum oven at 50-70 ℃ for 12-48 hours.
7. The preparation method of the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation of the surface of modified MXene, which is disclosed in claim 1, is characterized in that the mass ratio of MXene to the surface modifier in step 1 is 1 (0.2-0.6), the mass ratio of P@MXene to the phosphorus-containing active grafting agent in step 3 is 1 (0.4-0.8), and the mass ratio of P@MXene-DOPO to the polyacyl chloride monomer, diamine monomer and acid-binding agent in steps 5 and 6 is 1 (1-3): (0.3-1): (2-3.5).
8. The method for preparing the composite flame retardant for generating the phosphorus-containing covalent organic framework network by in-situ condensation on the surface of modified MXene according to claim 7, which is characterized by comprising the following steps: Step 1, dispersing 1.0 g MXene in a mixed solvent of 100 mL deionized water and 100 mL ethanol to form a uniform dispersion, dripping a TRIS-HCl buffer solution to adjust the pH to 8.5, then adding 0.4 g dopamine hydrochloride into the solution, and continuously reacting at room temperature for 12 h; Step 2, centrifuging 8000 rpm after the reaction is finished to collect a product, alternately washing 3 times by using deionized water and absolute ethyl alcohol, and then vacuum drying at 55 ℃ to obtain a product P@MXene; Step 3, dispersing 1.0 g of P@MXene in 100mL DMF, adding 0.6 g DOPO after ultrasonic dispersion for a period of time, heating to 60 ℃ and introducing nitrogen to protect reaction 6 h; step 4, centrifugally collecting a product 8000 rpm after the reaction is finished, washing 3 times by using absolute ethyl alcohol to remove substances which are not completely reacted, and then drying 8h in vacuum at 55 ℃ to obtain a product P@MXene-DOPO; Step 5, 1.06 g of 1,3, 5-benzene trimethyl acyl chloride is taken and dissolved in 30mL ethyl acetate to obtain a mixed solution, then 0.5 g of P@MXene-DOPO is taken and added into 10 mL ethyl acetate, ultrasonic treatment is carried out for 20 min to obtain a uniform dispersion, and then the uniform dispersion is slowly dripped into the mixed solution, and the temperature is controlled by a 0 ℃ ice bath and the stirring is kept at a low speed in the dripping process; Step 6, taking 0.32 g p-phenylenediamine and 1.42 g triethylamine and dissolving the p-phenylenediamine and the 1.42 triethylamine in 15 mL ethyl acetate to obtain a mixed solution, slowly dripping the mixed solution into the mixed solution obtained in the step 5, keeping 0 ℃ for reaction 2h after dripping, and continuously reacting at room temperature for 24 h; And 7, after the reaction is finished, adding 5mL DMF into the mixed solution, heating to 60 ℃, condensing and refluxing to react 12h, centrifuging 8000 rpm to collect products, washing 3 times with deionized water, absolute ethyl alcohol and acetone respectively, and vacuum drying at 55 ℃ to obtain the final flame retardant P@MXene-DOPO@COF-1 after the solvent is clear and colorless.
9. A composite flame retardant with modified MXene surface in-situ condensation to generate a phosphorus-containing covalent organic framework network, which is characterized by being prepared by the method of claim 1.
10. An epoxy resin composite material, which is characterized in that the epoxy resin composite material is prepared from the composite flame retardant according to claim 9, wherein the addition amount of the composite flame retardant is 2-4wt% of the total mass of the epoxy resin composite material, and the preparation method comprises the following steps: Step 1, adding a certain amount of the flame retardant and a certain amount of acetone into a flask, and keeping ultrasonic stirring; Step 2, placing epoxy resin into an oven, heating to melt, weighing a certain amount of melted epoxy resin, adding the epoxy resin into the flask, continuing ultrasonic stirring, placing the flask into an oil bath pot, heating and stirring to volatilize acetone; And 3, grinding the curing agent into fine powder, putting the fine powder into a beaker, heating to melt, adding the fine powder into the flask in the step 2, uniformly mixing, pouring the mixture into a mold, and then putting the mold into an oven to dry the mold at different temperature gradients to obtain the composite material.

Description

Preparation method of composite flame retardant for generating phosphorus-containing covalent organic framework network by in-situ condensation of modified MXene surface Technical Field The invention belongs to the technical field of flame-retardant composite materials, and particularly relates to a preparation method of a composite flame retardant for generating a phosphorus-containing covalent organic framework network by in-situ condensation of a modified MXene surface. Background Epoxy resins (EP) are typical of combustible thermosetting resins which are susceptible to rapid decomposition under the action of a fire source, produce a large amount of combustible volatiles and fumes, and are accompanied by the release of toxic gases such as CO, severely limiting their further use in the field of high safety. Therefore, the development of a flame retardant material with high efficiency, low addition and excellent smoke suppression effect becomes an important direction of the current safety protection research of epoxy resin. MXene, as a two-dimensional transition metal carbon/nitride material, has large specific surface area, excellent thermal conductivity and shielding effect, and has shown potential application value in the flame-retardant field. However, the single use of MXene has the problems of poor dispersibility, insufficient interfacial compatibility, limited thermal stability and the like, the flame retardant effect is difficult to fully exert, and meanwhile, the inhibition effect on smoke and CO still has a larger improvement space. Covalent organic framework material (COF) is used as a highly ordered porous crystal material, and a P/N synergistic flame-retardant system can be formed by introducing phosphorus-containing monomers, so that a new structural advantage is provided for condensed phase catalytic carbonization and gas phase free radical capture. However, COF materials themselves are susceptible to agglomeration and are difficult to uniformly disperse in a polymer matrix, resulting in difficulty in stable exertion of their flame retardant properties. Therefore, how to construct a novel multi-stage composite flame-retardant system with the structure stability, the interface reactivity and the high-efficiency collaborative flame-retardant capability by utilizing the two-dimensional shielding effect of MXene and the gas phase/condensed phase collaborative flame-retardant advantage of the phosphorus-containing COF is a key problem to be solved at present. Disclosure of Invention The invention provides a method for preparing a multifunctional composite flame retardant by constructing a phosphorus-containing covalent organic framework network on the surface of MXene through an in-situ condensation technology and combining a nano-composite technology. The material can obviously improve the fire safety of the epoxy resin, and simultaneously cooperatively strengthen the mechanical property of the epoxy resin, thereby providing an innovative solution for developing high-performance polymer composite materials. The invention is realized by the following technical scheme: A preparation method of a composite flame retardant for generating a phosphorus-containing covalent organic framework network by in-situ condensation of a modified MXene surface comprises the following steps: Step 1, dispersing MXene in a mixed solvent of deionized water and ethanol to form a uniform dispersion, dripping a pH regulator to regulate the solution to be alkalescent, then adding a certain amount of surface modifier into the solution, and continuously reacting for a period of time at room temperature; Step 2, centrifugally collecting a product after the reaction is finished, alternately washing the product with deionized water and absolute ethyl alcohol, and then carrying out vacuum drying to obtain a product P@MXene; step 3, dispersing P@MXene in a polar solvent, adding a certain amount of phosphorus-containing active grafting agent after ultrasonic dispersion for a period of time, heating and introducing protective gas for reaction for a period of time; Step 4, centrifugally collecting a product after the reaction is finished, washing the product with absolute ethyl alcohol to remove substances which are not completely reacted, and then drying the product in vacuum to obtain a product P@MXene-DOPO; Step 5, dissolving a certain amount of polyacyl chloride monomer in an organic solvent to obtain a mixed solution, then adding a certain amount of P@MXene-DOPO into the organic solvent, performing ultrasonic treatment to obtain a uniform dispersion, then slowly dripping the uniform dispersion into the mixed solution, and controlling the temperature of an ice bath in the dripping process; Step 6, taking a certain amount of diamine monomer and acid binding agent, dissolving the diamine monomer and the acid binding agent in an organic solvent to obtain a mixed solution, slowly adding the mixed solution into the mixed solution ob