An intumescent, enhanced, anti-cracking fire-retardant coating for steel structures

Abstract

The present invention discloses an intumescent, enhanced anti-cracking steel structure fire retardant coating, which belongs to the technical field of intumescent fire retardant coatings. The preparation method of the coating comprises the following steps: 1. Preparation of a phosphorylated POSS-based flame retardant grafted modified short fibers; 2. Preparation of a UiO-66 hybrid nanomaterial loaded with intumescent flame retardant coating; 3. Preparation of an intumescent, enhanced anti-cracking steel structure fire retardant coating by adding flame retardant short fibers and modified UiO-66. In the present invention, the phosphorylated POSS-based flame retardant grafted modified short fibers are introduced into the intumescent flame retardant system of the loaded intumescent flame retardant coating UiO-66 nanomaterial, effectively preventing the cracking of the steel structure intumescent fire retardant coating, promoting the expansion of the carbon layer and improving the strength of the carbon layer, synergistically and efficiently improving the heat resistance, carbonization performance and flame retardant performance of the matrix, simple and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of intumescent fire retardant coatings, in particular to an intumescent, enhanced, anti-cracking steel structure fire retardant coating. Background Art

[0002] Steel structural materials are widely used in buildings such as airports, stadiums, and industrial plants due to their light weight, high strength, excellent seismic resistance, simple construction, design flexibility, and environmental friendliness. While steel structural materials are inherently non-flammable, they are highly conductive to heat, and their mechanical strength gradually decreases with increasing temperature. When temperatures exceed 500°C, the mechanical strength of steel structural materials decreases significantly, ultimately losing their support and causing the building to collapse. However, in a fire, temperatures can quickly reach over 700°C, putting extensively used steel structural materials at risk of damage in a very short period of time. According to research, in actual use, the fire resistance limit of exposed steel structural materials is only approximately 15 minutes, significantly complicating firefighting efforts. To increase firefighting time, minimize casualties, and mitigate economic and financial losses, applying fire-retardant coatings to steel structural materials to enhance their fire resistance is a simple, effective, and economical fire prevention measure.

[0003] Applying a fire-retardant coating to the surface of steel structures provides both fireproofing and heat insulation, further preventing a significant loss of mechanical strength that could lead to building collapse. Fire-retardant coatings are categorized as intumescent and non-intumescent. Intumescent coatings are widely used for fire protection of steel structures due to their excellent flame retardancy, cost-effectiveness, and ease of application. Traditional intumescent coatings typically consist of a dehydrating agent, a charring agent, and a foaming agent. These agents contain significant amounts of phosphorus and nitrogen, which provide a synergistic flame-retardant effect. When heated, the dehydrating agent decomposes to release inorganic acids such as phosphoric acid, which promotes the dehydration of the charring agent and polymer matrix to form char. The foaming agent decomposes to produce non-toxic, flame-retardant gases such as ammonia and water vapor, which remove heat from the substrate and expand the molten char layer to form a foam-like structure. Consequently, the intumescent char layer formed on the surface of the steel structure provides heat and oxygen insulation, effectively preventing the substrate from heating up and providing fire-retardant properties for the building.

[0004] Intumescent fire-retardant coatings have the problem of difficulty in uniformly foaming, and are difficult to form a char layer or the char layer that does form has poor thermal insulation properties, which affects their fire resistance and cannot effectively protect the steel structure substrate. Furthermore, the coating is prone to cracking, which cannot prevent corrosion from external media, causing the coating to fall off, resulting in reduced fire resistance or even loss of fire protection. Therefore, it is necessary to develop an intumescent fire-retardant coating with good flame retardancy, uniform foaming, and resistance to cracking. Summary of the Invention

[0005] In order to solve the above problems, the present invention uses phosphorylated POSS-based flame retardant to graft-modify short-cut fibers and adds them to the intumescent flame retardant-modified UiO-66 hybrid nanomaterial intumescent fire retardant coating for steel structures, thereby helping to improve the problems of poor charring and thermal insulation performance and easy cracking of traditional intumescent fire retardant coatings, and constructing an enhanced intumescent fire retardant coating for steel structures that integrates smoke suppression, toxicity reduction, high efficiency flame retardancy and anti-cracking.

[0006] A first aspect of the present invention provides a method for preparing a flame retardant modified chopped carbon fiber material, comprising the following steps:

[0007] 1. Synthesis of A-POSS solid: 3-aminopropyltriethoxysilane was dissolved in anhydrous methanol solution, mixed with hydrochloric acid solution, and allowed to react for a period of time. After solid-liquid separation, the obtained product was A-POSS solid;

[0008] 2. Preparation of phosphorylated POSS-based flame retardant grafted modified chopped fibers: dissolve the A-POSS solid obtained in step 1 in water, heat it to 45-50°C, add formaldehyde, and stir thoroughly for 30-40 minutes. Then heat it to 55-60°C, add phosphorous acid, and after the solution is clarified, add chopped carbon fibers, heat it to 85-95°C, stir and react, separate the solid and liquid, and dry it. The resulting fiber material is a flame retardant modified chopped carbon fiber material.

[0009] Furthermore, in step 1, the volume ratio of 3-aminopropyltriethoxysilane to anhydrous methanol is 1:7.8 to 1:10.

[0010] Furthermore, the mass concentration of the hydrochloric acid solution in step 1 is 30-40%.

[0011] Furthermore, in step 1, the ratio of 3-aminopropyltriethoxysilane to the hydrochloric acid solution is 1:1.4 to 1:2.

[0012] Furthermore, the mixing time in step 1 is 1 to 5 days.

[0013] Furthermore, the static reaction time in step 1 is 1 to 10 days.

[0014] Furthermore, the mass ratio of the A-POSS solid to water in step 2 is 1:100 to 20:100.

[0015] Furthermore, the molar ratio of NH bonds to formaldehyde in the A-POSS solid in step 2 is 1:16 to 1:32.

[0016] Furthermore, the molar ratio of NH bonds to phosphorous acid in the A-POSS solid in step 2 is 1:16 to 1:32.

[0017] Furthermore, in step 2, the mass ratio of the A-POSS solid to the formaldehyde solution is 1:5 to 1:10.

[0018] Furthermore, the mass ratio of the A-POSS solid to the phosphorous acid in step 2 is 1:1 to 1:2.

[0019] Furthermore, the length of the chopped carbon fibers in step 2 is 0.1 to 10 mm.

[0020] Furthermore, the stirring reaction time in step 2 is 8 to 12 hours.

[0021] The present invention provides a flame retardant modified chopped carbon fiber material prepared according to the method.

[0022] A second aspect of the present invention provides a method for preparing a UiO-66 hybrid nanomaterial loaded with an intumescent flame retardant coating, comprising the following steps:

[0023] S1. Preparation of UiO-66 micro-nanomaterials: dissolving a transition metal salt compound and an organic ligand in a solvent, mixing them uniformly, and reacting them under a certain temperature to obtain a suspension; collecting the suspension by centrifugation, washing the suspension with methanol or water multiple times, and finally drying the obtained solid to obtain the UiO-66 micro-nanomaterial.

[0024] S2. Preparation of flame retardant modified solution: dissolving chitosan in a solvent to prepare a chitosan solution of a certain concentration; dissolving ammonium polyphosphate in a solvent to prepare an ammonium polyphosphate solution of a certain concentration;

[0025] S3. Preparation of UiO-66 hybrid nanomaterials loaded with intumescent flame retardant coating:

[0026] a. Immersing the UiO-66 micro-nanomaterial obtained in step S1 in the chitosan solution in step S2, then collecting and washing the particle precipitate to remove unadsorbed chitosan particles;

[0027] b. Immersing the particle precipitate obtained in step a in the prepared ammonium polyphosphate solution, collecting the particle precipitate after a certain period of time and washing it to remove the unadsorbed ammonium polyphosphate particles, thereby completing the expansion flame retardant modification of the UiO-66 nanomaterial;

[0028] c. Repeat steps a to b 3 to 10 times.

[0029] Furthermore, the transition metal salt compound in step S1 is one or more metal zirconium salts such as zirconium chloride, zirconium sulfate, and zirconium acetate.

[0030] Furthermore, the organic ligand in step S1 is one or more of terephthalic acid, trimesic acid and dimethylimidazole.

[0031] Furthermore, the solvent in step S1 is one or more of water, methanol, anhydrous ethanol and N,N-dimethylformamide.

[0032] Furthermore, the concentration of the transition metal salt compound in the suspension in step S1 is 0.01 to 0.05 mol / L.

[0033] Furthermore, the concentration of the organic ligand in the suspension in step S1 is 0.01 to 0.05 mol / L.

[0034] Furthermore, the certain temperature in step S1 is 100-180°C.

[0035] Furthermore, the reaction time in step S1 is 10 to 48 hours.

[0036] Furthermore, the centrifugal speed in step S1 is 1000-9000 r / min, and the centrifugal time is 3-10 min.

[0037] Furthermore, the drying temperature in step S1 is 45-120° C., and the drying time is 1-8 hours.

[0038] Furthermore, the solvent in step S2 is one or more of water, acetic acid, and N,N-dimethylformamide.

[0039] Furthermore, the chitosan solution in step S2 has a concentration of 0.5 to 5 wt%.

[0040] Furthermore, the concentration of the ammonium polyphosphate solution in step S2 is 0.5-5 wt%.

[0041] Furthermore, in step S3, the soaking time in step a and step b is 1 to 10 minutes.

[0042] The present invention provides a UiO-66 hybrid nanomaterial loaded with an expansion flame-retardant coating prepared according to the above method.

[0043] A third aspect of the present invention provides a method for preparing an intumescent, enhanced anti-cracking fire retardant coating for steel structures, comprising the following steps:

[0044] Ⅰ. Preparation of base material: weigh the film-forming agent and curing agent and stir until a uniform mixture is obtained;

[0045] II. Preparation of intumescent, reinforced anti-cracking fire retardant coating for steel structures: Take the base material and the UiO-66 hybrid nanomaterial loaded with intumescent flame retardant coating, mix and stir to form a uniform dispersion system; then, add the flame retardant modified chopped carbon fiber material to the uniform dispersion system and disperse it evenly to obtain the intumescent, reinforced anti-cracking fire retardant coating for steel structures.

[0046] Furthermore, the film-forming agent in step I includes one or more of epoxy resin, polyurethane, acrylic acid, and water-based silicone acrylic emulsion.

[0047] Furthermore, the curing agent in step I includes one or a combination of ethylenediamine, diethylenetriamine, triethylenetetramine, and 4,4-diaminodiphenylmethane.

[0048] Furthermore, in step I, the ratio of the film-forming agent to the curing agent is 1.5:1 to 5:1.

[0049] Furthermore, in step II, the base material accounts for 92.0-99.0% of the total weight of the uniformly dispersed system.

[0050] Furthermore, in step II, the UiO-66 hybrid nanomaterial supporting the intumescent flame retardant coating accounts for 1 to 8.0% of the total weight of the uniformly dispersed system.

[0051] Preferably, the UiO-66 hybrid nanomaterial supporting the intumescent flame retardant coating in step II accounts for 1 to 2.0% of the total weight of the uniformly dispersed system.

[0052] Furthermore, in step II, the flame retardant modified chopped carbon fiber material accounts for 0.5 to 10% of the uniformly dispersed system.

[0053] Preferably, the flame retardant modified chopped carbon fiber material in step II accounts for 0.8-1.2% of the uniformly dispersed system.

[0054] The present invention provides an intumescent, enhanced, anti-cracking fire-retardant coating for steel structures prepared according to the method.

[0055] The invention provides an application of an intumescent, enhanced anti-cracking steel structure fire retardant coating in the field of fire prevention and fire retardant product preparation.

[0056] Furthermore, the application includes the following steps:

[0057] The intumescent, enhanced anti-cracking steel structure fire retardant coating is brushed on the surface of the substrate, and after brushing, it is cured for 1 to 5 days, and then baked at 60 to 120° C. for 1 to 3 days to obtain a high-temperature resistant intumescent, enhanced anti-cracking steel structure fire retardant coating.

[0058] Furthermore, the substrate includes buildings, vehicles, panels and various objects that require fire protection.

[0059] The present invention has the following beneficial effects:

[0060] (1) The method of grafting modified chopped fibers with phosphorylated POSS-based flame retardants in the present invention is stable and reliable, imparting flame retardant properties to the chopped carbon fibers, effectively improving their dispersibility and compatibility with the matrix material, and the well-dispersed flame retardant modified chopped fibers are expected to solve the problem of easy cracking of fire-retardant coatings on steel structures;

[0061] (2) In the present invention, the UiO-66 hybrid nanomaterial is modified with an intumescent flame retardant to effectively enhance the flame retardant properties of the UiO-66 nanomaterial, and organically combine with the metal-organic framework's inherent metal catalytic carbonization, smoke suppression and toxicity reduction, and adsorption properties to improve the flame retardant properties of the intumescent fire retardant coating in a diversified manner;

[0062] (3) The intumescent steel structure fire retardant coating containing phosphorylated POSS-based flame retardant grafted modified chopped fibers and intumescent flame retardant modified UiO-66 hybrid nanomaterials added in the present invention exerts a synergistic and efficient flame retardant effect, thereby comprehensively improving the fire safety performance of the steel structure fire retardant coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The infrared spectra of UiO-66 before and after modification.

[0064] Figure 2 XRD patterns of UiO-66 before and after modification.

[0065] Figure 3 These are the SEM images of UiO-66 before and after modification, where a is before flame retardant modification and b is after flame retardant modification.

[0066] Figure 4 These are SEM images of carbon fiber before and after modification, where a is 200um carbon fiber before flame retardant modification, and b is 200um carbon fiber after flame retardant modification.

[0067] Figure 5 These are photos of the modified resin before and after the cone calorimetry test, where a is the pure epoxy resin sample and b is the epoxy resin modified with nanomaterials. DETAILED DESCRIPTION

[0068] The present invention will be further explained and illustrated below in conjunction with the attached tables and examples, but the protection scope of the present invention is not limited to the following examples.

[0069] Example 1

[0070] A method for preparing phosphorylated POSS-based flame retardant grafted modified short fibers comprises the following steps:

[0071] 1. Synthesis of A-POSS solid.

[0072] 90 mL of 3-aminopropyltriethoxysilane (APTES) was completely dissolved in 700 mL of anhydrous methanol solution, mixed with 123 mL of hydrochloric acid solution and stirred for 3 days, and allowed to react for 10 days. After solid-liquid separation, the obtained product was A-POSS solid.

[0073] 2. Preparation of phosphorylated POSS-based flame retardant grafted modified chopped fibers.

[0074] 3.52 g of A-POSS solid was completely dissolved in 500 mL of deionized water, the temperature was raised to 45 ° C, 26 g of formaldehyde solution was added, and the mixture was stirred thoroughly for 30 minutes. The temperature was then raised to 55 ° C, 5.853 g of phosphorous acid was added, and after the solution was clarified, 0.2 mm short-cut carbon fiber was added. The temperature was raised to 85 ° C, and the mixture was stirred thoroughly for 12 hours. After solid-liquid separation and drying, the obtained fiber material was the flame-retardant modified short-cut carbon fiber material.

[0075] A method for preparing a UiO-66 hybrid nanomaterial loaded with an intumescent flame retardant coating comprises the following steps:

[0076] 1. Preparation of UiO-66 micro-nanomaterials.

[0077] 0.714 g of zirconium chloride and 0.5075 g of 2-aminoterephthalic acid were dissolved in 80 mL of N,N-dimethylformamide solution, mixed evenly, and reacted at 120°C for 12 hours to obtain a clear suspension. The suspension was centrifuged at 3000 r / min for 6 minutes to collect the precipitate, washed three times with methanol solution, and finally dried in a vacuum oven at 80°C for 2 hours to obtain the product, the UiO-66 metal-organic framework material.

[0078] 2. Preparation of flame retardant modified solution.

[0079] 1 g of chitosan powder was weighed and dissolved in 100 mL of 1 wt% acetic acid solution to prepare a chitosan solution with a concentration of 1 wt%; 2 g of ammonium polyphosphate was weighed and dissolved in 100 mL of deionized water to prepare an ammonium polyphosphate solution with a concentration of 2 wt%.

[0080] 3. Preparation of UiO-66 hybrid nanomaterials loaded with intumescent flame retardant coating.

[0081] (1) The obtained UiO-66 sample was immersed in the prepared 1 wt% chitosan solution for 5 min, and the particle precipitate was collected and washed with deionized water to remove the unadsorbed chitosan particles;

[0082] (2) The precipitate obtained in (1) was immersed in a prepared 2 wt% ammonium polyphosphate solution for 5 min, and the granular precipitate was collected and washed with deionized water to remove the unadsorbed ammonium polyphosphate particles. Thus, the expansion flame retardant modification of the UiO-66 nanomaterial was completed.

[0083] (3) Repeat the assembly process of steps (1) to (2), shortening the immersion time to 1 min, until 5 modifications are achieved.

[0084] A method for preparing an intumescent, enhanced, anti-cracking steel structure fire retardant coating containing flame-retardant chopped fibers and modified UiO-66, comprising the following steps:

[0085] 47.383g of epoxy resin, 2.0g of UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating, 0.6g of 0.2mm phosphorylated POSS-based flame retardant-grafted modified chopped carbon fibers, and 10.617g of 4,4-diaminodiphenylmethane were mixed until homogeneous and mechanically stirred for 5h to form a uniformly dispersed intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped carbon fibers and modified UiO-66. The uniformly mixed coating was then applied to the pretreated substrate surface, cured at room temperature for 3 days, and baked at 120°C for 1 day to obtain a high-temperature-resistant intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped carbon fibers and modified UiO-66.

[0086] Example 2

[0087] A method for preparing phosphorylated POSS-based flame retardant grafted modified short fibers is prepared by referring to the steps in Example 1;

[0088] A method for preparing a UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating is prepared by referring to the steps in Example 1;

[0089] A method for preparing an intumescent, enhanced, anti-cracking steel structure fire retardant coating containing flame-retardant chopped fibers and modified UiO-66, comprising the following steps:

[0090] 47.791g of epoxy resin, 1.2g of UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating, 0.6g of 0.2mm phosphorylated POSS-based flame retardant-grafted modified chopped carbon fibers, and 10.709g of 4,4-diaminodiphenylmethane were mixed until homogeneous and mechanically stirred for 5h to form a uniformly dispersed intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped fibers and modified UiO-66. The uniformly mixed coating was then applied to the pretreated substrate surface, cured at room temperature for 3 days, and baked at 120°C for 1 day to obtain a high-temperature-resistant intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped fibers and modified UiO-66.

[0091] Example 3

[0092] A method for preparing phosphorylated POSS-based flame retardant grafted modified short fibers is prepared by referring to the steps in Example 1;

[0093] A method for preparing a UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating is prepared by referring to the steps in Example 1;

[0094] A method for preparing an intumescent, enhanced, anti-cracking steel structure fire retardant coating containing flame-retardant chopped fibers and modified UiO-66, comprising the following steps:

[0095] 48.284g of epoxy resin, 0.6g of UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating, 0.6g of 0.2mm phosphorylated POSS-based flame retardant-grafted modified chopped carbon fibers, and 10.516g of 4,4-diaminodiphenylmethane were mixed until homogeneous and mechanically stirred for 5h to form a uniformly dispersed intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped fibers and modified UiO-66. The uniformly mixed coating was then applied to the pretreated substrate surface, cured at room temperature for 3 days, and baked at 120°C for 1 day to obtain a high-temperature-resistant intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped fibers and modified UiO-66.

[0096] Example 4

[0097] A method for preparing phosphorylated POSS-based flame retardant grafted modified short fibers is prepared by referring to the steps in Example 1;

[0098] A method for preparing a UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating is prepared by referring to the steps in Example 1;

[0099] A method for preparing an intumescent, enhanced, anti-cracking steel structure fire retardant coating containing flame-retardant chopped fibers and modified UiO-66, comprising the following steps:

[0100] 48.530g of epoxy resin, 0.3g of UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating, 0.6g of 0.2mm phosphorylated POSS-based flame retardant-grafted modified chopped carbon fibers, and 10.570g of 4,4-diaminodiphenylmethane were mixed until homogeneous and mechanically stirred for 5h to form a uniformly dispersed intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped fibers and modified UiO-66. The uniformly mixed coating was then applied to the pretreated substrate surface, cured at room temperature for 3 days, and baked at 120°C for 1 day to obtain a high-temperature-resistant intumescent, reinforced, and crack-resistant fire-retardant coating for steel structures containing the flame-retardant chopped fibers and modified UiO-66.

[0101] Comparative Example 1

[0102] Weigh 49.269g of epoxy resin and 10.731g of 4,4-diaminodiphenylmethane and stir until homogeneous. Mechanically stir to form a uniformly dispersed resin coating. Apply the uniformly mixed resin coating to the pretreated substrate surface by brushing. After brushing, cure at room temperature for 3 days and bake at 120°C for 1 day to obtain a coating.

[0103] Comparative Example 2

[0104] 48.777g of epoxy resin, 0.6g of 0.2mm phosphorylated POSS-based flame retardant-grafted modified chopped carbon fibers, and 10.623g of 4,4-diaminodiphenylmethane were weighed and mixed until uniform. Mechanically stirred and dispersed for 5 hours to form a uniformly dispersed fire-retardant coating for steel structures reinforced with flame-retardant chopped carbon fibers. The uniformly mixed fire-retardant coating was applied to the pretreated substrate surface. After application, the coating was cured at room temperature for 3 days and then baked at 120°C for 1 day to obtain a fire-retardant coating for steel structures reinforced with flame-retardant chopped fibers.

[0105] Comparative Example 3

[0106] 48.284g of epoxy resin, 1.2g of UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating, and 10.516g of 4,4-diaminodiphenylmethane were mixed until homogeneous and mechanically stirred for 5h to form an intumescent, enhanced, and crack-resistant fire-retardant coating for steel structures made of modified UiO-66. The uniformly mixed fire-retardant coating was applied to the pretreated substrate surface by brushing. After application, the coating was cured at room temperature for 3 days and then baked at 120°C for 1 day to obtain a high-temperature-resistant intumescent fire-retardant coating for steel structures made of modified UiO-66.

[0107] Comparative Example 4

[0108] 48.284g of epoxy resin, 1.2g of UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating, 0.6g of 0.2mm chopped carbon fibers, and 10.516g of 4,4-diaminodiphenylmethane were weighed and mixed until uniform. Mechanical stirring and dispersion were performed for 5 hours to form a uniformly dispersed intumescent, reinforced, and crack-resistant steel structure fire retardant coating containing the added chopped carbon fibers and modified UiO-66. The uniformly mixed fire retardant coating was applied to the pretreated substrate surface, cured at room temperature for 3 days, and baked at 120°C for 1 day to obtain a high-temperature resistant intumescent, reinforced, and crack-resistant steel structure fire retardant coating containing the added chopped carbon fibers and modified UiO-66.

[0109] Comparative Example 5

[0110] 48.284g of epoxy resin, 1.2g of UiO-66 nanomaterial, 0.6g of 0.2mm phosphorylated POSS-based flame retardant-grafted modified chopped fibers, and 10.570g of 4,4-diaminodiphenylmethane were weighed and mixed until homogeneous. Mechanical stirring and dispersion were performed for 5 hours to form a uniformly dispersed fire-retardant coating for steel structures reinforced with flame-retardant chopped fibers and UiO-66. The uniformly mixed fire-retardant coating was applied to the pretreated substrate surface, cured at room temperature for 3 days, and baked at 120°C for 1 day to obtain a high-temperature-resistant fire-retardant coating for steel structures reinforced with flame-retardant chopped fibers and modified UiO-66.

[0111] Comparative Example 6

[0112] Weigh 48.284g of epoxy resin, 1.2g of ammonium polyphosphate / chitosan intumescent flame-retardant blend, and 10.570g of 4,4-diaminodiphenylmethane and stir until uniform. Mechanically stir and disperse for 5 hours to form a uniformly dispersed intumescent steel structure fire retardant coating. Apply the uniformly mixed fire retardant coating to the pretreated substrate surface. After application, cure at room temperature for 3 days and bake at 120°C for 1 day to obtain a high-temperature-resistant intumescent steel structure fire retardant coating.

[0113] Comparative Example 7

[0114] Weigh 48.284g of epoxy resin, 1.2g of ammonium polyphosphate / pentaerythritol traditional intumescent flame-retardant blend, and 10.570g of 4,4-diaminodiphenylmethane and stir until uniform. Mechanically stir and disperse for 5 hours to form a uniformly dispersed traditional intumescent fire-retardant coating for steel structures. Apply the uniformly mixed fire-retardant coating to the pretreated substrate surface. After application, cure at room temperature for 3 days and bake at 120°C for 1 day to obtain a high-temperature-resistant traditional intumescent fire-retardant coating for steel structures.

[0115] Table 1 Sample formula of comparative examples 1 to 7 and examples 1 to 3

[0116]

[0117]

[0118] Result detection

[0119] Cone calorimetry test process: Composite material samples prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were respectively installed in the test apparatus. The power of the radiation cone was set to 35 kW. The cone calorimeter was started to perform thermal radiation and collect test data in real time. Parameters such as the heat release rate (PHRR), total heat release (THR), total smoke release (TSR), and real-time mass (MASS) of the material were calculated. After the preset test time was reached, the thermal radiation of the radiation cone was stopped, and the following data were obtained:

[0120] Table 2 Cone calorimetry test data of Comparative Examples 1 to 7 and Examples 1 to 3

[0121]

[0122] The peak heat release rate (PHRR) indicates the typical combustion characteristics of the material. Compared with the comparative pure epoxy resin (Comparative Example 1), the PHRR value of the embodiment is high, which proves that after adding the expanded flame retardant modified UiO-66 nano flame retardant system and the flame retardant modified short fibers, the flame retardant properties are improved, and the flame retardant properties of the composite material with the flame retardant modified short fibers added alone are also improved; the PHRR values ​​of Examples 2 to 4 gradually improve with the increase of the amount of expanded flame retardant modified UiO-66 added, which proves that within a certain range, the flame retardant properties are enhanced with the increase of the amount of expanded flame retardant modified UiO-66 nano flame retardant system added, however, when the amount of expanded flame retardant modified UiO-66 added is further increased ( In Example 1), the flame retardant performance deteriorates, which may be caused by the agglomeration phenomenon caused by excessive addition of nanoparticles; compared with Comparative Examples 3 to 4, Example 2 has better flame retardant performance than adding no flame retardant modified UiO-66 and adding flame retardant modified short fibers when adding the same content of intumescent flame retardant modified UiO-66 and adding ordinary short fibers; compared with Comparative Example 2, Example 3 and Comparative Examples 5 to 7 have better effects on adding UiO-66 nano flame retardant modified by intumescent flame retardant on the basis of adding the same amount of flame retardant modified short fibers than the composite materials of adding nanomaterials alone, intumescent flame retardant for modification (APP / CS), and traditional intumescent flame retardant (APP / pentaerythritol). The expansion effect of the composite material with UiO-66 nano flame retardant modified by intumescent flame retardant is as follows: Figure 5 As shown in (b), the UiO-66 nano flame retardant is an integrated intumescent flame retardant system that synergistically acts as a dehydrating agent / foaming agent to form a stable intumescent carbon layer, protecting the substrate material from the continuous impact of flame and heat. In summary, the composite material of the UiO-66 metal frame modified with a certain amount of APP / CS intumescent flame retardant and the flame-retardant modified short-cut fiber exhibits excellent flame retardant properties. The flame retardant properties of the composite material of the UiO-66 metal frame modified with APP / CS intumescent flame retardant and the flame-retardant modified short-cut fiber alone, as well as the composite material added with general intumescent flame retardants, nanomaterials and carbon fiber effects, are not good enough.

[0123] Similarly, the above conclusion can be drawn through values ​​such as the total heat release (THR) that represents the total amount of heat released from the ignition of the material to the extinction of the flame, and the real-time mass (mass) that represents the trend of decomposition and weight loss during the combustion process of the material.

[0124] Strength test process: Samples of the fire-resistant composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were clamped and fixed on a test device. Tensile force was applied and the load was gradually increased until the sample broke. During the test, changes in load and displacement were recorded to obtain the following data:

[0125] Table 3 Strength test data of comparative examples and examples 1 to 3

[0126]

[0127] The introduction of a certain amount of nanomaterials and reinforced chopped fibers into composite materials can effectively enhance the mechanical properties of composite materials. As shown in the above table, the tensile strength, tensile modulus and elongation at break of all samples with chopped fibers added, whether modified or not (except Example 1), have increased. When the amount of chopped fibers added is constant, the strength of Examples 2 to 4 increases with the increase in the amount of expanded flame-retardant modified UiO-66 added. This is because the introduction of nanomaterials can increase the interface effect and thus improve the mechanical properties. However, in Example 1, when the amount of expanded flame-retardant modified UiO-66 added exceeds a certain range, a large amount of nanomaterials agglomerate and cause stress concentration, thereby causing the mechanical properties of the composite material to deteriorate. For Comparative Examples 2 to 7, since no chopped fibers are added in Comparative Example 3 but nanomaterials are added, the mechanical properties are slightly improved compared to Comparative Example 1. The data of Comparative Examples 4 to 5 are better than those of Comparative Examples 2 and 6 to 7, indicating that nanomaterials are beneficial to enhancing the mechanical properties of composite materials.

[0128] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing an intumescent, enhanced anti-cracking fire retardant coating for steel structures, characterized in that: The steps include: I. Preparation of base material: Weigh a film-forming agent and a curing agent and stir until a uniform mixture is obtained; the film-forming agent is an epoxy resin; the curing agent includes one or a combination of ethylenediamine, diethylenetriamine, triethylenetetramine, and 4,4-diaminodiphenylmethane; II. Preparation of an intumescent, reinforced, anti-cracking steel structure fire retardant coating: a base material and a UiO-66 hybrid nanomaterial loaded with an intumescent flame retardant coating are mixed and stirred to form a uniform dispersion system; then, a flame retardant modified chopped carbon fiber material is added to the uniform dispersion system and dispersed uniformly to obtain an intumescent, reinforced, anti-cracking steel structure fire retardant coating; The flame retardant modified chopped carbon fiber material accounts for 0.5-10% of the total weight of the uniformly dispersed system; The UiO-66 hybrid nanomaterial loaded with the intumescent flame retardant coating accounts for 1 to 8.0% of the total weight of the uniformly dispersed system; The method for preparing the flame retardant modified chopped carbon fiber material comprises the following steps: (1) Synthesis of A-POSS solid: 3-aminopropyltriethoxysilane was dissolved in anhydrous methanol solution and mixed with hydrochloric acid solution. The mixture was allowed to react for a period of time. After solid-liquid separation, the resulting product was A-POSS solid. (2) Preparation of phosphorylated POSS-based flame retardant grafted modified chopped fibers: The A-POSS solid obtained in step (1) was dissolved in water, heated to 45-50°C, formaldehyde was added, and the mixture was stirred for 30-40 min. The mixture was then heated to 55-60°C, phosphorous acid was added, and after the solution was clarified, chopped carbon fibers were added. The mixture was heated to 85-95°C, stirred for reaction, and solid-liquid separation and drying were performed to obtain a flame-retardant modified chopped carbon fiber material. The preparation method of the UiO-66 hybrid nanomaterial loaded with an intumescent flame-retardant coating comprises the following steps: S1. Preparation of UiO-66 micro-nanomaterials: dissolving a transition metal salt compound and an organic ligand in a solvent, mixing them uniformly, and reacting them under a certain temperature to obtain a suspension; collecting the precipitate from the suspension by centrifugation, washing it multiple times with methanol or water, and finally drying the obtained solid to obtain the UiO-66 micro-nanomaterial; the transition metal salt compound is a metal zirconium salt; and the organic ligand is one or more of terephthalic acid, trimesic acid, and dimethylimidazole; S2. Preparation of flame retardant modified solution: dissolving chitosan in a solvent to prepare a chitosan solution of a certain concentration; dissolving ammonium polyphosphate in a solvent to prepare an ammonium polyphosphate solution of a certain concentration; S3. Preparation of UiO-66 hybrid nanomaterials loaded with intumescent flame retardant coating: a. Immersing the UiO-66 micro-nanomaterial obtained in step S1 in the chitosan solution in step S2, then collecting and washing the particle precipitate to remove unadsorbed chitosan particles; b. Immersing the particle precipitate obtained in step a in the prepared ammonium polyphosphate solution, collecting the particle precipitate after a certain period of time and washing it to remove the unadsorbed ammonium polyphosphate particles, thereby completing the expansion flame retardant modification of the UiO-66 nanomaterial; c. Repeat steps a to b 3 to 10 times.

2. The preparation method according to claim 1, characterized in that In step I, the ratio of the film-forming agent to the curing agent is 1.5:1 to 5:

1.

3. The preparation method according to claim 1, characterized in that In step (1), the volume ratio of 3-aminopropyltriethoxysilane to anhydrous methanol solution is 1:7.8~1:10; the ratio of 3-aminopropyltriethoxysilane to hydrochloric acid solution is 1:1.4~1:

2.

4. The preparation method according to claim 1, wherein In step (2), the mass ratio of the A-POSS solid to water is 1:100 to 20:100; the molar ratio of the NH bonds in the A-POSS solid to formaldehyde is 1:16 to 1:32; and the molar ratio of the NH bonds in the A-POSS solid to phosphorous acid is 1:16 to 1:

32.

5. The preparation method according to claim 1, wherein In step (2), the length of the chopped carbon fibers is 0.1 to 10 mm.

6. The preparation method according to claim 1, wherein In step S1, the metal zirconium salt is one or more of zirconium chloride, zirconium sulfate, and zirconium acetate; and the solvent is one or more of water, methanol, anhydrous ethanol, and N,N-dimethylformamide.

7. The preparation method according to claim 1, characterized in that In step S1, the concentration of the transition metal salt compound in the suspension is 0.01-0.05 mol / L; the concentration of the organic ligand in the suspension is 0.01-0.05 mol / L.

8. The preparation method according to claim 1, characterized in that In step S2, the solvent is one or more of water, acetic acid, and N,N-dimethylformamide; the concentration of the chitosan solution is 0.5-5 wt%; and the concentration of the ammonium polyphosphate solution is 0.5-5 wt%.

9. An intumescent, enhanced anti-cracking fire retardant coating for steel structures, characterized in that: The intumescent, enhanced anti-cracking steel structure fire retardant coating is prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the intumescent, enhanced anti-cracking fire retardant coating for steel structures as claimed in claim 9 in the field of fire prevention and fire retardant product preparation.

Images