A flame retardant with both wave absorption and smoke suppression functions and its preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2023-10-11
- Publication Date
- 2026-06-30
Smart Images
Figure CN117210018B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flame retardant technology, specifically relating to a flame retardant with both wave absorption and smoke suppression functions and its preparation method. Background Technology
[0002] The release of heat and smoke toxicity from the decomposition of the polymer matrix is considered a major factor contributing to fire hazards. Many flame retardants have been designed and have demonstrated excellent flame-retardant effects, especially in suppressing the heat of combustion. However, reports on functional fillers designed for smoke suppression properties are scarce. Therefore, more attention should be paid to designing functional flame retardants that simultaneously possess both flame-retardant and smoke-suppressing properties. Considering that smoke release during polymer combustion is mainly attributed to the incomplete combustion of pyrolyzed volatiles, and that large particles cannot be efficiently captured by microporous metal-organic frameworks (MOFs), the synthesis of hierarchically porous open nanostructured MOFs has been considered an effective way to address this issue, improving the capture capacity of MOFs for smoke particles of different sizes. To date, only a few MOF-based strategies have been reported for the preparation of hierarchically porous cages, and these strategies are mainly limited to wet chemical methods. Furthermore, with the development of 5G communication technology and the widespread application of related equipment, various electronic devices, while bringing efficiency and convenience to people's lives, also pose potential health risks. To address the increasingly serious electromagnetic pollution, there is an urgent need for high-performance microwave absorbing materials that can meet various requirements. In the future, the application of flame retardants may expand to more complex environments and fields, which requires flame retardants to have more functions to meet the growing demand. Multifunctionality is the development direction of advanced flame retardant materials in the future; however, there is currently very little research in this area.
[0003] Dai et al. (DOI:10.1016 / j.cej.2021.129697) reported a hierarchical porous organophosphorus-modified hollow bimetallic organic framework (W-Zr-MOF-DOPO) using zirconium-based MOF as a template and sodium tungstate as an etchant. The transition metal and hierarchical porosity of the prepared flame retardant effectively promote the catalytic carbonization and adsorption of pyrolysis volatiles. Only 3 wt% of W-Zr-MOF-DOPO was added to impart a limiting oxygen index of 32.2% to the epoxy composite and achieve a UL-94V-0 rating. In particular, the peak total smoke release and heat release rates of the epoxy composite were significantly reduced by 36% and 58%, respectively, compared to pure epoxy. However, this method requires a strict process, precise control of reaction conditions, and has a relatively limited functionality. Patent CN112745502A discloses a method for preparing flame-retardant and microwave-absorbing polyimide foam. This patented technology utilizes the high open-cell ratio of polyimide to fill the pores and walls of the foam with flame retardants and microwave-absorbing agents, thereby giving the foam certain microwave absorption and flame-retardant properties. However, adding flame retardants and microwave-absorbing agents separately undoubtedly increases the filler loading in the composite material, resulting in significant drawbacks in terms of the composite material's mechanical properties and cost. Therefore, synthesizing a flame retardant that combines microwave absorption and smoke suppression functions has become a highly challenging yet significant research topic. Summary of the Invention
[0004] The purpose of this invention is to solve the problems of existing flame retardants, such as single function, poor smoke suppression effect and large addition amount, and to provide a flame retardant with both wave absorption and smoke suppression functions and its preparation method.
[0005] The objective of this invention is achieved through the following technical solution.
[0006] A flame retardant with both wave absorption and smoke suppression functions is a hierarchical porous metal-organic framework material with a three-dimensional polygonal structure, a size of 1-3 μm, and a pore size distribution between 1.0 and 50.0 nm; its interior and surface carry nano-transition metal oxides, the content of which accounts for 25% to 65% of the total mass.
[0007] This invention provides a method for preparing a flame retardant that combines wave absorption and smoke suppression functions, comprising the following steps:
[0008] (S1) Add the metal-organic framework material to an organic solvent, disperse it by ultrasonication to obtain a suspension; coat the suspension onto the inner wall of a container, and dry it until the liquid phase evaporates to obtain a container A with the metal-organic framework material inside.
[0009] (S2) Fill the polytetrafluoroethylene-lined container B with an aqueous solution of etching agent;
[0010] (S3) Place the container A obtained in step (S1) into the container B obtained in step (S2), place it in an oxygen-containing atmosphere, seal it, and then place it in a reaction vessel. Place it in a forced-air oven and react under specific conditions. Stop the reaction. After cooling the reaction vessel to room temperature, open the reaction vessel and disperse the product on the inner wall of container A into an organic solvent under ultrasonic treatment. Centrifuge, wash, and dry to obtain a flame retardant with both wave absorption and smoke suppression functions. Figure 1 This is a schematic diagram of the flame retardant synthesized in this invention, which combines wave absorption and smoke suppression functions.
[0011] Further, the metal-organic framework material mentioned in step (S1) is a cobalt-based zeolite imidazole ester framework series material (ZIFs), including but not limited to ZIF-67; iron / cobalt / nickel-based Lavasil framework series materials (MILs), including but not limited to MIL-45 (Co), MIL-45 (Fe), MOF-74 (Ni) and MIL-53 (Fe).
[0012] Further, the organic solvents mentioned in steps (S1) and (S3) are selected from one or a mixture of several of methanol, ethanol, acetone, dichloromethane, tetrahydrofuran, and acetonitrile; in step (S1), the mass ratio of the metal-organic framework material to the organic solvent is 1:10-200.
[0013] Further, the etching agent in step (S1) is phytic acid, acetic acid, phosphoric acid, urea, or ammonia.
[0014] The mechanism of action of the etchant of this invention is described below:
[0015] The mechanism of phytic acid etching: Phytic acid molecules hydrolyze at high temperatures to produce phosphoinositol with 1 to 5 phosphate groups, while releasing phosphoric acid. Therefore, the formation of defects in cobalt-based zeolite imidazole ester framework materials (ZIFs) or iron / cobalt / nickel-based Lavasil framework materials (MILs) is due to the phosphoprotonation of their ligands, leading to the breakage of the original coordination bonds.
[0016] Etching mechanism of acetic acid and phosphoric acid: Acetic acid and phosphoric acid diffuse to the ligands of gas-phase protonated cobalt-based zeolite imidazole ester framework materials (ZIFs) or iron / cobalt / nickel-based Lavasil framework materials (MILs), causing the original coordination bonds to break and forming defects.
[0017] The etching mechanism of ammonia: Ammonia molecules diffuse into the gas phase and combine with metal ions of cobalt-based zeolite imidazole ester framework materials (ZIFs) or iron / cobalt / nickel-based Lavasil framework materials (MILs). Because the final products formed by the metal ions in the above materials under alkaline conditions are more thermodynamically stable than the coordination bonds between the metal ions and ligands, the original coordination bonds break, and the ligands are replaced by ammonia, forming defects.
[0018] The etching mechanism of urea: Urea decomposes at high temperature to produce ammonia and carbon dioxide. Ammonia molecules diffuse into the gas phase and combine with metal ions of cobalt-based zeolite imidazole ester framework materials (ZIFs) or iron / cobalt / nickel-based Lavasil framework materials (MILs). Because the final products formed by the metal ions in the above materials under alkaline conditions are more thermodynamically stable than the coordination bonds between metal ions and ligands, the original coordination bonds break, and the ligands are replaced by ammonia, forming defects.
[0019] The functional description of the flame retardant with both wave absorption and smoke suppression functions obtained in this invention is as follows: The instability of metal-organic frameworks (MOFs) under acidic or alkaline conditions leads to the breakage of coordination bonds between ligands and metal ions. When all the ligands around a metal ion are dissociated, it detaches from the parent framework of the MOF and further combines with oxygen in the environment. Due to the limitations of the porosity of the MOF and the amount of dissociated metal ions, nano-transition metal oxides are generated. On the one hand, the dissociation of some ligands and metal ions increases the pore size and exposed active sites of the MOF, improving its smoke capture ability and catalytic effect. On the other hand, the derived nano-transition metal oxides have magnetic properties that can mitigate magnetic loss, achieving good impedance matching with the hierarchical porous MOF.
[0020] The material and shape of the container described in step (S1) are not particularly limited. For example, beakers, conical flasks, round-bottom bottles, isotope bottles, and acid and alkali resistant containers with polytetrafluoroethylene linings can be used for a long time at high temperatures, such as 200°C.
[0021] The mass ratio of the etchant in step (S2) to the metal-organic framework material in step (S1) is 10-150:1.
[0022] The mass concentration of the etchant in the aqueous solution of the etchant in step (S2) varies depending on the etchant. Specifically, the mass concentration of phytic acid solution is 10%-70%; the mass concentration of acetic acid solution is 50%-95%; the mass concentration of phosphoric acid solution is 5%-60%; the mass concentration of ammonia is 10%-35%; and the mass concentration of urea solution is 60%-100% (100% is pure urea).
[0023] The polytetrafluoroethylene-lined container B described in step (S2) is larger in volume than the designated container described in step (S1), and can be completely placed inside container B.
[0024] In step (S3), the reaction is carried out under specific conditions in a forced-air drying oven, which is placed at 80-180°C for 4-36 hours; preferably at 110-180°C for 12-24 hours.
[0025] The oxygen-containing atmosphere mentioned in step (S3) is air, oxygen, and a mixture of oxygen and nitrogen or argon, wherein the volume concentration of oxygen is not less than 5%.
[0026] Compared with the prior art, the present invention achieves the following beneficial effects:
[0027] I. The present invention provides a flame retardant with both wave absorption and smoke suppression functions. Its initial decomposition temperature is 442℃±10℃, and its mass loss is relatively large in the temperature range of 450~700℃. At 800℃, the residue content is as high as 50% or more. It has excellent thermal stability and meets the processing requirements of flame retardants such as polyurea, epoxy resin, and polycarbonate.
[0028] II. The present invention provides a flame retardant with both wave absorption and smoke suppression functions. The material exhibits a strong polarization effect, good impedance matching and synergistic effect between the hierarchical porous structure and nano-oxides, thus demonstrating good wave absorption performance.
[0029] III. The flame retardant provided by this invention has both wave absorption and smoke suppression functions. The hierarchical porous framework structure in the components is conducive to the capture of smoke particles, and the high specific surface area exposes more active sites, which is conducive to catalyzing the char formation of the matrix, thus exhibiting excellent flame retardant and smoke suppression effects.
[0030] IV. The present invention provides a flame retardant with both wave absorption and smoke suppression functions. The preparation method adopts a vapor etching method for metal-organic frameworks. This method is carried out in an aqueous phase without the participation of organic solvents, and the etching solution can be recycled and reused. The process is green and environmentally friendly.
[0031] V. The flame retardant provided by this invention has both wave absorption and smoke suppression functions, and has multiple functional properties. The synthesis strategy and this type of multifunctional filler can provide valuable reference for the design of functional fillers and are expected to be applied to more fields. Attached Figure Description
[0032] Figure 1 This is a schematic diagram of the flame retardant synthesized in this invention, which combines wave absorption and smoke suppression functions.
[0033] Figure 2 The X-ray diffraction pattern of the flame retardant with both wave absorption and smoke suppression functions prepared in Example 1 is shown.
[0034] Figure 3 Scanning electron microscope image of the flame retardant with both wave absorption and smoke suppression functions prepared in Example 1.
[0035] Figure 4 Transmission electron microscopy image of the flame retardant with both wave absorption and smoke suppression functions prepared in Example 1.
[0036] Figure 5Thermogravimetric analysis (TGA) of the flame retardant prepared in Example 1, which combines wave absorption and smoke suppression functions.
[0037] Figure 6 The reflection loss spectrum of the flame retardant with both wave absorption and smoke suppression functions prepared in Example 1 is shown.
[0038] Figure 7 The X-ray diffraction pattern of the flame retardant with both wave absorption and smoke suppression functions prepared in Example 2 is shown.
[0039] Figure 8 Thermogravimetric analysis diagram of the flame retardant with both wave absorption and smoke suppression functions prepared in Example 2. Detailed Implementation
[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. The following embodiments are provided to better understand this invention, but do not limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.
[0041] Example 1:
[0042] (S1) Weigh 20 mg ZIF-67 and 600 mg 70% phytic acid solution at a mass ratio of 1:30. Add the weighed ZIF-67 to 2 g of methanol and sonicate for 5 min to obtain suspension A. Coat suspension A onto the inner wall of an isotope bottle and dry it in a forced-air oven at 120 °C for 12 hours to obtain a container with the inside coated with ZIF-67, denoted as container A.
[0043] (S2) Dilute the 70% phytic acid solution weighed in step (S1) with 240 mg of deionized water to obtain a 50% phytic acid solution by mass concentration, and then transfer it into a polytetrafluoroethylene liner B to obtain container B.
[0044] (S3) Place container A obtained in step (S1) into container B obtained in step (S2), cover with air, seal, and place in a reaction vessel. After sealing, place in a forced-air oven and react at 130°C for 16 hours, then stop the reaction. After cooling the reaction vessel to room temperature for 12 hours, open the reaction vessel and disperse the product in container A into methanol. Transfer to a centrifuge tube for centrifugation at 8000 rad / min for 3 minutes. Wash three times with methanol, and then place the product in a forced-air oven and dry at 80°C for 12 hours to obtain a flame retardant with both microwave absorption and smoke suppression functions. A schematic diagram of the synthesis of a flame retardant with both microwave absorption and smoke suppression functions is shown below. Figure 1 As shown.
[0045] The flame retardant prepared by the above method, which possesses both wave absorption and smoke suppression functions, has an initial decomposition temperature of 449℃, exhibits significant mass loss within the temperature range of 500–700℃, and retains 66.2% of its residue at 800℃. Its optimal reflection loss reaches -36.2dB, with an effective absorption bandwidth of 5.8GHz and a specific surface area of 1350.3m². 2 / g, with a pore size distribution between 1.2 and 46.3 nm; it is a functional flame retardant with a mesoporous ZIF-67 framework structure, carrying nano-cobalt tetroxide on its interior and surface. The obtained X-ray diffraction pattern is shown below. Figure 2 As shown. The testing instrument was a German BRUKERD8advance X-ray diffractometer. Cu-Kα radiation was selected for the test, and the test was conducted at 40 kV and 15 mA (2θ range of 2°-10°, step size 0.02°). The X-ray diffraction pattern of the flame retardant with both microwave absorption and smoke suppression functions showed characteristic peaks of ZIF-67 and cobalt tetroxide, proving that it contains ZIF-67 and cobalt tetroxide.
[0046] The flame retardant with both microwave absorption and smoke suppression functions prepared above was characterized using a scanning electron microscope (SEM). The testing instrument was a Hitachi S4800 field emission scanning electron microscope (Hitachi, Japan). The tests were conducted at an accelerating voltage of 15 kV, and the samples were sputter-coated with gold. The resulting SEM images are shown below. Figure 3 .
[0047] The flame retardant with both microwave absorption and smoke suppression functions prepared above was characterized using a transmission electron microscope (TEM). The instrument used was an HT7700 TEM (Hitachi, Germany). The sample was observed under a 120 kV electron source. The sample was prepared by dispersing it in acetone, then dropping it onto a supporting carbon film, and finally drying it in air. The obtained TEM images are shown below. Figure 4 .
[0048] The flame retardant with both microwave absorption and smoke suppression functions prepared above was characterized by thermogravimetric analysis using a TOLEDO STARe thermogravimetric analyzer from Mettler, Switzerland. 5 mg of sample was placed in a crucible, and the test conditions were: heating rate 20 °C / min, N2 atmosphere, gas flow rate 40 mL / min, and test temperature range 50–800 °C. The residual amounts of ZIF-67, cobalt tetroxide (purity: 99%), and the flame retardant with both microwave absorption and smoke suppression functions at 800 °C were 34.0%, 98.8%, and 60.2%, respectively. Furthermore, the component ratio of the flame retardant with both microwave absorption and smoke suppression functions was based on equation w. a* x+w b* (1-x)=w c It can be calculated, where w a wb w c The residual mass of sample a, sample b, and their mixture sample c under a nitrogen atmosphere at 800℃ is given. x represents the proportion of sample a in the system. Based on the above, the nano-transition metal oxides account for 40.4% of the total system mass. The obtained thermogravimetric curve is shown below. Figure 5 .
[0049] The flame retardant with both microwave absorption and smoke suppression functions prepared above was characterized using a vector network analyzer (Tektronix RSA600, China). The coaxial method was employed, with a sample thickness of 2.5 mm and a functional filler content of 30 wt%. Data were analyzed using MASC 2.0.0. The material exhibited an optimal reflection loss of -36.2 dB and an effective absorption bandwidth of 5.8 GHz, demonstrating excellent microwave absorption performance. The obtained reflection loss curve is shown below. Figure 6 As shown.
[0050] The flame retardant in this embodiment was applied to bisphenol A type epoxy resin (E-44), with 4,4′-diaminodiphenylmethane as a curing agent, to prepare a flame-retardant epoxy resin. When the amount of flame retardant added was 2wt%, the limiting oxygen index reached 31.3%, the vertical burning rating reached UL-94V-1, and the peak heat release rate, total heat release, and total smoke emission decreased by 33.8%, 22.3%, and 45.9% respectively compared to pure epoxy resin, meeting the application requirements of industrial flame-retardant epoxy resins.
[0051] Example 2:
[0052] (S1) Weigh 50mg ZIF-67 and 500mg phosphoric acid at a mass ratio of 1:10. Add the weighed ZIF-67 to 1g of ethanol and sonicate for 5min to obtain suspension A. Coat suspension A onto the inner wall of an isotope bottle and dry it in a forced-air oven at 120℃ for 12 hours to obtain a container with the inside coated with ZIF-67, denoted as container A.
[0053] (S2) Dilute the phosphoric acid weighed in step (S1) with 1167 mg of deionized water to obtain a phosphoric acid solution with a mass concentration of 30%, and then transfer it into a polytetrafluoroethylene liner B to obtain container B.
[0054] (S3) Place container A obtained in step (S1) into container B obtained in step (S2), cover with air, seal and place in a reaction vessel. After sealing, place in a forced-air oven and react at 150°C for 15 hours, then stop the reaction. After cooling the reaction vessel to room temperature for 12 hours, open the reaction vessel, disperse the product in container A into ethanol, transfer to a centrifuge tube for centrifugation, centrifuge at 8000 rad / min for 3 minutes, wash 3 times with ethanol, and then place the product in a forced-air oven and dry at 80°C for 12 hours to obtain a flame retardant with both microwave absorption and smoke suppression functions.
[0055] The resulting flame retardant, possessing both wave absorption and smoke suppression functions, has an initial decomposition temperature of 452℃, exhibits significant mass loss within the temperature range of 480–680℃, and retains 68.4% of its residue at 800℃. It achieves an optimal reflection loss of -33.1dB, an effective absorption bandwidth of 6.2GHz, and a specific surface area of 1430.5m². 2 / g, with a pore size distribution between 2.2 and 45.1 nm; it is a functional flame retardant with a mesoporous ZIF-67 framework structure and nano-cobalt tetroxide carried inside and on the surface.
[0056] The flame retardant prepared above, possessing both microwave absorption and smoke suppression functions, was characterized using an X-ray diffractometer. The instrument used was a German BRUKERD8 advance X-ray diffractometer, with Cu-Kα radiation selected for testing at 40 kV and 15 mA (2θ range of 2°–10°, step size 0.02°). The obtained X-ray powder diffraction pattern is shown below. Figure 7 .
[0057] The flame retardant with both microwave absorption and smoke suppression functions prepared above was characterized using a thermogravimetric analyzer. A TOLEDO STARe thermogravimetric analyzer from Mettler, Switzerland was used. 6 mg of sample was placed in a crucible, and the test conditions were: heating rate 20 °C / min, N2 atmosphere, gas flow rate 40 mL / min, and a test temperature range of 30–900 °C. The obtained thermogravimetric spectra are shown below. Figure 8 .
[0058] The flame retardant in this embodiment was applied to polyurea to prepare a flame-retardant polyurea composite material. When the amount of flame retardant added was 6 wt%, the limiting oxygen index reached 23.3%, the vertical burning rating reached UL-94V-1, and the peak heat release rate, total heat release, and total smoke release were reduced by 35.8%, 23.9%, and 46.6% respectively compared to pure polyurea, meeting the application requirements of industrial flame-retardant polyurea.
[0059] Example 3:
[0060] (S1) Weigh 50 mg of MOF-74(Ni) and 5 g of urea at a mass ratio of 1:100. Add the weighed MOF-74(Ni) to 1.5 g of acetonitrile and sonicate for 5 min to obtain suspension A. Coat suspension A onto the inner wall of an isotope bottle and dry it in a forced-air oven at 120 °C for 12 hours to obtain a container with the inside coated with MOF-74(Ni), denoted as container A.
[0061] (S2) Dilute the urea weighed in step (S1) with 1.25g of deionized water to obtain a urea solution with a mass concentration of 80%, and then transfer it into a polytetrafluoroethylene liner B to obtain container B.
[0062] (S3) Place container A obtained in step (S1) into container B obtained in step (S2), introduce a mixture of oxygen and nitrogen (21% oxygen and 79% nitrogen), cover and place in a reaction vessel. After sealing, place in a forced-air drying oven at 180°C for 12 hours, then stop the reaction. After cooling the reaction vessel to room temperature for 12 hours, open the reaction vessel, disperse the product in container A into acetonitrile, transfer to a centrifuge tube for centrifugation, centrifuge at 9000 rad / min for 5 minutes, wash with acetonitrile 4 times, and then place the product in a forced-air drying oven at 80°C for 12 hours to obtain a flame retardant with both wave absorption and smoke suppression functions.
[0063] The resulting flame retardant, possessing both wave absorption and smoke suppression functions, has an initial decomposition temperature of 440℃, exhibits significant mass loss within the 500–700℃ temperature range, and retains 56.8% of its residue at 800℃. It achieves an optimal reflection loss of -29.8dB, an effective absorption bandwidth of 5.2GHz, and a specific surface area of 1165.8m². 2 / g, with a pore size distribution between 2.3 and 38.1 nm; it is a functional flame retardant with a mesoporous MOF-74(Ni) framework structure and nano-nickel oxide carried inside and on the surface.
[0064] The flame retardant in this embodiment was applied to polycarbonate to prepare a flame-retardant polycarbonate composite material. When the amount of flame retardant added was 5 wt%, the limiting oxygen index reached 26.4%, the vertical burning rating reached UL-94V-1, and the peak heat release rate, total heat release, and total smoke release were reduced by 38.8%, 25.6%, and 48.2% respectively compared to pure polycarbonate, meeting the application requirements of industrial flame-retardant polycarbonate.
[0065] Example 4:
[0066] (S1) Weigh 100mg of MIL-45(Fe) and 6g of acetic acid at a mass ratio of 1:60. Add the weighed MIL-45(Fe) to 5g of acetone and sonicate for 10min to obtain suspension A. Coat suspension A onto the inner wall of an isotope bottle and dry it in a forced-air oven at 120℃ for 12 hours to obtain a container with the inside coated with MIL-45(Fe), denoted as container A.
[0067] (S2) Dilute the acetic acid weighed in step (S1) with 4g of deionized water to obtain an acetic acid solution with a mass concentration of 60%, and then transfer it into a polytetrafluoroethylene liner B to obtain container B.
[0068] (S3) Place container A obtained in step (S1) into container B obtained in step (S2), cover with an oxygen atmosphere, and place in a reaction vessel. After sealing, place in a forced-air drying oven at 110°C for 24 hours, then stop the reaction. After cooling the reaction vessel to room temperature for 12 hours, open the reaction vessel, disperse the product in container A into acetone, transfer to a centrifuge tube for centrifugation, centrifuge at 9000 rad / min for 4 minutes, wash with acetone 4 times, and then place the product in a forced-air drying oven at 110°C for 12 hours to obtain a flame retardant with both wave absorption and smoke suppression functions.
[0069] The resulting flame retardant, possessing both wave absorption and smoke suppression functions, has an initial decomposition temperature of 438℃, exhibits significant mass loss within the 500–700℃ temperature range, and retains 53.6% of its residue at 800℃. It achieves an optimal reflection loss of -37.2dB, an effective absorption bandwidth of 6.8GHz, and a specific surface area of 1480.1m². 2 / g, with a pore size distribution between 1.8 and 36.3 nm; it is a functional flame retardant with a mesoporous MIL-45(Fe) framework structure and nano-Fe3O4 carried on its interior and surface.
[0070] The flame retardant in this embodiment was applied to polyurea to prepare a flame-retardant polyurea composite material. When the amount of flame retardant added was 5 wt%, the limiting oxygen index reached 21.4%, and the peak heat release rate, total heat release, and total smoke release decreased by 30.8%, 19.8%, and 40.2% respectively compared to pure polyurea, meeting the application requirements of industrial flame-retardant polyurea.
Claims
1. A flame retardant with both wave-absorbing and smoke-suppressing functions, characterized in that, The flame retardant is a hierarchical porous metal-organic framework material with a size of 1-3 μm and a pore size distribution between 1.0 and 50.0 nm; its interior and surface carry nano-transition metal oxides, wherein the content of nano-transition metal oxides accounts for 25% to 65% of the total mass; The flame retardant, which combines wave absorption and smoke suppression functions, is prepared by a method including the following steps: (S1) Add the metal-organic framework material to an organic solvent, disperse it by ultrasonication to obtain a suspension; coat the suspension onto the inner wall of a container, and dry it until the liquid phase evaporates to obtain a container A with the metal-organic framework material inside. (S2) Fill the polytetrafluoroethylene-lined container B with an aqueous solution of an etchant; the etchant is phytic acid, acetic acid, phosphoric acid or urea; the mass ratio of the etchant in step (S2) to the metal-organic framework material in step (S1) is 10-150:1; (S3) Place container A obtained in step (S1) into container B obtained in step (S2), place it in an oxygen-containing atmosphere, seal container B and place it in a reaction vessel, place it in a forced-air oven for reaction, and stop the reaction; after cooling the reaction vessel to room temperature, open the reaction vessel, disperse the product on the inner wall of container A into an organic solvent under ultrasonic treatment, centrifuge, wash and dry to obtain a flame retardant with both wave absorption and smoke suppression functions.
2. The flame retardant with both wave absorption and smoke suppression functions according to claim 1, characterized in that, The metal-organic framework material mentioned in step (S1) is a cobalt-based zeolite imidazole ester framework material or a Lavasil framework material.
3. The flame retardant with both wave absorption and smoke suppression functions according to claim 2, characterized in that, The cobalt-based zeolite imidazole ester framework material is ZIF-67; the Lavasil framework material is selected from at least one of MIL-45(Co), MIL-45(Fe) and MIL-53(Fe).
4. The flame retardant with both wave absorption and smoke suppression functions according to claim 1, characterized in that, The organic solvents used in steps (S1) and (S3) are selected from one or a mixture of several of methanol, ethanol, acetone, dichloromethane, tetrahydrofuran, and acetonitrile; in step (S1), the mass ratio of the metal-organic framework material to the organic solvent is 1:10-200.
5. The flame retardant with both wave absorption and smoke suppression functions according to claim 1, characterized in that, The mass concentration of the etchant in the aqueous solution of the etchant in step (S2) varies depending on the etchant. The mass concentration of phytic acid solution is 10%-70%; the mass concentration of acetic acid solution is 50%-95%; the mass concentration of phosphoric acid solution is 5%-60%; and the mass concentration of urea solution is 60%-80%.
6. The flame retardant with both wave absorption and smoke suppression functions according to claim 1, characterized in that, In step (S3), the reaction is carried out in a forced-air oven at 80~180℃ for 4-36 hours.
7. The flame retardant with both wave absorption and smoke suppression functions according to claim 6, characterized in that, In step (S3), the reaction is carried out in a forced-air oven at 110-180°C for 12-24 hours.
8. The flame retardant with both wave absorption and smoke suppression functions according to claim 1, characterized in that, The oxygen-containing atmosphere mentioned in step (S3) is air, oxygen, a mixture of oxygen and nitrogen, or a mixture of oxygen and argon, wherein the volume concentration of oxygen is not less than 5%.