Ceramifiable fiber prepreg for building steel structure coating and preparation method thereof

Abstract

The application relates to a ceramicizable fiber prepreg for coating a building steel structure and a preparation method thereof, and belongs to the technical field of building protection. The ceramicizable fiber prepreg comprises a fiber reinforced material and a ceramicizable resin infiltrated in the fiber reinforced material; the ceramicizable resin comprises a resin matrix, a ceramicizable composition and a flame retardant; the ceramicizable composition comprises a ceramic precursor, an oxide powder, a porcelain-forming filler, a fluxing agent and modified boron-ene nanosheets; the ceramic precursor is one or more of polysiloxane, polysilsesquioxane, borosilicate sol and nanometer silicon dioxide sol; the oxide powder is aluminum oxide powder and / or zirconium dioxide powder; and the porcelain-forming filler is one or more of microsilica powder, kaolin, mica powder and talc powder. The ceramicizable fiber prepreg can be conveniently coated on the surface of the building steel structure, and has the functions of long-acting corrosion resistance, structure reinforcement and extreme fire protection.

Description

Technical Field

[0001] This invention belongs to the field of building protection technology, and in particular relates to a ceramicizable fiber prepreg for cladding steel structures and its preparation method. Background Technology

[0002] The fatal weakness of steel structure buildings is their rapid loss of strength at high temperatures. Typically, their yield strength drops by half at 500-600℃, leading to building collapse. Traditional fire protection solutions mainly include intumescent and non-intumescent fire-retardant coatings, fire-resistant board cladding, and flexible roll cladding. Intumescent coatings foam upon contact with fire, forming a heat-insulating char layer, but their durability is poor; they are prone to peeling and powdering in humid and corrosive environments, and may release toxic fumes during combustion. Non-intumescent coatings (such as thick fire-resistant mortar) are heavy, space-consuming, and detract from the building's aesthetics. Fire-resistant board cladding often uses inorganic materials such as gypsum board and calcium silicate board to wrap the steel structure. This method is complex to construct, and the joints can easily become weak points in fire protection. It also suffers from significant weight and space occupation. Flexible roll cladding often uses ceramic felt, rock wool, etc., requiring an external metal protective plate. The system is complex, and long-term use may result in settlement or damage, affecting the fire-resistant effect. In summary, traditional solutions are mostly "passive" physical insulation layers with limited functionality, and generally suffer from problems such as poor durability, complicated construction, high maintenance costs, or inability to provide structural contributions during fires.

[0003] Furthermore, steel structures in highly corrosive environments such as coastal areas, offshore locations, and chemical plants face severe corrosion conditions including chloride ions, high humidity, and salt spray, making protection a comprehensive challenge. Conventional methods employ heavy-duty anti-corrosion coating systems (such as epoxy zinc-rich primer, epoxy micaceous iron oxide intermediate paint, and polyurethane topcoat) to treat steel structure surfaces. However, these organic coatings themselves are not fire-resistant and will rapidly burn and fail in a fire. Existing comprehensive protection technologies typically involve a simple combination of "anti-corrosion coating + external fire protection," but the durability of fire-retardant coatings in corrosive environments is a weakness, and salt spray erosion significantly reduces their expansion performance and bonding strength. If fireproof board cladding systems are not properly sealed, corrosive media can penetrate the interlayer, accelerating the corrosion of the internal steel structure, which is difficult to detect. In short, currently, there is a lack of a material system that integrates long-term corrosion resistance and efficient active fire protection for steel structure systems in corrosion-resistant environments. Existing combined solutions suffer from poor interface compatibility and insufficient long-term reliability.

[0004] Fiber-reinforced polymer (FRP) composites have been widely used in building reinforcement and protection due to their high specific strength, excellent corrosion resistance, and design flexibility. For example, sheets / fabrics made of carbon fiber / epoxy resin or glass fiber / unsaturated polyester resin, bonded to the surface of a steel structure with adhesives, can effectively block corrosive media and improve the structural load-bearing capacity. However, the resin matrix is ​​usually flammable, posing a safety hazard in a fire. Conventional flame-retardant fireproofing technologies for composite materials mainly achieve flame retardancy or self-extinguishing by adding large amounts of flame retardants such as aluminum hydroxide and magnesium hydroxide. However, under extreme fire conditions, this "additive" flame retardant method still results in resin decomposition and loss of adhesion, causing the FRP layer to detach and failing to provide continuous protection for the steel structure. Furthermore, the resin decomposition process is usually accompanied by large amounts of smoke and toxic gases.

[0005] In summary, it is essential to provide a ceramicizable fiber prepreg for cladding steel structures and its preparation method. Summary of the Invention

[0006] To address one or more technical problems existing in the prior art, this invention provides a ceramicizable fiber prepreg for cladding steel structures and its preparation method. The ceramicizable fiber prepreg of this invention can be easily applied to the surface of steel structures, integrating long-term corrosion resistance, structural reinforcement, and extreme fire protection functions. It is particularly suitable for long-term protection of steel structures in harsh environments such as coastal cities, offshore platforms, and chemical workshops.

[0007] In a first aspect, this invention provides a ceramizable fiber prepreg for cladding steel structures, comprising a fiber reinforcing material and a ceramizable resin impregnated in the fiber reinforcing material; the ceramizable resin comprises a resin matrix, a ceramizable composition, and a flame retardant; the ceramizable composition comprises a ceramizable precursor, oxide powder, ceramic filler, flux, and modified boronene nanosheets; the ceramizable precursor is one or more selected from polysiloxane, polysilsesquioxane, borosilicate sol, and nano-silica sol; the oxide powder is alumina powder and / or zirconium dioxide powder; and the ceramic filler is microsilica powder, kaolin, and mica powder. One or more of talc powder; the preparation of the modified boronene nanosheets includes the following steps: (1) adding silane coupling agent to an ethanol aqueous solution and stirring evenly to obtain an ethanol aqueous solution of silane coupling agent, then adjusting the pH of the ethanol aqueous solution of silane coupling agent to 4~5 and performing pre-hydrolysis for 20~60 min to obtain an ethanol aqueous solution of pre-hydrolyzed silane coupling agent; (2) adding boronene nanosheets to the ethanol aqueous solution of pre-hydrolyzed silane coupling agent and performing ultrasonic treatment under inert gas protection to obtain a boronene nanosheet suspension; (3) stirring the boronene nanosheet suspension at 50~60℃ for 2~3 h under inert gas protection, and then separating, washing and drying to obtain modified boronene nanosheets.

[0008] Preferably, in the ceramizable resin, the mass of the modified boronene nanosheets is 0.5 to 3% of the mass of the resin matrix.

[0009] Preferably, in step (1), the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and / or the aqueous ethanol solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8~10):1.

[0010] Preferably, the raw materials for preparing the modified boronene nanosheets include boronene nanosheets, silane coupling agent and ethanol aqueous solution in a mass ratio of 1:(0.5~1):(50~80); and / or the ultrasonic treatment temperature is 30~40℃, the ultrasonic treatment power is 300~500W, and the ultrasonic treatment time is 60~90min.

[0011] Preferably, the fiber reinforcement material is basalt fiber reinforcement material; the resin matrix is ​​one or more of epoxy resin, phenolic resin, and vinyl ester resin; the flux is low-melting-point glass powder and / or zinc borate, wherein the low-melting-point glass powder is borosilicate glass powder and / or phosphate glass powder; the flame retardant is one or more of aluminum hydroxide, magnesium hydroxide, expanded graphite, and organophosphorus flame retardants; and / or the ceramizable resin further contains an initiator, an accelerator, and a toughening agent, wherein the initiator is methyl ethyl ketone peroxide, the accelerator is cobalt naphthenate and / or cobalt isooctanoate, and the toughening agent is carboxyl-terminated liquid nitrile rubber.

[0012] Preferably, the ceramicizable resin contained in the ceramicizable fiber prepreg for cladding building steel structures has a mass percentage content of 20-60 wt%; and / or in the ceramicizable resin, the mass of the ceramicizable precursor is 5-20% of the mass of the resin matrix, the mass of the oxide powder is 5-20% of the mass of the resin matrix, the mass of the ceramicizing filler is 2-10% of the mass of the resin matrix, the flux is 3-15% of the mass of the resin matrix, and the flame retardant is 10-25% of the mass of the resin matrix.

[0013] Preferably, the oxide powder comprises nano-oxide powder with a particle size of 20-200 nm and micro-oxide powder with a particle size of 1-5 μm in a mass ratio of (1.2-1.6):(1.8-2.5).

[0014] Preferably, the fiber reinforcing material is a fiber reinforcing material that has been surface modified with a silane coupling agent; the silane coupling agent is one or more of γ-glycidoxypropyltrimethoxysilane, N-(β-aminoethyl-γ-aminopropyl)trimethoxysilane, and γ-aminopropyltriethoxysilane.

[0015] Preferably, the preparation of fiber-reinforced material with silane coupling agent surface modification includes: preparing a silane coupling agent solution with a concentration of 1-5 wt% using an aqueous ethanol solution, adjusting the pH of the silane coupling agent solution to 4-10 and pre-hydrolyzing it for 20-60 min to obtain a pre-hydrolyzed silane coupling agent solution, then immersing the fiber-reinforced material in the pre-hydrolyzed silane coupling agent solution, and then heat-treating it to obtain the fiber-reinforced material with silane coupling agent surface modification.

[0016] Preferably, the soaking treatment is performed at room temperature for 5 to 30 minutes; the heat treatment is performed at a temperature of 80 to 120°C for 1 to 2 hours.

[0017] The present invention provides, in a second aspect, a method for preparing a ceramicizable fiber prepreg for cladding steel structures according to the first aspect of the present invention, the method comprising the following steps: (a) The fiber-reinforced material is impregnated in a ceramicizable resin to obtain the impregnated fiber-reinforced material; (b) The impregnated fiber-reinforced material is rolled and pre-dried to obtain a ceramicizable fiber prepreg for cladding of building steel structures.

[0018] Preferably, the immersion temperature is 40~55℃; the roller pressing pressure is 0.2~0.4MPa; the roller pressing linear speed is 0.3~0.6m / min; and / or the pre-drying temperature is 80~90℃, and the pre-drying time is 3~5min.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention is the first to propose a ceramicizable fiber prepreg for cladding steel structures in buildings. The ceramicizable fiber prepreg is preferably made of basalt fiber with excellent corrosion resistance as the reinforcing material and ceramicizable resin with improved design as the matrix. This invention integrates three functions of corrosion protection, structural reinforcement and active ceramic fire protection into a single prepreg material for the first time. In normal conditions, it can serve as a strong corrosion barrier and structural reinforcement layer, effectively resisting marine salt spray corrosion and improving structural stiffness through fiber reinforcement effect. In fire conditions, it can not only be highly flame-retardant and produce low smoke and low toxicity, but also transform into an in-situ generated ceramic protective shell. The ceramic protective shell has excellent heat insulation and structural integrity and can withstand the direct impact of high temperature flames on the steel structure of the building for a long time, winning crucial time for personnel evacuation and fire rescue. The ceramicizable fiber prepreg for cladding steel structures can achieve ultimate protection through the active evolution of its own properties.

[0020] (2) In this invention, the ceramicizable resin is used to optimize the composition and ratio of the ceramicizable composition in order to meet the building fire temperature curve (usually below 1100℃) and on-site construction requirements. By preferentially introducing low-melting-point glass powder, zinc borate and other fluxes, the starting temperature of the ceramicization reaction is significantly reduced (down to below 600℃), ensuring that a ceramic protective layer can be effectively formed before the steel structure reaches the critical temperature. At the same time, flame retardants are compounded in the ceramicizable resin, which helps to achieve flame retardancy and smoke suppression from the medium and low temperature zone to the ceramic zone in the high temperature zone. The molding process achieves a smooth transition and synergistic effect. More importantly, the ceramizable resin also contains modified boronene nanosheets. This invention has found that the use of modified boronene nanosheets can significantly improve the overall performance of ceramizable fiber prepregs used for cladding steel structures. This is likely because the modified boronene nanosheets, with their high specific surface area and excellent layered barrier effect, can effectively improve the interfacial bonding strength between the resin matrix and the fiber reinforcement after being uniformly dispersed in the resin matrix, thereby enhancing the mechanical properties and processing wettability of the prepreg and strengthening the curing of the ceramizable resin. The modified boronene nanosheets enhance structural stability and thermal shock resistance. During high-temperature ablation, they act as a char-forming promoter, catalyzing the cross-linking of the resin matrix to form a dense carbon layer. This carbon layer, combined with the ceramic phase generated by sintering the ceramizable composition, forms a composite structure where the carbon and ceramic layers synergistically reinforce each other, exhibiting both thermal insulation and flame retardancy, as well as high-temperature structural stability, while synergistically inhibiting heat transfer and oxygen permeation. In some preferred embodiments, by controlling the amount of modified boronene nanosheets added to 0.5-3% of the resin matrix mass, it is possible to achieve the desired structural stability and thermal shock resistance. This invention achieves synergistic optimization in terms of interfacial reinforcement and char formation promotion. It finds that if the amount of modified boronene nanosheets added is too low, it is difficult to fully utilize their interfacial reinforcement and char formation promotion effects, resulting in insignificant improvement in the overall performance of the prepreg. Conversely, if the amount of modified boronene nanosheets added is too high, it can lead to an increase in internal defects in the resin matrix, resulting in a decrease in interfacial bonding strength. Furthermore, it can introduce pore defects into the ceramic layer, damaging the density and integrity of the composite structure, which is detrimental to the thermal insulation and structural stability of the ceramicizable fiber prepreg used for cladding steel structures at high temperatures. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] In a first aspect, this invention provides a ceramizable fiber prepreg for cladding steel structures in buildings. The ceramizable fiber prepreg comprises a fiber reinforcing material and a ceramizable resin impregnated with the fiber reinforcing material. The ceramizable resin comprises a resin matrix, a ceramizable composition, and a flame retardant. The ceramizable composition comprises a ceramization precursor, oxide powder, ceramic filler, flux, and modified boronene nanosheets. The ceramization precursor is one or more of polysiloxane, polysilsesquioxane (POSS), borosilicate sol, and nano-silica sol. This invention does not specifically limit the types of polysiloxane, polysilsesquioxane (POSS), borosilicate sol, and nano-silica sol; for example, directly purchased products or products synthesized by existing methods can be used. In some specific applications… In the embodiments, the nano-silica sol used is a colloidal dispersion system (sol) formed by uniformly dispersing nano-sized silica particles in water as the dispersed phase. The average particle size of the nano-silica in the nano-silica sol is, for example, 20~50nm, and the solid content of the nano-silica sol is, for example, 25~30wt%. The oxide powder is alumina powder (Al2O3 powder) and / or zirconium dioxide powder (ZrO2 powder). The ceramic filler is one or more of microsilica powder (silica fume), kaolin, mica powder, and talc powder. The present invention does not specifically limit the particle size of microsilica powder, kaolin, mica powder, and talc powder. Those skilled in the art can conventionally select them. For example, the average particle size of microsilica powder is 0.1~0.3μm, and the average particle size of kaolin, mica powder, and / or talc powder is 5~15μm.

[0023] In this invention, the preparation of the modified boronene nanosheets includes the following steps: (1) Add silane coupling agent to ethanol aqueous solution and stir evenly to obtain ethanol aqueous solution of silane coupling agent. Then adjust the pH of ethanol aqueous solution of silane coupling agent to 4~5 and perform pre-hydrolysis for 20~60min to obtain ethanol aqueous solution of pre-hydrolyzed silane coupling agent. In step (1) of this invention, acetic acid is used to adjust the pH of ethanol aqueous solution of silane coupling agent to 4~5. This invention does not make specific limitations on the amount of acetic acid used, as long as the pH of ethanol aqueous solution of silane coupling agent is adjusted to the target range. (2) Add boronene nanosheets to the ethanol aqueous solution of the pre-hydrolyzed silane coupling agent and sonicate under the protection of an inert gas (such as nitrogen or argon) to obtain a boronene nanosheet suspension. (3) The boronene nanosheet suspension is stirred at 50-60°C for 2-3 hours under the protection of an inert gas (such as nitrogen or argon), and then separated, washed and dried to obtain modified boronene nanosheets; In this invention, for example, the suspension system obtained after stirring for 2-3 hours is centrifuged at 6000-10000 rpm for 10-20 minutes under the protection of an inert gas (such as nitrogen or argon), the supernatant is discarded, the precipitate is collected, anhydrous ethanol is added to the precipitate and centrifuged and washed 3 times under the protection of an inert gas (such as nitrogen or argon), and finally the washed precipitate is placed in a vacuum drying oven and vacuum dried at 50°C to constant weight to obtain the modified boronene nanosheets.

[0024] This invention innovatively proposes a ceramicizable fiber prepreg for cladding steel structures. The preferred ceramicizable fiber prepreg uses basalt fiber with excellent corrosion resistance as the reinforcing material and a modified ceramicizable resin as the matrix. This invention integrates corrosion protection, structural reinforcement, and active ceramicizing fire protection into a single prepreg material for the first time. Under normal conditions, it serves as a robust corrosion-resistant barrier and structural reinforcement layer, effectively resisting marine salt spray corrosion and improving structural stiffness through fiber reinforcement. In a fire, it not only provides highly efficient flame retardancy and low smoke and toxicity, but also transforms into an in-situ generated ceramic protective shell. This ceramic protective shell possesses excellent thermal insulation and structural integrity, capable of withstanding the direct impact of high-temperature flames on the steel structure for extended periods, buying crucial time for personnel evacuation and fire rescue. This ceramicizable fiber prepreg for cladding steel structures achieves ultimate protection through the active evolution of its own properties.

[0025] This invention utilizes a ceramizable resin, specifically targeting building fire temperature curves (typically below 1100℃) and on-site construction requirements. The composition and ratio of the ceramizable composition are innovatively optimized within the resin. By preferentially introducing low-melting-point glass powder and zinc borate as fluxes, the onset temperature of the ceramization reaction is significantly reduced (down to below 600℃), ensuring effective formation of a ceramic protective layer before the steel structure reaches its critical temperature. Simultaneously, the addition of flame retardants to the ceramizable resin facilitates a smooth transition and synergistic effect from flame retardancy and smoke suppression in the low-to-medium temperature range to ceramic forming in the high-temperature range. More importantly, the ceramizable resin also contains modified boronene nanosheets. This invention reveals that the use of these modified boronene nanosheets can significantly improve the cladding of building steel structures. The superior comprehensive performance of ceramizable fiber prepregs is likely due to the fact that modified boronene nanosheets, with their high specific surface area and excellent layered barrier effect, can effectively improve the interfacial bonding strength between the resin matrix and the fiber reinforcement after uniform dispersion in the resin matrix. This enhances the mechanical properties and processing wettability of the prepreg, and strengthens the structural stability and thermal shock resistance of the ceramizable resin after curing. During high-temperature ablation, modified boronene nanosheets can act as a char-forming promoter, for example, catalyzing the cross-linking of the resin matrix into char to form a dense char layer. This char layer, combined with the ceramic phase generated by sintering the ceramizable composition, forms a composite structure with synergistic reinforcement of the char and ceramic layers, possessing both heat insulation and flame retardancy as well as high-temperature structural stability, synergistically inhibiting heat transfer and oxygen permeation. The ceramizable fiber prepreg for cladding steel structures in this invention solves the problem of easy failure and detachment of traditional composite fireproof cladding layers at high temperatures, achieving active protection that becomes "stronger the longer it burns" during a fire.

[0026] According to some preferred embodiments, the mass of the modified boronene nanosheets is 0.5-3% of the mass of the resin matrix, preferably 1-2%. In this invention, it is preferred that by controlling the amount of modified boronene nanosheets added to 0.5-3% of the mass of the resin matrix, synergistic optimization can be achieved in terms of interface reinforcement and char formation promotion. This invention has found that if the amount of modified boronene nanosheets added is too low, it is difficult to fully exert its interface reinforcement and char formation promotion effects, and the effect on improving the overall performance of the prepreg is not significant. If the amount of modified boronene nanosheets added is too high, it will lead to an increase in defects inside the resin matrix, resulting in a decrease in interfacial bonding force, and will also introduce pore defects inside the ceramic layer, destroying the compactness and integrity of the composite structure, which is detrimental to the thermal insulation and structural stability of the ceramicizable fiber prepreg at high temperatures.

[0027] According to some preferred embodiments, in step (1), the silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560), and / or the ethanol aqueous solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8~10):1; the raw materials for preparing the modified boronene nanosheets include boronene nanosheets, silane coupling agent and ethanol aqueous solution in a mass ratio of 1:(0.5~1):(50~80); and / or the temperature of the ultrasonic treatment is 30~40℃, the power of the ultrasonic treatment is 300~500W, and the time of the ultrasonic treatment is 60~90min.

[0028] According to some preferred embodiments, the modified boronene nanosheets are prepared using raw materials comprising boronene nanosheets in a mass ratio of 1:(0.5~1):(50~80), a silane coupling agent (KH-560), and an aqueous ethanol solution (ethanol to water volume ratio of 9:1). A specific preparation method is as follows: silane coupling agent (KH-560) is added to the aqueous ethanol solution and stirred until homogeneous to obtain an aqueous ethanol solution of the silane coupling agent. Then, acetic acid is added to the aqueous ethanol solution of the silane coupling agent to adjust the pH to 4~5 while stirring (at a speed of 30 rpm). Pre-hydrolysis was performed for 20-60 min under 0-400 rpm conditions to obtain an ethanol-water solution of the pre-hydrolyzed silane coupling agent. Boronene nanosheets were then added to the ethanol-water solution of the pre-hydrolyzed silane coupling agent, and ultrasonically treated at 30-40°C and 300-500 W for 60-90 min under argon protection to obtain a uniform suspension of boronene nanosheets. The boronene nanosheet suspension was then stirred at 50-60°C (300-400 rpm) under argon protection for 2-3 h. Afterward, the stirred solution was... The suspension system obtained after ~3 hours was centrifuged at 6000~10000 rpm for 10~20 min under argon protection. The supernatant was discarded, and the precipitate was collected. Anhydrous ethanol was added to the precipitate and centrifuged and washed three times under argon protection. Finally, the washed precipitate was placed in a vacuum drying oven and vacuum dried at 50℃ to constant weight to obtain the modified boronene nanosheets. Compared with unmodified boronene nanosheets, the modified boronene nanosheets are more uniformly dispersed in the resin matrix and have stronger interfacial bonding, which can significantly improve the performance of steel structure cladding in buildings. The invention provides comprehensive performance of ceramicizable fiber prepregs. It does not specifically limit the type of boronene nanosheets used in preparing the modified boronene nanosheets; commercially available products or those prepared using existing methods are acceptable. In this invention, the boronene nanosheets can be prepared, for example, by referring to the method in Chinese Patent CN112758950B. The average sheet diameter of the boronene nanosheets is, for example, 0.05~10 μm, preferably 1~5 μm, and the average thickness is, for example, 0.8~20 nm, preferably 4~13 nm.

[0029] According to some preferred embodiments, the fiber reinforcement material is basalt fiber reinforcement material. In this invention, it is preferred that the fiber reinforcement material be basalt fiber reinforcement material. Basalt fiber itself has excellent corrosion resistance, high temperature resistance, non-combustibility, and good resin wettability, allowing it to act as a skeleton for ceramic bodies in fires, avoiding problems such as oxidation of carbon fibers or softening of glass fibers. It is an ideal reinforcement for steel structures, such as coastal steel structures. In this invention, the basalt fiber reinforcement material can be, for example, basalt fiber fabric, basalt fiber unidirectional cloth, or chopped basalt fiber felt. This invention does not specifically limit the choice of basalt fiber fabric, basalt fiber unidirectional cloth, or chopped basalt fiber felt; those skilled in the art can make conventional choices. Of course, in this invention, other inorganic fibers, glass fibers, carbon fibers, etc., can also be used as the fiber reinforcement material.

[0030] According to some preferred embodiments, the resin matrix is ​​one or more of epoxy resin, phenolic resin, and vinyl ester resin (e.g., bisphenol A type epoxy vinyl ester resin); in this invention, the resin matrix is ​​preferably a thermosetting resin such as epoxy resin, phenolic resin, or vinyl ester resin that has good adhesion, mechanical properties, and chemical corrosion resistance; the flux is low-melting-point glass powder and / or zinc borate, wherein the low-melting-point glass powder is borosilicate glass powder and / or phosphate glass powder. This invention does not particularly limit the use of borosilicate glass powder and / or phosphate glass powder, but preferably, borosilicate glass powder and / or phosphate glass powder with a softening point of 400~750℃ is selected; in some specific embodiments, the borosilicate glass powder can be, for example, borosilicate glass powder B-3033 or D245; in this invention, low-melting-point glass powder (e.g., low-melting-point epoxy vinyl ester resin) is preferred. Borosilicate glass powder (with a melting point of 400-750℃) is used as a flux to lower the starting temperature of the ceramization reaction, enabling effective sintering within the range of 600-900℃ and promoting ceramization. In this invention, the particle size (average particle size) of the borosilicate glass powder is, for example, 5-20 μm. And / or the flame retardant is one or more of aluminum hydroxide, magnesium hydroxide, expanded graphite, and organophosphorus flame retardants. In this invention, the average particle size of the aluminum hydroxide and / or magnesium hydroxide is, for example, 1-5 μm, and the average particle size of the expanded graphite is, for example, 100-300 μm. In this invention, the flame retardant is preferably aluminum hydroxide and / or magnesium hydroxide, which decomposes endothermally at 200-400℃, providing flame retardancy and smoke suppression. Its decomposition products (Al2O3 and / or MgO) can further participate in the ceramization reaction at high temperatures.

[0031] According to some preferred embodiments, the ceramizable resin further includes an initiator, an accelerator, and a toughening agent. The initiator is methyl ethyl ketone peroxide, the accelerator is cobalt naphthenate and / or cobalt isooctanoate, and the toughening agent is carboxyl-terminated liquid nitrile butadiene rubber (CTBN). In this invention, preferably, the resin matrix is ​​a vinyl ester resin. Adding the initiator methyl ethyl ketone peroxide and the accelerator cobalt naphthenate or cobalt isooctanoate facilitates the initiation and acceleration of the ceramizable resin reaction at room temperature or low temperature, enabling the material to cure and mold rapidly, satisfying the desired properties. The process meets the requirements of the construction site; the addition of toughening agent-terminated carboxyl liquid nitrile rubber is beneficial to the formation of a microphase separation structure after the ceramicizable resin is cured, which effectively absorbs impact energy, significantly improves the toughness and crack resistance of the material, and prevents the protective layer from failing due to brittle fracture; in this invention, the amount of the initiator is, for example, 1.5~2% of the mass of the resin matrix, the amount of the accelerator is, for example, 0.3~0.6% of the mass of the resin matrix; the amount of the toughening agent is, for example, 0.5~5% of the mass of the resin matrix, preferably 2~5%.

[0032] According to some preferred embodiments, the ceramicizable resin contained in the ceramicizable fiber prepreg for cladding steel structures is 20-60 wt%, preferably 25-50 wt%, which ensures that the ceramicizable fiber prepreg for cladding steel structures has good flexibility and adhesion, and can generate a ceramic body with sufficient strength at high temperatures; and / or in the ceramicizable resin, the mass of the ceramicization precursor is 5-20% of the mass of the resin matrix, and the mass of the oxide powder is... The resin matrix comprises 5-20% of its mass, the ceramic filler comprises 2-10% of its mass, the flux comprises 3-15% of its mass, and the flame retardant comprises 10-25% of its mass. In this invention, when the flame retardant is composed of aluminum hydroxide and / or magnesium hydroxide, expanded graphite, and organophosphorus flame retardant, the mass ratio of the organophosphorus flame retardant, expanded graphite, to aluminum hydroxide and / or magnesium hydroxide can be, for example, (3-15):(1-8):(5-20).

[0033] According to some preferred embodiments, the oxide powder comprises nano-oxide powder with a particle size of 20-200 nm and micro-oxide powder with a particle size of 1-5 μm in a mass ratio of (1.2-1.6):(1.8-2.5); in this invention, preferably, the oxide powder comprises nano-oxide powder with a particle size of 20-200 nm (preferably 20-80 nm) and micro-oxide powder with a particle size of 1-5 μm in a mass ratio of (1.2-1.6):(1.8-2.5). This invention has found that this specific ratio and particle size combination has a synergistic optimization effect on the ceramicization transformation process of the ceramicizable fiber prepreg for cladding building steel structures at high temperatures. A possible reason is that... During high-temperature sintering, nanoscale oxide powders, due to their high specific surface area and surface activity, preferentially undergo sintering and synergistically interact with active components in the system to effectively fill the voids between micron-sized particles, promoting the formation of a dense sintering neck and a continuous ceramic network skeleton, thereby improving the density of the initial ceramic body. Meanwhile, the micron-sized oxide powders act as a skeleton, sharing structural support with other powders, providing basic structural strength and dimensional stability for the ceramic layer and preventing cracking caused by excessive shrinkage. This enables the ceramicizable fiber prepreg for cladding building steel structures to form a dense and tough ceramic body at high temperatures, thus providing more durable and reliable high-temperature structural support for building steel structures during fires.

[0034] According to some preferred embodiments, the fiber reinforcement material is a fiber reinforcement material that has been surface modified with a silane coupling agent; the silane coupling agent is one or more of γ-glycidoxypropyltrimethoxysilane (KH-560), N-(β-aminoethyl-γ-aminopropyl)trimethoxysilane (KH-792), and γ-aminopropyltriethoxysilane (KH-550).

[0035] In this invention, preferably, the fiber reinforcement material is a material surface-modified with silane coupling agents KH-560, KH-792 and / or KH-550. This treatment can significantly improve the interfacial bonding performance between the fiber reinforcement material and the resin matrix, thereby giving the ceramicizable fiber prepreg for cladding steel structures a superior comprehensive protective capability. The possible reason is that the silane coupling agent can chemically react with the hydroxyl groups on the surface of the fiber (e.g., basalt fiber) to form covalent bonds, thereby introducing organic functional groups such as epoxy groups and / or amino groups on the fiber surface. This can significantly improve the wettability and compatibility between the fiber reinforcement material surface and the resin matrix, reduce interfacial tension, promote the uniform spreading and penetration of resin on the fiber surface, and enhance the interfacial bonding strength. This strengthened interfacial bonding not only enables the ceramicizable fiber prepreg for cladding steel structures to more effectively transfer loads in normal environments and exert the reinforcing effect of the fiber to improve structural stiffness, but also prevents interfacial debonding in high-temperature environments such as fires, ensuring that the fiber reinforcement material can still serve as a stable support for the ceramic layer after resin decomposition.

[0036] According to some preferred embodiments, the preparation of fiber-reinforced materials with silane coupling agent surface modification includes: preparing a 1-5 wt% silane coupling agent solution using an aqueous ethanol solution; adjusting the pH of the silane coupling agent solution to 4-10 and pre-hydrolyzing it for 20-60 min to obtain a pre-hydrolyzed silane coupling agent solution; immersing the fiber-reinforced material in the pre-hydrolyzed silane coupling agent solution; and then heat-treating it to obtain the fiber-reinforced material with silane coupling agent surface modification; the immersion treatment is, for example, immersion at room temperature for 5-30 min; the heat treatment temperature is 80-120°C, and the time is 1-2 h; in preparing the fiber-reinforced material with silane coupling agent surface modification, acetic acid or ammonia is used, for example, to adjust the silane... The pH of the coupling agent solution is 4-10. When the silane coupling agent used is γ-glycidoxypropyltrimethoxysilane (KH-560), acetic acid can be used to adjust the pH of the silane coupling agent solution to 4-5. This invention does not specify the amount of acetic acid used, as long as the pH of the silane coupling agent solution is adjusted to the target range. When the silane coupling agent used is N-(β-aminoethyl-γ-aminopropyl)trimethoxysilane (KH-792) and / or γ-aminopropyltriethoxysilane (KH-550), ammonia can be used to adjust the pH of the silane coupling agent solution to 9-10. This invention does not specify the concentration and amount of ammonia used, as long as the pH of the silane coupling agent solution is adjusted to the target range.

[0037] The present invention provides a second aspect of a method for preparing the ceramicizable fiber prepreg for cladding building steel structures as described in the first aspect, the method comprising the following steps: (a) Impregnating the fiber-reinforcing material in a ceramicizable resin to obtain the impregnated fiber-reinforcing material; (b) Rolling and pre-drying the impregnated fiber-reinforcing material to obtain a ceramicizable fiber prepreg for cladding steel structures; In this invention, the ceramicizable resin content in the ceramicizable fiber prepreg for cladding steel structures is 20-60 wt%, preferably 25-50 wt%; The ceramicizable fiber prepreg for cladding steel structures obtained by this invention can be stored in a cold storage at around -18°C for a shelf life of several weeks to several months.

[0038] According to some specific embodiments, the preparation of the ceramizable resin in step (a) is as follows: Vinyl ester resin (SW-901, Shangwei) is heated to 45°C to reduce viscosity; microsilica powder, talc powder, borosilicate glass powder, and alumina powder are added sequentially; the mixture is stirred for 30-45 minutes at a stirring speed of 800-1200 rpm; then magnesium hydroxide, expanded graphite, and nano-silica sol (nano-SiO2 sol) are added, and the mixture is stirred at a stirring speed of 600-800 rpm. Stir for 15-25 minutes; then add modified boronene nanosheets and stir at 400-600 rpm for 15-25 minutes. Next, add the initiator (methyl ethyl ketone peroxide), accelerator (cobalt isooctanoate), and toughening agent (CTBN), and continue stirring at 400-600 rpm for 10-15 minutes. Then, perform vacuum degassing at a vacuum degree of -0.1 to -0.08 MPa for 15-25 minutes to obtain a ceramicizable resin. The composition of the resin is as follows: the mass of the nano-SiO2 sol is 5-20% of the mass of the vinyl ester resin; the mass of the alumina powder is 5-20% of the mass of the vinyl ester resin; the sum of the masses of the microsilica powder, mica powder, and talc powder is 2-10% of the mass of the vinyl ester resin, and the mass ratio of the microsilica powder, mica powder, and talc powder is (40-55):(25-35):(10-25); the mass of the borosilicate glass powder is 3-15% of the mass of the vinyl ester resin; the sum of the masses of the magnesium hydroxide and expanded graphite is 10-25% of the mass of the vinyl ester resin, and the mass ratio of the magnesium hydroxide and expanded graphite is (40-80):(5-15); the mass of the methyl ethyl ketone peroxide is 1.5-2% of the mass of the vinyl ester resin; the mass of the cobalt isooctanoate is 0.3-0.6% of the mass of the vinyl ester resin; and the mass of the carboxyl-terminated liquid nitrile butadiene rubber (CTBN) is 2-5% of the mass of the vinyl ester resin.

[0039] According to some preferred embodiments, the impregnation temperature is 20~80℃, preferably 40~55℃; the present invention does not specifically limit the impregnation time, so that the fiber reinforcement material is fully impregnated, and finally the ceramicizable resin content in the ceramicizable fiber prepreg for building steel structure cladding is 20~60wt% after rolling and pre-drying. In some specific embodiments, the impregnation time is, for example, 3~5min; the rolling pressure is 0.2~0.4MPa; the rolling linear speed is 0.3~0.6m / min; and / or the pre-drying temperature is 80~90℃, and the pre-drying time is 3~5min.

[0040] According to some specific implementation methods, the fiber reinforcement material used is basalt fiber unidirectional fabric with an areal density of 240~300 g / m². 2 The fiber reinforcement material is a fiber reinforcement material surface-modified with a silane coupling agent. The preparation method is as follows: A silane coupling agent solution with a concentration of 1-5 wt% is prepared using an ethanol-water solution (the ethanol-water solution is a mixture of anhydrous ethanol and water in a volume ratio of (8-10):1). The pH of the silane coupling agent solution is then adjusted to 4-10 and pre-hydrolyzed for 20-60 minutes to obtain a pre-hydrolyzed silane coupling agent solution. The fiber reinforcement material (basalt fiber unidirectional fabric) is then immersed in the pre-hydrolyzed silane coupling agent solution, followed by heat treatment to obtain the fiber reinforcement material surface-modified with the silane coupling agent. The immersion treatment is carried out in a room... The fiber-reinforced material is immersed in a heat treatment at a temperature (e.g., room temperature 15~35℃) for 5~30 minutes; the heat treatment temperature is 80~120℃ and the time is 1~2 hours; then the obtained fiber-reinforced material with surface modification by silane coupling agent is impregnated in a ceramicizable resin at a temperature of 40~55℃, and then the resin is semi-cured by sequential rolling and pre-drying to obtain a ceramicizable fiber prepreg for cladding of building steel structures, which is easy to stack and store; wherein, the rolling pressure is 0.2~0.4MPa; the rolling linear speed is 0.3~0.6m / min; the pre-drying temperature is 80~90℃ and the pre-drying time is 3~5 minutes.

[0041] In some specific embodiments, the ceramizable fiber prepreg for cladding steel structures prepared according to the present invention is laminated with the steel structure by lamination and / or compression molding. For example, the compression molding temperature is 40~120℃, the compression molding time is 2~120min, and the compression molding pressure is 0.1~3.0MPa. In other specific embodiments, the ceramizable fiber prepreg for cladding steel structures prepared according to the present invention can also be applied to the steel structure on-site by hand lay-up and / or chopped strand spraying. For steel structure composites, after on-site hand lay-up and lamination, accelerate curing at room temperature (e.g., 15~35℃) or low temperature (60~80℃) for 10~60 minutes. Subsequently, perform segmented pre-ceramization in the workshop or a dedicated furnace. If whole-furnace treatment is not possible, use a local heating hood for surface pre-ceramization. For the resin matrix of the ceramicizable fiber prepreg for steel structure cladding used in hand lay-up / chopped strand spraying, prioritize low viscosity and short curing time formulations to maintain the process window. Spraying temperature, for example, 20~40℃, and spraying rate adjusted according to equipment specifications.

[0042] According to some specific embodiments, when the ceramicizable fiber prepreg for cladding building steel structures is used for cladding building steel structures, the present invention includes, for example: surface treatment: rust removal, cleaning, and drying of the surface of the building steel structure to be protected; lay-up: cutting the ceramicizable fiber prepreg for cladding building steel structures according to the design and directly pasting (laying) it onto the surface of the building steel structure; compaction can be performed using hand lay-up molding and / or vacuum bag pressing processes to eliminate interlayer air bubbles and ensure that the ceramicizable fiber prepreg for cladding building steel structures is tightly bonded to the building steel structure; for complex components, simple tooling can be used for auxiliary shaping; curing: under ambient temperature or moderate heating (such as 60~80℃), the resin in the prepreg is cross-linked and cured to form a composite material protective layer that is firmly bonded to the building steel structure.

[0043] To improve protection efficiency and save costs, multiple layers of different prepregs can be used to composite-encapsulate the steel structure of the building: for example, the inner layer (close to the steel structure) uses a prepreg containing fiber reinforcement materials and a resin matrix (without ceramizable compositions and flame retardants) impregnated in the fiber reinforcement materials, which has strong adhesion to the steel, is resistant to salt spray, and forms a corrosion-resistant shielding layer; the middle layer uses a ceramizable fiber prepreg for cladding the steel structure with a high content of ceramizable compositions, whose main function is to form a robust ceramic protective shell at extreme high temperatures; the outer layer uses a ceramizable fiber prepreg for cladding the steel structure with a high content of flame retardants, whose main function is to provide excellent flame retardant, heat insulation, and smoke suppression effects in the early stages of a fire, protect the inner layer, and delay the transfer of heat inward. When applied, this invention employs a functional gradient coating method that enables the optimal spatial distribution of the properties of the ceramicizable fiber prepreg used for cladding building steel structures. The outer layer focuses on flame retardancy, while the middle layer focuses on ceramicization. This division of labor and cooperation mechanism is more efficient and economical than a single homogeneous material, and can provide more durable all-round protection.

[0044] The present invention also provides a building steel structure product with corrosion resistance and fire resistance, the building steel structure product comprising a building steel structure and a ceramicizable fiber prepreg for cladding the building steel structure and covering the surface of the building steel structure, the ceramicizable fiber prepreg for cladding the building steel structure being the ceramicizable fiber prepreg for cladding the building steel structure described in the first aspect of the present invention or the ceramicizable fiber prepreg for cladding the building steel structure prepared by the preparation method described in the second aspect of the present invention.

[0045] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments. The present invention may have many other embodiments, and those skilled in the art can make various corresponding changes and modifications based on the present invention without departing from its spirit and essence. However, all such corresponding changes and modifications should fall within the scope of protection of the appended claims. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments can be obtained commercially or by existing methods.

[0046] The modified boronene nanosheets involved in the following embodiments are all the same. The raw materials used in their preparation include boronene nanosheets in a mass ratio of 1:0.6:70, silane coupling agent (KH-560), and an aqueous ethanol solution (ethanol to water volume ratio of 9:1). The preparation method is as follows: silane coupling agent (KH-560) is added to the aqueous ethanol solution and stirred (350 rpm) until homogeneous to obtain an aqueous ethanol solution of silane coupling agent. Then, acetic acid is added to the aqueous ethanol solution of silane coupling agent to adjust the pH to 4.5, and pre-hydrolyzing is performed for 30 min under stirring (350 rpm) to obtain an aqueous ethanol solution of pre-hydrolyzed silane coupling agent. Subsequently, the pre-hydrolyzed silane coupling agent... Boronene nanosheets were added to an ethanol-water solution and ultrasonically treated at 35°C with an ultrasonic power of 400W for 80 min under argon protection to obtain a uniform suspension of boronene nanosheets. The suspension was then stirred at 60°C (350 rpm) for 2.5 h under argon protection. After stirring for 2.5 h, the resulting suspension was centrifuged at 8000 rpm for 15 min under argon protection. The supernatant was discarded, and the precipitate was collected. Anhydrous ethanol was added to the precipitate, and the mixture was centrifuged and washed three times under argon protection. Finally, the washed precipitate was placed in a vacuum drying oven and vacuum dried at 50°C to constant weight to obtain modified boronene nanosheets.

[0047] Example 1 ① Formulation of ceramizable resin: Vinyl ester resin (SW-901, Shangwei) was heated to 45℃ to reduce viscosity. Microsilica powder (average particle size 0.2μm), mica powder (average particle size 15μm), talc powder (average particle size 10μm), borosilicate glass powder D245 (average particle size 10μm), and alumina powder (a mixture of nano alumina powder with an average particle size of 50nm and micro alumina powder with an average particle size of 3μm in a mass ratio of 1.5:2) were added sequentially. The mixture was stirred at 1000rpm for 40min. Then, magnesium hydroxide (average particle size 3 μm), expanded graphite (average particle size 150 μm), and nano-SiO2 sol (solid content 28 wt%, containing nano-SiO2 with a particle size distribution of 20-50 nm) were added and stirred at 700 rpm for 20 min. Modified boronene nanosheets were then added and stirred at 500 rpm for 20 min. Following this, an initiator (methyl ethyl ketone peroxide), an accelerator (cobalt isooctanoate), and a toughening agent (carboxyl-terminated liquid nitrile butadiene rubber CTBN) were added and stirred at 400 rpm. After stirring for 15 minutes at a constant temperature (m), vacuum degassing was performed at a vacuum degree of -0.08 MPa for 20 minutes to obtain a ceramicizable resin. The mass of the nano-SiO2 sol was 8% of the mass of the vinyl ester resin, the mass of the alumina powder was 10% of the mass of the vinyl ester resin, the total mass of the silica powder, mica powder, and talc powder was 6% of the mass of the vinyl ester resin, and the mass ratio of silica powder, mica powder, and talc powder was 4:3:2, the mass of the borosilicate glass powder was 5% of the mass of the vinyl ester resin, the total mass of the magnesium hydroxide and expanded graphite was 20% of the mass of the vinyl ester resin, and the mass ratio of magnesium hydroxide and expanded graphite was 4:1, the mass of the modified boronene nanosheets was 1.5% of the mass of the vinyl ester resin, the mass of the methyl ethyl ketone peroxide was 1.8% of the mass of the vinyl ester resin, the mass of the cobalt isooctanoate was 0.4% of the mass of the vinyl ester resin, and the mass of the carboxyl-terminated liquid nitrile rubber was 3% of the mass of the vinyl ester resin.

[0048] ② Preparation of fiber-reinforced materials with surface modification by silane coupling agent: A 2wt% silane coupling agent solution (KH-560) was prepared using an ethanol-water solution (the ethanol-water solution was prepared by mixing anhydrous ethanol and water in a volume ratio of 9:1). The pH of the silane coupling agent solution was then adjusted to 4.5 with acetic acid and pre-hydrolyzed for 30 minutes to obtain a pre-hydrolyzed silane coupling agent solution. This pre-hydrolyzed silane coupling agent solution was then used to coat basalt fiber unidirectional fabric (area density of 280 g / m²). 2The material is subjected to immersion treatment followed by heat treatment to obtain fiber-reinforced material with surface modification by silane coupling agent; the immersion treatment is performed at room temperature for 20 minutes; the heat treatment is performed at 100°C for 1.5 hours.

[0049] ③ Preparation of ceramicizable fiber prepreg for steel structure cladding: The obtained fiber reinforcement material, which has been surface modified with silane coupling agent, is impregnated in ceramicizable resin at a temperature of 40°C for 4 minutes to obtain the impregnated fiber reinforcement material; then, the impregnated fiber reinforcement material is sequentially rolled and pre-dried to achieve a semi-cured state of the resin, thus obtaining the ceramicizable fiber prepreg for steel structure cladding; wherein, the rolling pressure is 0.3 MPa; the rolling linear speed is 0.5 m / min; the pre-drying temperature is 85°C; and the pre-drying time is 4 minutes; the ceramicizable resin content in the ceramicizable fiber prepreg for steel structure cladding obtained in this embodiment is 50 wt%.

[0050] This embodiment also applies the ceramicizable fiber prepreg for cladding steel structures using a combination of manual lay-up and vacuum bag pressing: First, the steel structure is derusted, cleaned, and dried; then, the ceramicizable fiber prepreg for cladding steel structures is cut according to the design and directly pasted (laid) onto the surface of the steel structure by hand lay-up, with a thickness of 3mm; after the hand lay-up, a release film and breathable felt are laid on top, and the structure is sealed in a vacuum bag. The vacuum is then drawn until the vacuum degree inside the vacuum bag is -0.08MPa, and then heated and cured at 80℃ for 60 minutes. This construction method has a moderate curing temperature and is easy to operate, making it suitable for scenarios such as offshore platform maintenance that require rapid construction.

[0051] The coating performance test results of the ceramicizable fiber prepreg for cladding building steel structures prepared in Example 1 of this invention are shown in Table 1.

[0052] Table 1 In Table 1, the traditional fire-retardant coating sample for steel structures, serving as control A, was prepared according to the technical requirements for fire-retardant coatings for steel structures specified in the national standard GB 14907-2018 "Fire-retardant Coatings for Steel Structures." It was formulated using a commercially available general-purpose water-based epoxy emulsion and an ammonium polyphosphate-pentaerythritol-melamine intumescent flame-retardant system. A 3mm thick coating was applied to the steel structure surface using a spraying process and allowed to cure naturally for 14 days until completely dry before performance testing. The ordinary glass fiber / vinyl ester resin coated sample, serving as control B, had a surface density of 280 g / m³. 2Alkali-free unidirectional glass fiber fabric was used as the fiber reinforcement material, and Shangwei SW-901 vinyl ester resin was used as the resin matrix. Methyl ethyl ketone peroxide (MEK) was added at a rate of 1.8% of the resin matrix mass as an initiator and cobalt isooctanoate (COA) at a rate of 0.4% of the resin matrix mass as an accelerator. The glass fiber reinforced composite material layer with a thickness of 3 mm was formed on the surface of the steel structure through manual lay-up and vacuum bag pressing processes. After curing at 80℃ for 60 min and then at room temperature for 24 h, it was used for performance testing. In Table 1, " / " indicates that this performance index was not tested.

[0053] Example 2 Example 2 is basically the same as Example 1, except that: The mass of the modified boronene nanosheets is 0.5% of the mass of the vinyl ester resin.

[0054] Example 3 Example 3 is basically the same as Example 1, except that: The mass of the modified boronene nanosheets is 3% of the mass of the vinyl ester resin.

[0055] Example 4 Example 4 is basically the same as Example 1, except that: The mass of the modified boronene nanosheets is 0.3% of the mass of the vinyl ester resin.

[0056] Example 5 Example 5 is basically the same as Example 1, except that: The mass of the modified boronene nanosheets is 4% of the mass of the vinyl ester resin.

[0057] Example 6 Example 6 is basically the same as Example 1, except that: In step ①, the aluminum oxide powder used is nano aluminum oxide powder with an average particle size of 50nm.

[0058] Example 7 Example 7 is basically the same as Example 1, except that: In step ①, the aluminum oxide powder used is micron-sized aluminum oxide powder with an average particle size of 3μm.

[0059] Example 8 Example 8 is basically the same as Example 1, except that: Basalt fiber unidirectional fabric (area density of 280g / m²) was directly used. 2 The fiber-reinforced material with surface modification by silane coupling agent in Example 1 was replaced in the experiment.

[0060] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that: ① Formulation of ceramizable resin: Vinyl ester resin (SW-901, Shangwei) was heated to 45°C to reduce viscosity. Microsilica powder (average particle size 0.2 μm), mica powder (average particle size 15 μm), talc powder (average particle size 10 μm), borosilicate glass powder D245 (average particle size 10 μm), and alumina powder (a mixture of nano-alumina powder with an average particle size of 50 nm and micron-alumina powder with an average particle size of 3 μm in a mass ratio of 1.5:2) were added sequentially. The mixture was stirred at 100 rpm. The mixture was stirred at 0 rpm for 40 min; then magnesium hydroxide (average particle size 3 μm), expanded graphite (average particle size 150 μm), and nano-SiO2 sol (solid content 28 wt%, containing nano-SiO2 with a particle size distribution of 20-50 nm) were added and stirred at 700 rpm for 20 min; then an initiator (methyl ethyl ketone peroxide), an accelerator (cobalt isooctanoate), and a toughening agent (carboxyl-terminated liquid nitrile butadiene rubber CTBN) were added and stirred at 400 rpm. After stirring for 15 minutes at a constant temperature (m), vacuum degassing was performed at a vacuum degree of -0.08 MPa for 20 minutes to obtain a ceramicizable resin. The mass of the nano-SiO2 sol was 8% of the mass of the vinyl ester resin, the mass of the alumina powder was 10% of the mass of the vinyl ester resin, the total mass of the silica powder, mica powder, and talc powder was 6% of the mass of the vinyl ester resin, and the mass ratio of silica powder, mica powder, and talc powder was 4:3:2, the mass of the borosilicate glass powder was 5% of the mass of the vinyl ester resin, the total mass of the magnesium hydroxide and expanded graphite was 20% of the mass of the vinyl ester resin, and the mass ratio of magnesium hydroxide and expanded graphite was 4:1, the mass of methyl ethyl ketone peroxide was 1.8% of the mass of the vinyl ester resin, the mass of cobalt isooctanoate was 0.4% of the mass of the vinyl ester resin, and the mass of the carboxyl-terminated liquid nitrile rubber was 3% of the mass of the vinyl ester resin.

[0061] In this invention, the ceramicizable fiber prepregs for cladding building steel structures prepared in Examples 2-8 and Comparative Example 1 were applied to the surface of building steel structures under the same application and construction conditions as in Example 1, resulting in steel structure test specimens clad with different examples and comparative examples of prepregs. The clad steel structure test specimens were then subjected to an ablation test under a propane flame at 1100℃, as in Example 1, with the flame continuously ablation for 30 minutes. During the test, the structural retention at high temperatures, the temperature of the unexposed surface, and the state of the surface ceramic layer were observed and recorded. The cladding performance test results of the ceramicizable fiber prepregs for cladding building steel structures prepared in Examples 1-8 and Comparative Example 1 after ablation under a propane flame at 1100℃ for 30 minutes are shown in Table 2.

[0062] Table 2

[0063] As shown in Table 2, in the preferred embodiments 1-3 of this invention, the modified boronene nanosheets effectively promote the formation of a continuous and dense ceramic layer, significantly reduce the back-fired surface temperature, and exhibit excellent structural retention at high temperatures. However, in Embodiment 4, the amount of modified boronene nanosheets added was too low, resulting in limited ceramicization and insufficient density of the ceramic layer. In Embodiment 5, the amount of modified boronene nanosheets added was too high, leading to an increase in internal defects in the resin matrix. Although the ceramic layer was dense, its brittleness increased, thermal shock resistance decreased, and the back-fired surface temperature actually increased. In this invention, the oxide powder used as the high-temperature ceramic reinforcing powder, when... When nano-sized oxide powder and micron-sized oxide powder are used in combination, the high-temperature ceramicization performance of ceramicizable fiber prepreg for cladding of building steel structures is synergistically optimized. This may be because oxide powders of different particle sizes are conducive to forming a denser ceramic body during high-temperature sintering. However, in Example 6, only nano-sized oxide powder is used. Nano-sized powder has high activity and low sintering temperature, but its shrinkage rate is too large when used alone, which easily causes cracks. Although Example 7 has a stable skeleton structure, the micron-sized particles have large porosity, making it difficult to form a dense sintered body when used alone. Comparing the data from Examples 1 and 8, it is evident that the fiber-reinforced material of this invention, after surface modification with a silane coupling agent, significantly improves the interfacial bonding between the fiber and the resin matrix. The back-fired surface temperature of Example 1 is 70°C lower than that of the unmodified fiber-reinforced material system in Example 8, and the ceramic layer structure is more complete and exhibits no interfacial debonding at high temperatures. This indicates that surface modification with a silane coupling agent significantly enhances the fiber-resin interfacial bonding strength, not only providing reinforcement at room temperature but also ensuring stable support of the ceramic layer as a framework at high temperatures. In contrast, the ceramic layer formed in Comparative Example 1 without modified boronene nanosheets is porous and lacks structural integrity, exhibiting cracking and discontinuity.

[0064] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ceramicizable fiber prepreg for cladding steel structures, characterized in that, The ceramizable fiber prepreg for cladding steel structures comprises fiber reinforcing material and ceramizable resin impregnated in the fiber reinforcing material. The ceramizable resin comprises a resin matrix, a ceramizable composition, and a flame retardant; The ceramicizable composition comprises a ceramicizable precursor, oxide powder, ceramic filler, flux, and modified boronene nanosheets; The ceramicization precursor is one or more of polysiloxane, polysilsesquioxane, borosilicate sol, and nano-silica sol. The oxide powder is aluminum oxide powder and / or zirconium dioxide powder; The ceramic filler is one or more of the following: silica fume, kaolin, mica powder, and talc powder; The preparation of the modified boronene nanosheets includes the following steps: (1) Add silane coupling agent to ethanol aqueous solution and stir evenly to obtain ethanol aqueous solution of silane coupling agent. Then adjust the pH of ethanol aqueous solution of silane coupling agent to 4~5 and perform pre-hydrolysis for 20~60min to obtain ethanol aqueous solution of pre-hydrolyzed silane coupling agent. (2) Add boronene nanosheets to the ethanol aqueous solution of the pre-hydrolyzed silane coupling agent and perform ultrasonic treatment under inert gas protection to obtain a boronene nanosheet suspension. (3) The boronene nanosheet suspension was stirred at 50-60°C for 2-3 hours under inert gas protection, and then separated, washed and dried to obtain modified boronene nanosheets.

2. The ceramicizable fiber prepreg for cladding steel structures according to claim 1, characterized in that: In the ceramizable resin, the mass of the modified boronene nanosheets is 0.5 to 3% of the mass of the resin matrix.

3. The ceramicizable fiber prepreg for cladding steel structures according to claim 1, characterized in that: In step (1), the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and / or the ethanol aqueous solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8~10):

1.

4. The ceramicizable fiber prepreg for cladding steel structures according to claim 1, characterized in that: The raw materials for preparing the modified boronene nanosheets include boronene nanosheets, a silane coupling agent, and an aqueous ethanol solution in a mass ratio of 1:(0.5~1):(50~80); and / or The ultrasonic treatment temperature is 30~40℃, the ultrasonic treatment power is 300~500W, and the ultrasonic treatment time is 60~90min.

5. The ceramicizable fiber prepreg for cladding steel structures according to any one of claims 1 to 4, characterized in that: The fiber-reinforced material is basalt fiber-reinforced material; The resin matrix is ​​one or more of epoxy resin, phenolic resin, and vinyl ester resin; The flux is low-melting-point glass powder and / or zinc borate, wherein the low-melting-point glass powder is borosilicate glass powder and / or phosphate glass powder; The flame retardant is one or more of aluminum hydroxide, magnesium hydroxide, expanded graphite, and organophosphorus flame retardants; and / or The ceramicizable resin also contains an initiator, an accelerator, and a toughening agent. The initiator is methyl ethyl ketone peroxide, the accelerator is cobalt naphthenate and / or cobalt isooctanoate, and the toughening agent is carboxyl-terminated liquid nitrile rubber.

6. The ceramicizable fiber prepreg for cladding steel structures according to any one of claims 1 to 4, characterized in that: The ceramicizable resin contained in the prepreg for cladding steel structures is 20-60 wt% by mass; and / or In the ceramizable resin, the mass of the ceramization precursor is 5-20% of the mass of the resin matrix, the mass of the oxide powder is 5-20% of the mass of the resin matrix, the mass of the ceramic filler is 2-10% of the mass of the resin matrix, the flux is 3-15% of the mass of the resin matrix, and the flame retardant is 10-25% of the mass of the resin matrix.

7. The ceramicizable fiber prepreg for cladding steel structures according to any one of claims 1 to 4, characterized in that: The oxide powder comprises nano-oxide powder with a particle size of 20-200 nm and micro-oxide powder with a particle size of 1-5 μm in a mass ratio of (1.2-1.6):(1.8-2.5).

8. The ceramicizable fiber prepreg for cladding steel structures according to any one of claims 1 to 4, characterized in that: The fiber-reinforced material is a fiber-reinforced material that has been surface-modified with a silane coupling agent; The silane coupling agent is one or more of γ-glycidoxypropyltrimethoxysilane, N-(β-aminoethyl-γ-aminopropyl)trimethoxysilane, and γ-aminopropyltriethoxysilane.

9. The ceramicizable fiber prepreg for cladding steel structures according to claim 8, characterized in that: The preparation of fiber-reinforced materials with silane coupling agent surface modification includes: preparing a silane coupling agent solution with a concentration of 1-5 wt% using an aqueous ethanol solution, adjusting the pH of the silane coupling agent solution to 4-10 and pre-hydrolyzing it for 20-60 min to obtain a pre-hydrolyzed silane coupling agent solution, then immersing the fiber-reinforced material in the pre-hydrolyzed silane coupling agent solution, and then heat-treating it to obtain the fiber-reinforced material with silane coupling agent surface modification.

10. The ceramicizable fiber prepreg for cladding steel structures according to claim 9, characterized in that: The soaking treatment is a soaking treatment at room temperature for 5-30 minutes; and / or The heat treatment is performed at a temperature of 80~120℃ for 1~2 hours.

11. The method for preparing ceramizable fiber prepreg for cladding steel structures according to any one of claims 1 to 10, characterized in that, The preparation method includes the following steps: (a) The fiber-reinforced material is impregnated in a ceramicizable resin to obtain the impregnated fiber-reinforced material; (b) The impregnated fiber-reinforced material is rolled and pre-dried to obtain a ceramicizable fiber prepreg for cladding of building steel structures.

12. The preparation method according to claim 11, characterized in that: The immersion temperature is 40~55℃; The pressure of the roller pressing is 0.2~0.4MPa; The linear speed of the roller pressing is 0.3~0.6 m / min; and / or The pre-drying temperature is 80~90℃, and the pre-drying time is 3~5 minutes.

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