Preparation method of high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating

Abstract

The application discloses a preparation method of high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof paint, and the preparation method comprises the following steps: (1) preparation of a base material; (2) preparation of CNP hybrid material; (3) preparation of CNP@CH hybrid material; (3) preparation of CNP@CH@Si hybrid material; and (4) preparation of high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof paint. The modified CNP@CH@Si nano hybrid material is combined with the water-based intumescent fireproof paint, so that the defects of low carbon layer strength, uneven expansion and poor flame-retardant performance of the current water-based fireproof paint are solved; the obtained fireproof paint can form a carbon layer with high strength and uniform expansion under high temperature, can effectively play a barrier role, and can inhibit heat transfer. The application is mainly used for steel structure fire protection, can form an expanded carbon layer to protect the steel structure when a fire occurs, and can prolong precious rescue time. The water-based intumescent fireproof paint has the advantages of easy raw material acquisition, simple preparation, low cost, environmental protection and wide industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of preparation methods of epoxy composite coatings, and particularly relates to a preparation method and application of a high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating. BACKGROUND

[0002] At high temperatures, bare steel structures reach the failure temperature of 500℃ in only 15 min. In this case, the potential high fire risk of steel structures urgently needs to be addressed. Painting water-based intumescent fireproofing coatings on the surface of steel structures is a simple, efficient and environmentally friendly means. Water-based intumescent fireproofing coatings expand and form a porous carbon layer under high temperature, which acts as a barrier to heat, air and pyrolysis products, thereby delaying the failure temperature of steel structures and prolonging valuable rescue time. However, the carbon layer formed by water-based intumescent fireproofing coatings has defects, such as low carbon layer strength, poor oxidation resistance, and uneven expansion. Therefore, it is necessary to add flame retardant fillers to improve these defects. In this context, different flame retardant systems (FRs) have been developed by researchers. The earliest and most effective FRs are halogen-based products, but they are prohibited due to their high toxicity. Then, halogen-free flame retardants such as phosphorus and nitrogen-containing compounds were developed as alternatives. In recent years, environmentally friendly inorganic two-dimensional nanosheet materials have received extensive attention as flame retardants for polymers. Compared with other two-dimensional materials, graphite phase carbon nitride (CN) has the advantages of simple preparation, low cost, large specific surface area, excellent thermal and chemical stability, and has been studied in the fields of photocatalysis, energy, flame retardants and mechanical reinforcing agents. However, when graphite phase carbon nitride is used as a flame retardant alone, the effect is limited, and it needs to be further functionalized on its surface to give it multifunctionality, thereby further enhancing its flame retardant ability. Therefore, we synthesized a multifunctional flame retardant (CNP@CH@Si) based on the combination of inorganic and organic nanostructures to enhance the fireproofing performance of water-based intumescent fireproofing coatings. The flame retardant CNP@CH@Si is composed of three layers, each with specific functions. The chitosan layer is self-assembled on the surface of graphite phase carbon nitride coated with polydopamine, and then grafted with silane coupling agent KH-560 to prepare a core-shell structure. Among them, graphite phase carbon nitride can provide a barrier function to block the transfer of heat and flammable gases; chitosan not only provides a large amount of carbon source and nitrogen source, but also effectively improves the dispersibility of graphite phase carbon nitride in water-based intumescent fireproofing coatings; the silane coupling agent KH-560 coated on the surface of chitosan can enhance the interaction between the flame retardant and the water-based epoxy resin; under fire, the silane coupling agent KH-560 is converted into a silica shell layer at high temperatures, while the chitosan decomposes to form a hollow structure, which can greatly enhance the smoke adsorption capacity and flame retardant path, effectively enhancing the flame retardant and smoke suppression performance. The use of efficient flame retardant CNP@CH@Si improves the carbon layer strength and expansion mode of water-based intumescent fireproofing coatings, thereby enhancing the fireproofing performance of water-based intumescent fireproofing coatings. SUMMARY

[0003] The application provides a preparation method of a high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating and expands the application of the CNP@CH@Si flame retardant in the field of fireproof coatings.

[0004] To achieve the above technical purposes, the application adopts the following technical scheme:

[0005] A preparation method of a high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating, characterized by comprising the following steps:

[0006] S1: Preparation of a base material: a certain amount of water-based epoxy resin, a curing agent, melamine polyphosphate, dipentaerythritol and melamine are weighed, stirred at a speed of 300 r / min for 3 h, and then stirred at a speed of 60 r / min for 2 h to obtain a uniformly mixed base material;

[0007] S2: Preparation of a CNP hybrid material: first, a certain amount of graphite carbon nitride is ultrasonically dispersed in 200 mL of deionized water, then 0.32 g of Tris-HCl is added, then the pH is adjusted to 8.5 with a 0.1M NaOH solution, then a certain amount of dopamine hydrochloride is added, and stirring is continued at room temperature for 16 h, the product is centrifuged with water and washed 3 times, and dried to obtain a CNP hybrid material;

[0008] S3: Preparation of a CNP@CH hybrid material: a certain amount of CNP is ultrasonically dispersed in 50 mL of deionized water, then transferred to a three-necked flask, the three-necked flask is placed in an oil bath at 60 DEG C, stirring is continued at 60 DEG C to form solution A, then a certain amount of chitosan and a certain amount of acetic acid are dispersed in 100 mL of deionized water to form solution B, and solution B is added to solution A, and the reaction is carried out at 60 DEG C for 6 h, the product is centrifuged with water and washed 3 times, and dried to obtain a CNP@CH hybrid material;

[0009] S4: Preparation of a CNP@CH@Si hybrid material: a certain amount of CNP@CH is ultrasonically dispersed in 150 mL of deionized water, then a certain amount of silane coupling agent KH-560 is added dropwise at 60 DEG C, then the reaction is carried out at 60 DEG C for 4 h, the product is centrifuged with water and washed 3 times, and dried to obtain a CNP@CH@Si hybrid material;

[0010] S5: Preparation of a high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating: a certain amount of base material and a certain amount of CNP@CH@Si hybrid material are mixed, a uniformly dispersed system is formed by mechanical stirring for 5 h, then the uniformly dispersed system is brushed on the surface of a steel sheet, and after brushing is completed, the high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating is obtained by curing at room temperature for 7 days.

[0011] Further, the mass ratio of the water-based epoxy resin, the curing agent, the melamine polyphosphate, the dipentaerythritol and the melamine in step S1 is 20:10:6:3:1;

[0012] Further, the mass ratio of the graphite phase carbon nitride and the dopamine hydrochloride in step S2 is 1:4-6;

[0013] Further, the mass ratio of the CNP, the chitosan and the acetic acid in step S3 is 1:1-2:8-12;

[0014] Further, the mass ratio of the CNP@CH and the silane coupling agent KH-560 in step S4 is 1:10-20;

[0015] Further, the CNP@CH@Si hybrid material accounts for 1%-6% of the total mass of the uniform dispersion system in step S5.

[0016] Beneficial effects:

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The preparation method of the high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating provided by the application solves the dangerous characteristics of low carbon layer strength, uneven expansion and poor flame retardant performance of the current water-based fireproof coating, and the obtained water-based intumescent fireproof coating can form a uniform and high-strength expanded carbon layer at high temperature, and the expanded carbon layer has enhanced flame retardant performance and thermal stability, can effectively provide a barrier function to hinder the transmission of heat and combustible gas, and has a protective effect. The application is mainly used for steel structure fire protection, and forms an expanded carbon layer when a fire occurs, blocks the invasion of fire, delays the reaching of the failure temperature of the steel structure, and thus prolongs the precious rescue time. The water-based intumescent fireproof coating has raw materials that are easy to obtain, simple preparation, low cost and environmental protection, and has wide industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 TEM images of CN, CNP, CNP@CH and CNP@CH@Si, wherein A and E are CN, B and F are CNP, C and G are CNP@CH, and D and H are CNP@CH@Si.

[0020] Figure 2 SEM images of the cross sections of EP, CN / EP, CNP / EP, CNP@CH / EP and CNP@CH@Si / EP coatings, wherein A is EP, B is CN / EP, C is CNP / EP, D is CNP@CH / EP, and E is CNP@CH@Si / EP.

[0021] Figure 3Temperature of the back of the steel plate as a function of time after the test by the big plate method.

[0022] Figure 4 Digital pictures of the expanded carbon layer after the test in the furnace, where A is EP, B is CN / EP, C is CNP / EP, D is CNP@CH / EP, E is CNP@CH@Si / EP.

[0023] Figure 5 Scanning electron microscopy pictures of the carbon layer after the test by the big plate, where A is EP, B is CN / EP, C is CNP / EP, D is CNP@CH / EP, E is CNP@CH@Si / EP. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0025] Example:

[0026] A preparation method of a high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating, the specific preparation includes the following steps:

[0027] S1: Preparation of the base material: weigh 50 g of water-based epoxy resin, 25 g of curing agent, 15 g of melamine polyphosphate, 7.5 g of dipentaerythritol, and 2.5 g of melamine, stir at a speed of 300 r / min for 3 h, and then stir at a speed of 60 r / min for 2 h to obtain a uniformly mixed base material;

[0028] S2: Preparation of CNP hybrid material: first, 0.1 g of graphite phase cyanamide is ultrasonically dispersed in 200 mL of deionized water, then 0.32 g of Tris-HCl is added, then the pH is adjusted to 8.5 with a 0.1M NaOH solution, then 0.4 g of dopamine hydrochloride is added, and stirring is continued at room temperature for 16 h, the product is centrifuged with water and washed 3 times, and dried to obtain the CNP hybrid material;

[0029] S3: Preparation of CNP@CH hybrid material: 0.1 g of CNP is ultrasonically dispersed in 50 mL of deionized water, then transferred to a three-necked flask, the three-necked flask is placed in an oil bath at 60°C, stirring is continued at 60°C to form solution A, then 0.1 g of chitosan and 1 mL of acetic acid are dispersed in 100 mL of deionized water to form solution B, and solution B is added to solution A, and the reaction is carried out at 60°C for 6 h, the product is centrifuged with water and washed 3 times, and dried to obtain the CNP@CH hybrid material;

[0030] S4: Preparation of CNP@CH@Si hybrid material: 0.1g CNP@CH was ultrasonically dispersed in 150mL of deionized water, and then 1.5mL of silane coupling agent KH-560 was added dropwise at 60℃. The reaction was carried out at 60℃ for 4h. The product was centrifuged with water and washed 3 times. After drying, CNP@CH@Si hybrid material was obtained.

[0031] S5: Preparation of high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating: 98g of base material and 2g of CNP@CH@Si hybrid material are mixed and mechanically stirred for 5h to form a uniform dispersion system. The uniform dispersion system is then brushed onto the surface of the steel sheet. After brushing, it is cured at room temperature for 7 days to obtain the high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating.

[0032] This embodiment demonstrates the experimental analysis results related to the preparation method of the high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating proposed in this paper.

[0033] Waterborne intumescent fire retardant coatings CN / EP, CNP / EP, CNP@CH / EP, and CNP@CH@Si / EP were prepared using 2g of CN, CNP, CNP@CH, and CNP@CH@Si and 98g of base material, respectively. Pure epoxy resin (EP) was used as a control. The fire retardant coatings were applied to sandblasted steel sheets and cured at room temperature for 7 days to obtain test samples.

[0034] (1) The morphology of CN, CNP, CNP@CH and CNP@CH@Si nanohybrids was observed using a JEOL JEM-2100 high-resolution transmission electron microscope (HR-TEM). The results are shown in the appendix. Figure 1 .from Figure 1 As can be seen in A and E, CN has a rough lamellar structure; after modification with dopamine hydrochloride ( Figure 1 B and F) uniformly loaded a layer of polydopamine on the CN surface, indicating successful polydopamine loading; after loading chitosan ( Figure 1 C and G), a uniformly distributed polyhedral structure can be observed on the CN surface, indicating successful chitosan loading; after modification with silane coupling agent KH-560 ( Figure 1 The nanomaterials (D and H) are uniformly coated with a thin organic layer of silane coupling agent KH-560. These results demonstrate the successful synthesis of the CNP@CH@Si nanohybrid material.

[0035] (2) The cross-sectional morphology of each fire-retardant coating was observed using a JSM-7500F scanning electron microscope. The results are shown in the appendix. Figure 2 .from Figure 2 As can be seen from A, the cross-section of pure EP is relatively smooth. After adding graphitic carbon nitride ( Figure 2B), it was found that the fracture surface showed aggregation and cracks, which was caused by the poor dispersion of CN in the epoxy resin. After coating with polydopamine ( Figure 2 C), the dispersion of CNP was improved, and the aggregation was significantly reduced, but there were still a small amount of cracks, indicating that the compatibility of CNP with the epoxy resin was insufficient. After loading with chitosan on the surface ( Figure 2 D), the cracks disappeared, and CNP@CH dispersed well in the epoxy matrix. After further modification with silane coupling agent KH-560 ( Figure 2 E), CNP@CH@Si showed a typical wrinkle fracture surface, indicating that the interfacial interaction force of the epoxy resin was significantly enhanced, proving that the epoxy groups of silane coupling agent KH-560 effectively enhanced the interaction force between the nanohybrid material and the epoxy resin.

[0036] (3) The temperature of the back surface of the steel plate was tested by the large plate method to detect the fireproof performance of the fireproof coating. The results are shown in the attached Figure 3 . It can be seen from Figure 3 that the temperature of the back surface of the steel plate of the water-based intumescent fireproof coating containing CNP@CH@Si nanohybrid material is the lowest, which is reduced by 38.3% compared with pure EP, indicating that CNP@CH@Si can effectively improve the strength and flame retardancy of the carbon layer, increase the barrier to heat and volatile substances, and thus effectively slow down the rise of the temperature of the back surface of the steel plate, improving the fireproof performance.

[0037] (4) The intumescent behavior of the water-based intumescent fireproof coating was studied by furnace test, and the results are shown in the attached Figure 4 . It can be seen from Figure 4 that pure EP ( Figure 4 A) shows very low intumescent height and uneven intumescent. After adding fillers, the intumescent height increases. After adding CNP@CH, the intumescent height further increases, which is due to the fact that chitosan provides more abundant carbon source, increasing the quality and strength of the carbon layer, and making the intumescent more uniform when the gas blows up the carbon source. For CNP@CH@Si / EP, the intumescent is uniform and the intumescent height is the highest, which is increased by 331% compared with pure EP, indicating that the core-shell structure formed by chitosan and silane coupling agent KH-560 in CNP@CH@Si hybrid and the formation of silicon network effectively increase the strength of the carbon layer, further enhancing the intumescent performance, which is beneficial to blocking the propagation of flame and the invasion of flammable gas.

[0038] (5) The structure of the carbon layer after the large plate test was tested by JSM-7500F scanning electron microscope, and the results are shown in the attached Figure 5 . It can be seen from Figure 5 that cracks are found in the carbon layer of EP, CN / EP and CNP / EP. When CNP@CH ( Figure 5 D) and CNP@CH@Si ( Figure 5E) After the nanohybrid material, the cracks on the carbon layer disappear. The inner wall of the CNP@CH@Si / EP carbon layer is more dense and complete, and no cracks and holes are found, indicating that the quality of the carbon layer is further increased, because the formation of the silicon network further increases the strength of the carbon layer. These phenomena show that the physical barrier effect of the CNP@CH@Si nanosheet is beneficial to the improvement of the quality of the final carbon layer. The continuous and dense carbon layer is beneficial to resist heat transfer, delay mass loss, and inhibit the release of pyrolysis products, thereby improving the fireproof performance.

[0039] The preparation method of the high-temperature-resistant CNP@CH@Si steel structure intumescent fireproof coating provided by the application solves the dangerous characteristics of low carbon layer strength, uneven expansion and poor flame retardant performance of the current water-based fireproof coating, and the obtained water-based intumescent fireproof coating can form a uniform and high-strength intumescent carbon layer at high temperature, and the intumescent carbon layer has enhanced flame retardant performance and thermal stability, can effectively provide a barrier function to hinder the transmission of heat and combustible gas, and has a protective effect. The application is mainly used for steel structure fire protection, and forms an intumescent carbon layer to block the invasion of fire and delay the reaching of the steel structure failure temperature when a fire occurs, thereby prolonging the precious rescue time. The water-based intumescent fireproof coating has the advantages of easy availability of raw materials, simple preparation, low cost and environmental protection, and has wide industrial application value.

[0040] The above description does not limit the application in any form, although the application has been disclosed by the above examples, but not to limit the application, any skilled person in the art, without departing from the technical solution of the application, can utilize the disclosed technical content to make some changes or modifications as equivalent examples of equivalent changes, but as long as it does not deviate from the content of the technical solution of the application, according to the technical essence of the application, any simple modification, equivalent change and modification of the above examples are still within the scope of the technical solution of the application.

Claims

1. A method for preparing a high-temperature resistant CNP@CH@Si steel structure intumescent fire-retardant coating, characterized in that, Includes the following steps: S1: Preparation of base material: Weigh a certain amount of waterborne epoxy resin, curing agent, melamine polyphosphate, dipentaerythritol and melamine, stir at a rate of 300 r / min for 3 h, and then stir at a rate of 60 r / min for 2 h to obtain a uniformly mixed base material. S2: Preparation of CNP hybrid material: First, a certain amount of graphitic carbon nitride was ultrasonically dispersed in 200 mL of deionized water, then 0.32 g of Tris-HCl was added, and the pH was adjusted to 8.5 with 0.1 M NaOH solution. Then, a certain amount of dopamine hydrochloride was added, and the mixture was stirred at room temperature for 16 h. The product was centrifuged with water and washed 3 times. After drying, the CNP hybrid material was obtained. S3: Preparation of CNP@CH hybrid material: A certain amount of CNP hybrid material was ultrasonically dispersed in 50 mL of deionized water, and then transferred to a three-necked flask. The three-necked flask was placed in an oil bath at 60 °C and stirred continuously at 60 °C to form solution A. Then, a certain amount of chitosan and a certain amount of acetic acid were dispersed in 100 mL of deionized water to form solution B. Solution B was added to solution A and reacted at 60 °C for 6 h. The product was centrifuged with water and washed 3 times. After drying, CNP@CH hybrid material was obtained. S4: Preparation of CNP@CH@Si hybrid material: A certain amount of CNP@CH hybrid material was ultrasonically dispersed in 150 mL of deionized water, and then a certain amount of silane coupling agent KH-560 was added dropwise at 60 °C. The reaction was carried out at 60 °C for 4 h. The product was centrifuged with water and washed 3 times. After drying, CNP@CH@Si hybrid material was obtained. S5: Preparation of high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating: A certain amount of base material and a certain amount of CNP@CH@Si hybrid material are mixed and mechanically stirred for 5 hours to form a uniform dispersion system. The uniform dispersion system is then brushed onto the surface of the steel sheet. After brushing, it is cured at room temperature for 7 days to obtain the high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating.

2. The preparation method of a high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating as described in claim 1, characterized in that, In step S1, the mass ratio of waterborne epoxy resin, curing agent, melamine polyphosphate, dipentaerythritol, and melamine is 20:10:6:3:

1.

3. The preparation method of a high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating as described in claim 1, characterized in that, In step S2, the mass ratio of graphitic carbon nitride to dopamine hydrochloride is 1:4-6.

4. The preparation method of a high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating as described in claim 1, characterized in that, In step S3, the mass ratio of CNP hybrid material, chitosan, and acetic acid is 1:1-2:8-12.

5. The preparation method of a high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating as described in claim 1, characterized in that, In step S4, the mass ratio of CNP@CH hybrid material to silane coupling agent KH-560 is 1:10-20.

6. The preparation method of a high-temperature resistant CNP@CH@Si steel structure intumescent fireproof coating as described in claim 1, characterized in that, In step S5, the CNP@CH@Si hybrid material accounts for 1%-6% of the total weight of the uniformly dispersed system.

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