A method for preparing a bimetallic MOF organic fiber-based fireproof coating

Abstract

The application discloses a preparation method of a bimetallic MOF organic fiber-based fireproof coating, and the preparation steps are as follows: (1) preparation of an ORF@Co, Zn-MOF@Si composite flame retardant; (2) preparation of the bimetallic MOF organic fiber-based fireproof coating; the Co / Zn-MOF is loaded on the surface of seaweed fiber (ORF) through a coprecipitation method, and a layer of organosilicon is loaded on the surface of the seaweed fiber, so that the ORF@Co, Zn-MOF@Si composite flame retardant is obtained; then, the ORF@Co, Zn-MOF@Si composite flame retardant is added into an epoxy resin matrix, and a super-thin epoxy intumescent fireproof coating with good fireproof performance and smoke suppression effect is successfully prepared; the coating is characterized in that the catalytic carbonization effect of the bimetallic material can promote the high-temperature setting carbonization of the seaweed acid fiber, and in addition, the introduction of the organosilicon into the resin produces a stable silicon network in the combustion process, and the silicon network plays a role in reinforcing the carbon layer.

Description

Technical Field

[0001] This invention belongs to the field of preparation of water-based ultrathin epoxy intumescent fire-retardant coatings, specifically relating to a method for preparing a bimetallic MOF organic fiber-based fire-retardant coating. Background Technology

[0002] Steel structures possess advantages such as high strength, light weight, fast construction speed, and high degree of industrialization, and are widely used in various fields. However, compared with reinforced concrete buildings, steel structures have poor fire resistance; when the temperature reaches 600℃, they lose strength and are prone to collapse, causing casualties and property damage. Intumescent fire-retardant materials are widely used to improve the fire resistance of steel due to their ease of construction, light weight, and effective protection of steel structures. However, the char layer of intumescent fire-retardant coatings has low strength after combustion, is prone to cracking, and has limited heat insulation capacity, preventing it from achieving the desired effect. Organic fibers, as a widely used reinforcing material, can effectively improve the strength and toughness of coatings. Compared with inorganic fibers, organic fibers can overcome the disadvantage of poor compatibility between inorganic fibers and resin matrices. Algae fiber (ORF), a naturally occurring polysaccharide organic fiber, is rich in carboxyl and hydroxyl groups on its surface. During combustion... It can release a large amount of water and carbon dioxide, effectively diluting the concentration of combustible gases, carrying away heat from the combustion zone, and reducing the temperature of the material surface; therefore, alginate fiber can be used as an effective reinforcing material to improve the flame retardant properties of polymers; however, in the field of fireproof coatings, research on organic fibers as fillers is very limited, mainly because organic fibers tend to generate amorphous carbon during combustion, which has almost no reinforcing effect on the carbon layer, and easily generates carbon monoxide (CO) gas under incomplete combustion conditions; with the development of multidisciplinary integration technology, new ideas have been provided for solving the scientific problems of carbon layer stability, carbon layer heat insulation, and organic fiber styling carbonization after the bottleneck of water-based expansion coating technology; transition metal catalysis provides technical support for the styling carbonization of organic fibers in aerobic open systems, and the styling carbonization of organic fibers provides the possibility of strengthening carbon layer stability and reducing carbon layer heat transfer efficiency. Summary of the Invention

[0003] Metal-organic frameworks (MOFs) are novel functional materials assembled through ligand bonding, using metal ions or metal clusters as nodes and multifunctional organic ligands as linkers. Due to their large specific surface area and porous structure, they can serve as effective oxygen barrier materials, absorbing and storing large amounts of smoke and harmful substances at fire scenes, and are therefore considered highly efficient organic-inorganic flame retardants. This invention first loads Co / Zn-MOF onto the surface of seaweed fiber (ORF) using a co-precipitation method, and then loads an organosilicon layer onto its surface to obtain a novel ORF@Co... Zn-MOF@Si composite flame retardant; then, a novel ORF@Co,Zn-MOF@Si composite flame retardant was added to the epoxy resin matrix to successfully prepare an ultra-thin epoxy intumescent fire retardant coating with good fire resistance and smoke suppression effect; among them, Co / Zn-MOF can not only effectively improve the char formation efficiency of the coating matrix at high temperature, but also, due to the presence of Co and Zn ions, can maintain the fibrous morphology of alginate as much as possible at high temperature, thereby playing a role in reinforcing the char layer; the introduction of organosilicon enables the composite coating to generate a large number of highly stable silicon-containing networks during combustion, thereby effectively slowing down heat transfer.

[0004] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problems is as follows.

[0005] A method for preparing a bimetallic MOF organic fiber-based fire-retardant coating includes the following steps.

[0006] 1. Preparation of ORF@Co,Zn-MOF@Si composite flame retardant.

[0007] (1) Preparation of ORF@Co,Zn-MOF hybrid: Algae fiber was dispersed in methanol and ultrasonically treated with a probe for 30 minutes to obtain an algae fiber suspension; then, zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)3·6H2O) were added to the algae fiber suspension and stirred for 60 minutes to form a brown suspension a; then, 2-methylimidazole was dissolved in 30 mL of methanol to form a transparent solution b; solution b was slowly added to suspension a and magnetically stirred for 30 minutes; the mixture of a and b was allowed to stand at room temperature for 16 hours, washed three times by centrifugation with ethanol, and dried in a vacuum oven at 40 °C to obtain ORF@Co,Zn-MOF hybrid.

[0008] (2) Preparation of ORF@Co,Zn-MOF@Si composite flame retardant: Hexadecyltrimethylammonium bromide (CTAB) was dissolved in a mixture of ethanol and water, and ORF@Co,Zn-MOF hybrid was added to the mixture. After ultrasonic dispersion for 10 minutes, tetraethyl orthosilicate (TEOS) was slowly added to the mixture and stirred for 30 minutes. After stirring for 30 minutes, ammonia water was slowly added to the mixture, and the reaction mixture was stirred again for 10 hours. Finally, the mixture was washed three times with ethanol by centrifugation, and freeze-dried to obtain the ORF@Co,Zn-MOF@Si composite flame retardant. The specific preparation diagram is shown below. Figure 1 As shown.

[0009] 2. Preparation of bimetallic MOF organic fiber-based fire-retardant coating.

[0010] Disperse appropriate amounts of melamine (MEL), pentaerythritol (PER), and ammonium polyphosphate (APP) in an appropriate amount of water and stir vigorously until a uniform expansion system suspension is obtained. Then, mix and stir the aqueous dispersion of ORF@Co,Zn-MOF@Si composite flame retardant, waterborne epoxy resin emulsion (EP), and curing agent for 10 minutes, and pour the mixture into the expansion system suspension at once to obtain a bimetallic MOF organic fiber-based fire retardant slurry. Finally, uniformly coat the bimetallic MOF organic fiber-based fire retardant slurry onto a steel plate with a sandblasting grade of Sa2. After brushing, cure at room temperature for 7 days and bake at 40℃ for 3 days to obtain a bimetallic MOF organic fiber-based fire retardant coating.

[0011] Furthermore, in step 1(1), the mass volume concentration of seaweed fiber is 0.001-0.002 g / mL.

[0012] Furthermore, in step 1(1), the mass ratio of seaweed fiber to zinc nitrate hexahydrate is 1:15-30.

[0013] Furthermore, in step 1(1), the molar ratio of zinc nitrate hexahydrate to cobalt nitrate hexahydrate is 1:1.5-2.5.

[0014] Furthermore, in step 1(1), the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:4-8.

[0015] Furthermore, in step 1(2), the mass-volume concentration of hexadecyltrimethylammonium bromide is 0.003-0.005 g / mL.

[0016] Furthermore, in step 1(2), the volume ratio of water to ethanol is 1:1-3.

[0017] Furthermore, in step 1(2), the mass ratio of ORF@Co,Zn-MOF hybrid to hexadecyltrimethylammonium bromide is 1:3-5.

[0018] Furthermore, in step 1(2), the mass-to-volume ratio (g / mL) of hexadecyltrimethylammonium bromide and tetraethyl orthosilicate is 4:3-5.

[0019] Furthermore, in step 1(2), the mass-to-volume ratio (g / mL) of hexadecyltrimethylammonium bromide and ammonia is 1:2-3.

[0020] Furthermore, in step 2, the mass ratio of polyphosphate, dipentaerythritol, and melamine is 5.5-6.5:2.5-3.5:1-1.5.

[0021] Furthermore, in step 2, the mass ratio of epoxy resin to the expansion system is 1:1-1.2.

[0022] Furthermore, in step 2, the mass ratio of epoxy resin to curing agent is 2:1-1.2.

[0023] Furthermore, the curing agent in step 2 is ethylenediamine, diethylenetriamine, or triethylenetetramine.

[0024] Furthermore, in step 2, the ORF@Co,Zn-MOF@Si composite flame retardant accounts for 2.0-5.0% of the total mass of the matrix coating system and the ORF@Co,Zn-MOF@Si composite flame retardant.

[0025] The present invention provides a method for preparing a bimetallic MOF organic fiber-based fire-retardant coating, which has the following beneficial effects.

[0026] (1) The metal oxides generated by MOF decomposition are used to simultaneously catalyze the shaping and carbonization of seaweed fibers to form a carbon skeleton, thereby further improving the conversion rate of residual carbon and inhibiting the generation of toxic gases.

[0027] (2) In the early stage of a fire, the ORF@Co,Zn-MOF@Si composite flame retardant acts as a spacer, making the heat penetration path serrated and slowing down the combustion of the polymer matrix.

[0028] (3) During the middle stage of a fire, the CO2 and H2O generated by the ORF can effectively reduce the heat and oxygen concentration in the surrounding environment, thus playing a role in gas phase flame retardancy. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the preparation process of ORF@Co,Zn-MOF@Si composite flame retardant.

[0030] Figure 2 The FT-IR spectra of ORF, Co,Zn-MOF, ORF@Co,Zn-MOF and ORF@Co,Zn-MOF@Si are shown.

[0031] Figure 3 The XRD patterns are for ORF, Co,Zn-MOF, ORF@Co,Zn-MOF, and ORF@Co,Zn-MOF@Si.

[0032] Figure 4 SEM images and EDS images of ORF@Co,Zn-MOF@Si for different samples are shown, including SEM images of (a,d)ORF, (b,e)Co,Zn-MOF and (c,f)ORF@Co,Zn-MOF@Si and EDS distribution of O, N, Co, Zn and Si elements in (g)ORF@Co,Zn-MOF@Si.

[0033] Figure 5 XPS spectrum of ORF@Co,Zn-MOF@Si composite flame retardant.

[0034] Figure 6 This is a graph showing the temperature change on the back side of the steel sheet and the coated sample.

[0035] Figure 7 Photographs of different samples after combustion, including (a) EP, (b) Co,Zn-MOF / EP, (c) ORF / EP, (d) ORF@Co,Zn-MOF / EP and (e) ORF@Co,Zn-MOF@Si / EP.

[0036] Figure 8 The expansion height and expansion rate of different samples.

[0037] Figure 9 (a) Absorbance curves and (b) Smoke density ratios for different samples.

[0038] Figure 10 The images show the XRD patterns of the carbon layers after combustion of different coatings. Detailed Implementation

[0039] Example 1.

[0040] A method for preparing a bimetallic MOF organic fiber-based fire-retardant coating includes the following steps.

[0041] 1. Preparation of ORF@Co,Zn-MOF@Si composite flame retardant.

[0042] (1) Preparation of ORF@Co,Zn-MOF hybrid: 0.15g of seaweed fiber was dispersed in 150mL of methanol and ultrasonically treated with a probe for 30 minutes to obtain seaweed fiber suspension; then, 3g of Zn(NO3)2·6H2O and 5.82g of Co(NO3)3·6H2O were added to the seaweed fiber suspension and stirred for 60 minutes to form brown suspension a; then, 5.9g of 2-methylimidazole was dissolved in 30mL of methanol to form transparent solution b; solution b was slowly added to suspension a and magnetically stirred for 30 minutes; the mixture of a and b was allowed to stand at room temperature for 16 hours, washed three times by centrifugation with ethanol, and dried in a vacuum oven at 40℃ to obtain ORF@Co,Zn-MOF hybrid.

[0043] (2) Preparation of ORF@Co,Zn-MOF@Si composite flame retardant: 0.4 g of hexadecyltrimethylammonium bromide (CTAB) was dissolved in a mixture of 50 mL of ethanol and 50 mL of water, and 0.1 g of ORF@Co,Zn-MOF hybrid was added to the mixture. After ultrasonic dispersion for 10 minutes, 0.3 mL of tetraethyl orthosilicate (TEOS) was slowly added to the mixture and stirred for 30 minutes. After stirring for 30 minutes, 0.8 mL of ammonia water was slowly added to the mixture, and the reaction mixture was stirred again for 10 hours. Finally, the mixture was washed three times by centrifugation with ethanol and freeze-dried to obtain ORF@Co,Zn-MOF@Si composite flame retardant.

[0044] 2. Preparation of bimetallic MOF organic fiber-based fire-retardant coating.

[0045] A suitable amount of melamine (MEL), pentaerythritol (PER), and ammonium polyphosphate (APP) were dispersed in a suitable amount of water and stirred vigorously until a uniform intumescent suspension was obtained. Then, the aqueous dispersion of ORF@Co,Zn-MOF@Si composite flame retardant, waterborne epoxy resin emulsion, and curing agent were mixed and stirred for 10 minutes and then poured into the intumescent suspension at one time to obtain a bimetallic MOF organic fiber-based fire retardant slurry. Finally, the bimetallic MOF organic fiber-based fire retardant slurry was uniformly coated on a steel plate with a sandblasting grade of Sa2. After brushing, it was cured at room temperature for 7 days and baked at 40℃ for 3 days to obtain a bimetallic MOF organic fiber-based fire retardant coating. The composition of different intumescent fire retardant coatings is shown in Table 1.

[0046] Table 1 Composition of different intumescent fire-retardant coatings

[0047]

[0048] Experimental Example 1.

[0049] This experimental example demonstrates the experimental analysis results related to the preparation method of a bimetallic MOF organic fiber-based fire-retardant coating.

[0050] 2.0 wt.% of ORF, Co,Zn-MOF, ORF@Co,Zn-MOF, and ORF@Co,Zn-MOF@Si hybrids were uniformly mixed with waterborne epoxy resin, curing agent, and expansion system suspension to prepare 2.0 wt.% ORF / EP, Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP, and ORF@Co,Zn-MOF@Si / EP coatings, respectively. Then, the uniformly dispersed coatings were brushed onto the surface of steel sheets with a pretreatment grade of Sa2. After brushing, the coatings were cured at room temperature for 7 days and baked at 40℃ for 3 days to obtain the sample coatings. In addition, pure EP coatings were used as controls in the experiment.

[0051] (1) The FT-IR spectra of ORF, Co,Zn-MOF, ORF@Co,Zn-MOF and ORF@Co,Zn-MOF@Si are as follows: Figure 2 As shown; for Co,Zn-MOF, 1308-1177 cm⁻¹ -1 The vibration peaks within the range are attributed to the bending vibrations of C=C and CO, while the 761cm peak is attributed to these vibrations. -1 693cm -1 The fluctuation peaks can be attributed to bending vibrations between CHs; for the ORF, they can be observed at 3463 cm⁻¹. -1 (stretching vibration of -OH), 2854 and 2927 cm⁻¹ -1 (stretching oscillation of CH), 1720cm -1 (Absorption peak of C=O vibration in carboxylic acids), 1640 cm⁻¹ -1 (bending vibration of NH) and 1453cm -1 Relevant characteristic peaks were observed at (asymmetric and symmetric stretching vibrations of the COOH group); characteristic peaks of ORF and Co,Zn MOF were clearly seen on the FT-IR curve of the ORF@Co,Zn-MOF hybrid, proving that Co,Zn-MOF has been successfully loaded onto ORF; for the ORF@Co,Zn-MOF@Si hybrid, the characteristic peaks are located at 1250 cm⁻¹. -1 1140cm -1 The nearby wave peaks are mainly attributed to the stretching vibrations of the C-C bonds, while those located at 1094 cm⁻¹ are... -1 950cm -1 The fluctuation peak is attributed to the characteristic peak of Si-O stretching; at 425 cm⁻¹ -1 There is an absorption peak nearby, which is related to the tensile vibration of metal-N in the material. The experimental results show that TEOS has been successfully loaded onto the surface of ORF@Co,Zn-MOF hybrid.

[0052] (2) The XRD patterns of ORF, Co,Zn-MOF, ORF@Co,Zn-MOF and ORF@Co,Zn-MOF@Si are as follows: Figure 3 As shown, the peaks at 7.3°, 10.4°, 12.6°, 16.3°, 17.9°, 24.4° and 26.7° belong to the (110), (101), (112), (330), (002), (111) and (221) crystal planes of Co,Zn-MOF, respectively; the characteristic peaks at 17.3° and 29.8° are attributed to ORF; the ORF@Co,Zn-MOF and ORF@Co,Zn-MOF@Si hybrids retain the characteristic peaks of both Co,Zn-MOF and ORF, which proves that the crystal structure of the constituent materials remains unchanged in the composite material.

[0053] (3) The microstructures of ORF, Co,Zn-MOF, ORF@Co,Zn-MOF, and ORF@Co,Zn-MOF@Si were characterized by SEM, such as... Figure 4 As shown; from Figure 4 As can be seen in (a,d), the original ORF exhibits a smooth surface structure; Figure 4 In (b,e), the rod-like structure of the ORF remains unchanged, and the surface is loaded with regular and uniform polyhedral particles, which proves the successful loading of Co,Zn-MOF; for ORF@Co,Zn-MOF@Si( Figure 4 Samples (c,f) show an organic film covering the surface, demonstrating the successful loading of TEOS onto the ORF@Co,Zn-MOF surface. Furthermore... Figure 4 (g) Surface scanning can detect O, N, Co, Zn and Si elements, which further proves that Co,Zn-MOF and TEOS have been successfully loaded onto ORF.

[0054] (4) XPS spectra of ORF@Co,Zn-MOF@Si are as follows Figure 5 As shown; from Figure 5 (a) clearly shows that the ORF@Co,Zn-MOF@Si hybrid material contains C, N, O, Zn, Co, and Si elements, revealing the material's composition and confirming the successful doping of Co,Zn-MOF and TEOS; Figure 5 In (b), the C1S spectrum decomposes into four peaks at 284.3 eV, 284.8 eV, 286.0 eV, and 288.3 eV, which are attributed to the signals of the CC / CH, C=C, CN / CO, and O=CO bonds, respectively; in the N1S spectrum ( Figure 5 (c) The three signal peaks at 398.8 eV, 400.2 eV, and 401.7 eV originate from =N-, NH, and CN bonds, respectively; Figure 5In (d), the O1S spectrum mainly consists of CO (530.8 eV), -OH (531.6 eV), CO-Si (532.6 eV), and Si-O-Si (533.2 eV); in the Co2p spectrum ( Figure 5 (e) mainly shows the characteristic peaks of Co2p3 / 2 (781.1 eV) and Co2p1 / 2 (797.1 eV); in Figure 5 In (f), the Zn2p spectrum can detect two peaks belonging to Zn2p3 / 2 (1021.6 eV) and Zn2p1 / 2 (1044.62 eV); for the Si2p spectrum ( Figure 5 (g)), the peak values ​​at 102.5 eV and 103.4 eV belong to Si-O-Si and Si-O- bonds, respectively.

[0055] (5) The trend of back surface temperature change during combustion of pure EP, ORF / EP, Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP and ORF@Co,Zn-MOF@Si / EP is as follows: Figure 6 As shown; from Figure 6 It is clearly evident that the uncoated steel plate heats up rapidly within 10 minutes, a temperature rise that severely impacts its lifespan and leads to a decline in its performance. After applying the EP coating, the temperature on the back of the steel plate is significantly lower than that of the pure steel plate, eventually stabilizing at 268.1℃, demonstrating that adding EP effectively insulates the steel plate. After adding ORF, the final temperature of the ORF / EP coating remains at 215.1℃, 53℃ lower than EP, proving that the introduction of ORF greatly improves the thermal insulation performance of the intumescent coating. After coating with Co,Zn-MOF / EP, the final temperature on the back of the sample remains at 191.6℃, attributed to the MOF absorbing a large amount of heat from the surrounding area during combustion. The catalytic carbonization ability of oxygen, cobalt ions, and zinc ions was observed. For the ORF@Co,Zn-MOF / EP sample, the temperature on the back side of the steel plate remained stable at 178.5℃, indicating that Co,Zn-MOF successfully catalyzed the directional carbonization of ORF during combustion, enhancing the carbon layer strength, improving thermal insulation, and playing a positive role in hindering heat transfer. The ORF@Co,Zn-MOF@Si / EP sample had the lowest back side temperature at 166.4℃. The main reason for this is that, in addition to the catalytic effect of Co,Zn-MOF on ORF, the SiO2 core-shell structure retained after the decomposition of Co,Zn-MOF also has a synergistic flame-retardant effect that supports the stability of the carbon layer.

[0056] (6) Figure 7Macroscopic photographs of EP, ORF / EP, Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP, and ORF@Co,Zn-MOF@Si / EP after combustion are shown. The images reveal different surface states of the different samples after combustion; pure EP ( Figure 7 (a) shows that after combustion, the middle part peels off, and large pores are present around it. This indicates that its carbon layer strength is low, causing the steel to be directly exposed to flame conditions, thereby increasing the heat transfer efficiency and greatly reducing the heat insulation effect; for the Co,Zn-MOF / EP sample ( Figure 7 (b) The significant improvement in carbon layer detachment after combustion indicates that the addition of Co,Zn-MOF enhances the strength of the carbon layer, effectively slows down heat transfer, and significantly improves the protective effect on the steel; Figure 7 In (c), cracks still existed on the surface of the char layer after the ORF / EP composite coating burned, but unlike the EP coating, the char layer did not peel off. This is because the compatibility of the hydroxyl and carboxyl groups on the surface of the seaweed fiber with the water-based epoxy resin increased the densification of the char layer; from Figure 7 (d) It can be seen that only a few fine cracks appeared in ORF@Co,Zn-MOF / EP, which is attributed to the catalytic carbonization ability of Co,Zn-MOF on ORF; for ORF@Co,Zn-MOF@Si / EP samples ( Figure 7 (e) The carbon layer surface has no obvious defects such as pores and cracks, which has a positive effect on its excellent thermal insulation performance.

[0057] (7) The expansion parameters obtained from the experiment are as follows: Figure 8As shown in the figure, the expansion height of pure EP is 10.5 mm and the expansion rate is 4.3, indicating a poor expansion effect and limited protection for the steel plate. After adding Co,Zn-MOF filler, the swelling height and expansion rate are 16.3 mm and 8.63, respectively, due to the formation of bimetallic catalytic carbon in the filler. However, the swelling height is uneven, which may be due to the uneven dispersion of the filler in the epoxy resin. For the ORF / EP sample, the highest expansion height and expansion rate of the carbon layer are 19.8 mm and 11.4 mm, respectively, demonstrating that ORF can effectively limit gas overflow during combustion, thereby improving the expansion rate of the carbon layer. For ORF@ The Co,Zn-MOF / EP sample exhibited an expansion height of 21.5 mm and an expansion rate of 12.6%, primarily attributed to the catalytic effect of Co,Zn-MOF on the char formation ability of ORF, converting amorphous carbon produced by ORF into fixed carbon during combustion, thereby increasing the expansion height of the char layer. As for the ORF@Co,Zn-MOF@Si / EP sample, it achieved the maximum expansion height (24.6 mm) and maximum expansion rate (15.2%), attributable to the synergistic effect between components and the introduction of Si elements during combustion, which, together with the decomposition products of Co,Zn-MOF, formed a hollow structure, providing excellent support for the char layer.

[0058] (8) The properties of the smoke generated during the combustion of EP, ORF / EP, Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP and ORF@Co,Zn-MOF@Si / EP were tested, and the results are as follows: Figure 9 As shown; from Figure 9 (a) It can be seen that, throughout the entire process, the light absorption rate of pure EP is greater than that of other composite coatings, which proves the effective role of ORF and its hybrids in suppressing smoke in EP; from Figure 9(b) It can be seen that the smoke density grades of EP, ORF / EP, Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP, and ORF@Co,Zn-MOF@Si / EP are 61.9%, 56.7%, 51.6%, 45.8%, and 41.2%, respectively. The decrease in smoke density grade of the ORF / EP coating is mainly attributed to the inert gases (such as water and carbon dioxide) generated by the ORF at high temperatures, which act as gas-phase flame retardants; while the smoke density grade of Co,Zn-MOF / EP... The lower smoke density level is attributed to the fact that Co / Zn oxide catalyzes the cross-linking of more small molecules into carbon, thereby reducing the formation of volatiles. At the same time, the mesoporous structure of MOF has a certain smoke adsorption capacity. The further reduction in smoke density level of ORF@Co,Zn-MOF / EP is attributed to the synergistic effect of ORF and Co,Zn-MOF. For the ORF@Co,Zn-MOF@Si / EP sample, it has the lowest smoke density level, which is mainly related to the synergistic effect of ORF, Co,Zn-MOF and the more stable SiO2 structure.

[0059] (9) XRD patterns of residual char after combustion of EP, ORF / EP, Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP and ORF@Co,Zn-MOF@Si / EP are shown below. Figure 10 As shown; for pure EP, broad diffraction peaks can be observed, which are consistent with the characteristic peaks of amorphous carbon; after adding ORF, the diffraction peaks of residual carbon are not significantly different from those of pure EP, indicating that the introduction of ORF has no significant effect on the crystal structure of residual carbon, and both form an amorphous carbon structure; for Co,Zn-MOF / EP, ORF@Co,Zn-MOF / EP and ORF@Co,Zn-MOF@Si / EP coatings, the residual carbon layer after combustion has changed significantly. It can be seen that a series of new diffraction peaks are generated at 31.3° and 35.6°, which correspond to the (220) and (311) crystal planes of Co3O4, respectively, while the characteristic diffraction peaks at 33.9°, 55.7°, 62.1° and 67.1° correspond to the (002), (110), (103) and (201) crystal planes of ZnO, respectively; the generation of metal oxides can play a catalytic role, effectively promoting the generation of carbon, thereby enhancing the strength and quality of the carbon layer.

Claims

1. A method for preparing a bimetallic MOF organic fiber-based fire-retardant coating, comprising the following steps: (1) Preparation of ORF@Co, Zn-MOF@Si composite flame retardant Preparation of ORF@Co,Zn-MOF hybrid: Algae fibers were dispersed in methanol and ultrasonically treated with a probe for 30 minutes to obtain an algae fiber suspension; then, zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)3·6H2O) were added to the algae fiber suspension and stirred for 60 minutes to form a brown suspension a; next, 2-methylimidazole was dissolved in 30 mL of methanol to form a transparent solution b; solution b was slowly added to suspension a and magnetically stirred for 30 minutes; the resulting mixture of a and b was allowed to stand at room temperature for 16 hours, washed three times by centrifugation with ethanol, and dried in a vacuum oven at 40 °C to obtain the ORF@Co,Zn-MOF hybrid; b. Preparation of ORF@Co, Zn-MOF@Si composite flame retardant: Hexadecyltrimethylammonium bromide was dissolved in a mixture of ethanol and water, and ORF@Co, Zn-MOF hybrid was added to the mixture. After ultrasonic dispersion for 10 minutes, tetraethyl orthosilicate was slowly added to the mixture and stirred for 30 minutes. After stirring for 30 minutes, ammonia water was slowly added to the mixture, and the reaction mixture was stirred again for 10 hours. Finally, the mixture was washed three times with ethanol by centrifugation and freeze-dried to obtain the ORF@Co, Zn-MOF@Si composite flame retardant. (2) Preparation of bimetallic MOF organic fiber-based fire-retardant coating Disperse appropriate amounts of melamine, pentaerythritol, and ammonium polyphosphate in an appropriate amount of water and stir vigorously until a uniform expansion system suspension is obtained. Then, mix and stir the aqueous dispersion of ORF@Co, Zn-MOF@Si composite flame retardant, waterborne epoxy resin emulsion, and curing agent for 10 minutes and pour it into the expansion system suspension at once to obtain a bimetallic MOF organic fiber-based fireproof slurry. Finally, uniformly coat the bimetallic MOF organic fiber-based fireproof slurry onto a steel plate with a sandblasting grade of Sa2. After brushing, cure at room temperature for 7 days and bake at 40℃ for 3 days to obtain a bimetallic MOF organic fiber-based fireproof coating. in, In step (1)a, the mass-volume concentration of seaweed fiber is 0.001-0.002 g / mL; the mass ratio of seaweed fiber to zinc nitrate hexahydrate is 1:15-30; the molar ratio of zinc nitrate hexahydrate to cobalt nitrate hexahydrate is 1:1.5-2.5; the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:4-8; in step (1)b, the mass-volume concentration of hexadecyltrimethylammonium bromide is 0.003-0.005 g / mL; the volume ratio of water to ethanol is 1:1-3; the mass ratio of ORF@Co,Zn-MOF hybrid to hexadecyltrimethylammonium bromide is 1:3-5; the mass-volume ratio of hexadecyltrimethylammonium bromide to tetraethyl orthosilicate is 4:3-5; the mass-volume ratio of hexadecyltrimethylammonium bromide to ammonia is 1:2-3; in step (2), ORF@Co, The Zn-MOF@Si composite flame retardant accounts for 2.0-5.0% of the total mass of the waterborne epoxy resin emulsion, curing agent, expansion system, and ORF@Co, Zn-MOF@Si composite flame retardant.

2. The bimetallic MOF organic fiber-based fire-retardant coating prepared by the method described in claim 1.

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