Lightweight high-strength waterproof gypsum board and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and particularly discloses a lightweight high-strength waterproof gypsum board and a preparation method thereof, the lightweight high-strength waterproof gypsum board comprises alpha-type high-strength gypsum, phosphogypsum, gradient lightweight aggregate, hydrophobic fiber, temperature-sensitive waterproof capsule and the like. The preparation method comprises the following steps: preparing the hydrophobic fiber, the gradient lightweight aggregate and the temperature-sensitive waterproof capsule, dry-mixing the components, mixing the dry-mixed components with water to form slurry, and pouring and curing. Lightweight and high strength are realized through cooperation of the gradient lightweight aggregate and the hydrophobic fiber, and the temperature-sensitive waterproof capsule releases components to fill pores during curing, so that the problem of insufficient early-stage waterproof performance is solved; the prepared gypsum board has the advantages of light weight, high strength, good waterproofness and durability.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a lightweight high-strength waterproof gypsum board and a preparation method thereof. Background Art

[0002] Waterproof gypsum board has a wide range of applications in the construction industry. It is often used in humid indoor environments, such as bathrooms, kitchens, and showers. These areas are subject to constant moisture and humidity, and while conventional gypsum board is susceptible to deformation and mold, waterproof gypsum board effectively resists these erosions, maintaining its stability and durability. Furthermore, waterproof gypsum board is widely used in basements, tunnels, and buildings in humid climates to meet the waterproofing and moisture-proofing requirements, ensuring the structural safety and functional performance of the building. Based on the above application scenarios, the existing technology proposes a high-strength, water-resistant paper-faced gypsum board. This solution isolates water vapor from contact by compounding a waterproofing agent in the core material of the paper-faced gypsum board and applying a layer of protective agent on the surface of the board. Among them, the composite waterproofing agent in the core material contains fly ash, ground slag, quicklime, silicone oil and silane coupling agent and other ingredients. These ingredients interact with each other to form a dense structure inside the board, improving the waterproof performance and mechanical properties. The protective agent coated on the side of the face paper in contact with the air is composed of fluoropolyether surfactants and silicone surfactants, which can form a protective layer on the surface of the board to further prevent water vapor from invading. This method of combining the addition of a protective film on the surface and the addition of a composite waterproofing agent inside comprehensively improves the waterproof performance of the board from both internal and external aspects, while also enhancing the mechanical properties of the gypsum board.

[0003] Although the above-mentioned gypsum board has improved its water resistance to a certain extent by adding raw materials such as modified starch to form a three-dimensional network structure to fill the gaps, it still has shortcomings in its waterproof performance. Specifically, the waterproofness of the core material is highly dependent on the hydration reaction of the inorganic components (fly ash, slag, quicklime) in the composite waterproofing agent to form a dense structure. This process takes time and before the board is completely hydrated and solidified (such as in the wet board stage or when encountering early water erosion), the waterproof effect is limited and the board is easily damaged by moisture. In addition, the above-mentioned waterproof gypsum board improves its waterproofness through adding materials and densification, but the pursuit of high waterproofness and high strength often requires increasing the material density, which is not conducive to the lightweight development of gypsum board. Summary of the Invention

[0004] In view of the technical defects existing in the background technology, the present invention proposes a lightweight, high-strength, waterproof gypsum board and a preparation method thereof, which solves the above technical problems and meets practical needs. The specific technical solution is as follows: A lightweight high-strength waterproof gypsum board comprises the following components, calculated by weight: 60-80 parts of α-type high-strength gypsum, 25-40 parts of phosphogypsum, 15-25 parts of gradient lightweight aggregate, 3.5-5 parts of reinforcing fiber, 5-10 parts of temperature-sensitive waterproof capsules, 1-2 parts of mineral activator, 0.1-0.5 parts of hydroxypropyl methylcellulose, and 15-25 parts of water; The reinforcing fiber is a mixture of polydopamine-modified glass fiber and carbon nanotube-grafted basalt fiber, the gradient lightweight aggregate is a mixture of modified hollow ceramic microbeads, graphene aerogel, and phosphogypsum whiskers, and the thermosensitive waterproof capsule includes, from the outside to the inside, a thermosensitive response outer shell layer, a dynamic buffer layer for maintaining the microenvironment, and a functional core composed of hydrophobically modified nano-silica and potassium methyl silicate.

[0005] As a further technical solution of the present invention, it is characterized in that the modified hollow ceramic microbeads: graphene aerogel: phosphogypsum whiskers (mass ratio) = 6:3:1, the modified hollow ceramic microbeads are prepared by modifying hollow ceramic microbeads by vapor deposition using a KH-550 silane coupling agent, and the graphene aerogel is prepared by vacuum impregnating graphene aerogel fragments with a nano-calcium stearate ethanol solution.

[0006] As a further technical solution of the present invention, the mineral activator is calcium aluminate, CaO / Al2O3 in the calcium aluminate is 1.5, and the viscosity of the hydroxypropyl methylcellulose is greater than 40000 mPa·s.

[0007] As a further technical solution of the present invention, the thermosensitive response shell layer is a polymer network formed by cross-linking poly(N-isopropylacrylamide) and a silane coupling agent, and its phase transition temperature is 32-35°C. The dynamic buffer layer is citrate filled between the thermosensitive shell layer and the functional core, which is used to maintain the pH of the microenvironment inside the thermosensitive shell layer at 8.0-9.0. The potassium methyl silicate in the functional core wraps the hydrophobically modified silica to form a core-shell structure.

[0008] A method for preparing a lightweight, high-strength, waterproof gypsum board comprises the following steps: S1. preparing reinforcing fibers; The glass fiber was immersed in a dopamine hydrochloride solution and then oscillated for 24 hours. The fiber was taken out, washed with deionized water, and dried to obtain polydopamine-modified glass fiber. Multi-walled carbon nanotubes were added to the mixed acid solution, refluxed at 70°C for 2 hours, centrifuged, washed with deionized water, and dried to obtain carboxylated carbon nanotubes. 0.5 g of carboxylated carbon nanotubes was dispersed in 200 mL of ultrapure water, and 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.6 g of N-hydroxysuccinimide were added in sequence. The mixture was activated by magnetic stirring for 30 minutes, and basalt fiber was added. After constant temperature oscillation reaction for 12 hours, the mixture was filtered, separated, washed with ethanol, and dried to obtain carbon nanotube-grafted basalt fiber. The polydopamine-modified glass fiber and the carbon nanotube-grafted basalt fiber were mixed in a mass ratio of 1:2 to obtain a reinforcing fiber. S2. Preparation of gradient lightweight aggregate; The hollow ceramic microbeads were placed in a fluidized bed reactor, and the KH-550 silane coupling agent was heated to 120°C for vaporization. Nitrogen was introduced to carry the vaporized KH-550 silane coupling agent, and the mixture was treated at 150°C for 30 minutes to obtain modified hollow ceramic microbeads. A 2wt% graphene oxide aqueous solution and 0.1M ascorbic acid were mixed in a volume ratio of 10:1, reacted in a 95°C water bath for 3 hours, immersed in liquid nitrogen for quenching, and immediately transferred to a grinder for crushing to obtain graphene aerogel fragments. The fragments were immersed in a 5wt% nano-calcium stearate ethanol solution, vacuum impregnated at -0.1MPa for 30 minutes, filtered and separated, and dried to obtain graphene aerogel. The modified hollow ceramic microbeads, graphene aerogel, and phosphogypsum whiskers were mixed in a mass ratio of 6:3:1 to obtain a gradient lightweight aggregate.

[0009] S3, preparing a temperature-sensitive waterproof capsule; Add hydrophobic SiO2, acrylamide, and deionized water into a three-necked flask, bubble nitrogen for 15 minutes to deoxygenate, heat to 60°C, add ammonium persulfate, and react under nitrogen protection with stirring for 1 hour, then cool, filter, and dry to obtain acrylamide-grafted SiO2. Mix the acrylamide-grafted SiO2, potassium methyl silicate, and deionized water, stir in a 90°C water bath for 40 minutes to obtain a reaction solution, and spray-dry the reaction solution to obtain a functional core powder. Sodium dodecylbenzenesulfonate and trisodium citrate were prepared into an aqueous phase, and the pH was adjusted to 8.5±0.1 with 1M NaOH. Dehydrated n-hexane and functional core powder were mixed and ultrasonically dispersed until there was no agglomeration. The oil phase was dropped into the aqueous phase while high-speed shear emulsification was started to obtain an emulsion intermediate. The emulsion intermediate was transferred to a reactor, and 100g of poly(N-isopropylacrylamide) and 1.2g of BIS cross-linking agent were added to the reactor in sequence. The mixture was dissolved by magnetic stirring and nitrogen was bubbled for 20 minutes for deoxygenation. Then, APS solution was added, stirring was maintained, and polymerization was carried out for 5 hours. During the reaction, 0.1M NaOH was added dropwise to adjust the pH of the reaction system to <8.3. After the reaction was completed, the mixture was centrifuged, washed with 50% ethanol and acetone in sequence, and dried to obtain a thermosensitive waterproof capsule. S4, preparing lightweight high-strength waterproof gypsum board; 80 parts of α-type high-strength gypsum, 25 parts of phosphogypsum, 15 parts of gradient lightweight aggregate, 5 parts of reinforcing fiber, 1 part of temperature-sensitive waterproof mineral activator, and 0.5 parts of hydroxypropyl methylcellulose are put into a blender for dry mixing, 10 parts of temperature-sensitive waterproof capsules and 20 parts of water are mixed, and the aqueous solution of temperature-sensitive waterproof capsules is sprayed into the dry material while stirring, and then high-speed shearing is carried out at 2000r / min for 30s to obtain gypsum slurry. The gypsum slurry is poured into a mold and cured to obtain a lightweight and high-strength waterproof gypsum board.

[0010] As a further technical solution of the present invention, in step S1, the basalt fiber is activated basalt fiber after mixed acid treatment. The preparation method of the activated basalt fiber is as follows: immersing basalt fiber with a diameter of 12-15 μm and a length of 3 mm in a mixed acid solution, ultrasonically treating it at 40°C for 1 hour, washing it with deionized water until it is neutral, and drying it at 80°C. The ratio of the mixed acid solution for treating the basalt fiber and the multi-walled carbon nanotubes is: concentrated H2SO4: concentrated HNO3 = 3:1 (v / v). As a further technical solution of the present invention, in step S3, the preparation method of the hydrophobic SiO2 is: 150g of nano-SiO2 and 500ml of 8% magnesium stearate-ethanol solution are added to a reactor, magnetically stirred and reacted at 75°C for 2h, and then filtered, washed, and dried at room temperature to obtain hydrophobic SiO2.

[0011] As a further technical solution of the present invention, in step S3, the mass ratio of the hydrophobic SiO2, acrylamide, and deionized water / ammonium persulfate is 150:20:100:1, the mass ratio of the acrylamide-grafted modified SiO2, potassium methyl silicate, and deionized water is 5:6:20, and the APS solution is used as follows: 1.8 g of APS is dissolved in 20 mL of deionized water and slowly injected into the reaction system at a rate of 1 mL / min using a syringe.

[0012] As a further technical solution of the present invention, step S3 also includes using KH-550 to perform surface passivation treatment on the prepared temperature-sensitive waterproof capsule. The specific method is: immersing the temperature-sensitive waterproof capsule with 1wt% KH-550 ethanol solution in an oscillating water bath at 20°C for 1 hour, and then filtering, washing, and freeze-drying to obtain a white fluffy powder.

[0013] As a further technical solution of the present invention, in step S4, the method for pouring the gypsum slurry into the mold for curing is: first curing it in a wet heat environment at 70°C and 90% RH for 6 hours to trigger the temperature-sensitive waterproof capsule to release the potassium methyl silicate inside it, and then vacuum drying it at 120°C and -0.08MPa to a moisture content of <5%.

[0014] The beneficial effects of the present invention are: The synergistic effect of gradient lightweight aggregate and reinforcing fiber reduces the density of gypsum board while utilizing the dense structure and fiber reinforcement effect formed by modified hollow ceramic microbeads, graphene aerogel, etc., so that the gypsum board is lightweight while maintaining its high strength. The temperature-sensitive waterproof capsule releases potassium methyl silicate and hydrophobic silica after hydration and curing, filling the pores and generating gel to block the channels, solving the problem of insufficient early waterproofing in the existing technology, and does not need to rely on long-term hydration of inorganic components. At the same time, mineral activators and hydroxypropyl methylcellulose optimize the reaction and construction performance, wet heat curing triggers the capsule action, and vacuum drying ensures the moisture content. The final gypsum board is lightweight, high-strength, well waterproof and durable. DETAILED DESCRIPTION

[0015] The following describes the implementation of the present invention in conjunction with relevant embodiments. The implementation of the present invention is not limited to the following embodiments, and the present invention relates to relevant necessary components in this technical field and should be regarded as a well-known technology in this technical field, which can be known and mastered by technical personnel in this technical field.

[0016] A lightweight high-strength waterproof gypsum board comprises the following components, calculated by weight: 60-80 parts of α-type high-strength gypsum, 25-40 parts of phosphogypsum, 15-25 parts of gradient lightweight aggregate, 3.5-5 parts of reinforcing fiber, 5-10 parts of temperature-sensitive waterproof capsules, 1-2 parts of mineral activator, 0.1-0.5 parts of hydroxypropyl methylcellulose, and 15-25 parts of water; The reinforcing fiber is a mixture of polydopamine-modified glass fiber and carbon nanotube-grafted basalt fiber, the gradient lightweight aggregate is a mixture of modified hollow ceramic microbeads, graphene aerogel, and phosphogypsum whiskers, and the thermosensitive waterproof capsule includes, from the outside to the inside, a thermosensitive response outer shell layer, a dynamic buffer layer for maintaining the microenvironment, and a functional core composed of hydrophobically modified nano-silica and potassium methyl silicate.

[0017] The present invention uses α-type high-strength gypsum and phosphogypsum as the main base materials, and the gradient lightweight aggregate is made by mixing modified hollow ceramic microspheres, graphene aerogel, and phosphogypsum whiskers in a specific proportion. The modified hollow ceramic microspheres are modified by vapor deposition of KH-550 silane coupling agent, thereby improving their hydrophobicity and bonding strength with other components. The graphene aerogel is further enhanced by vacuum impregnation with nano-calcium stearate ethanol solution to enhance its hydrophobicity. The graphene aerogel works together with the phosphogypsum whiskers to reduce the density of the board while utilizing its dense structure and fiber reinforcement effect to ensure that the board is lightweight while also having high strength.

[0018] The reinforcing fibers are a blend of polydopamine-modified glass fibers and carbon nanotube-grafted basalt fibers. The modified treatment enhances their hydrophilicity, further improving the mechanical properties of the board. The thermosensitive waterproof capsules consist of a thermoresponsive outer shell, a dynamic buffer layer, and a functional core. After hydration and curing, triggered by moist heat curing, the functional core releases potassium methyl silicate and hydrophobic silica, filling pores and forming a gel to block channels. This addresses the existing issue of core material waterproofing relying on the prolonged hydration of inorganic components, resulting in limited early waterproofing effectiveness. Without the need for prolonged hydration reactions of inorganic components, the board exhibits excellent waterproofing properties from an early stage. The mineral activator calcium aluminate promotes hydration, optimizing the board's strength and waterproofing properties. Hydroxypropyl methylcellulose improves water retention and adhesion during construction, facilitating the formation and curing of the gypsum slurry. The various components work together to reduce density, enhance strength, and improve waterproof performance. The final gypsum board is lightweight, high-strength, has good waterproofness and durability, effectively solving the problems of insufficient waterproof performance and unfavorable lightweight development in existing technologies.

[0019] As one of the preferred embodiments of the present invention, it is characterized in that the modified hollow ceramic microspheres: graphene aerogel: phosphogypsum whiskers (mass ratio) = 6:3:1, the modified hollow ceramic microspheres are prepared by modifying hollow ceramic microspheres by vapor deposition using a KH-550 silane coupling agent, and the graphene aerogel is prepared by vacuum impregnating graphene aerogel fragments with a nano-calcium stearate ethanol solution.

[0020] In the gradient lightweight aggregate, modified hollow ceramic microspheres, modified with KH-550, enhance hydrophobicity, while their hollow structure reduces board density. Graphene aerogel, treated with nano-calcium stearate, enhances water resistance, while its porous structure further reduces weight. It also forms a dense skeleton with the modified hollow ceramic microspheres. Phosphogypsum whiskers provide fiber reinforcement, increasing board strength. The three ingredients are combined in a balanced ratio to reduce board density while achieving a synergistic combination of lightweight and high strength through a dense structure and fiber reinforcement, enhancing overall water resistance.

[0021] As one of the preferred embodiments of the present invention, the mineral activator is calcium aluminate, CaO / Al2O3 in the calcium aluminate is 1.5, and the viscosity of the hydroxypropyl methylcellulose is greater than 40000 mPa·s.

[0022] Calcium aluminate, as a mineral activator, can effectively stimulate the activity of phosphogypsum, accelerate the hydration reaction, promote the generation of more dense hydration products, and improve the strength and waterproofness of the board. Hydroxypropyl methylcellulose has strong water retention and can delay water evaporation to ensure the full progress of the hydration reaction. At the same time, it improves the construction and workability of the gypsum slurry, making the slurry easier to shape during pouring, and can reduce porosity and enhance the density of the board structure. The two work together to optimize the reaction process and construction performance, helping the board to achieve light weight, high strength and good waterproofness.

[0023] As one of the preferred embodiments of the present invention, the thermosensitive response shell layer is a polymer network formed by cross-linking poly(N-isopropylacrylamide) and a silane coupling agent, and its phase transition temperature is 32-35°C. The dynamic buffer layer is citrate filled between the thermosensitive shell layer and the functional core, which is used to maintain the pH of the microenvironment inside the thermosensitive shell layer at 8.0-9.0. The potassium methyl silicate in the functional core wraps the hydrophobically modified silica to form a core-shell structure.

[0024] The thermosensitive responsive outer shell is triggered at a phase change temperature of 32-35°C, causing the thermosensitive waterproof capsule to release the functional core; the dynamic buffer layer maintains pH = 8.0-9.0 through citrate, which not only encapsulates potassium methyl silicate to prevent its premature hydrolysis and ineffectiveness, but also prevents the hydroxide generated by the hydrolysis of potassium methyl silicate from damaging the outer shell and causing the capsule to rupture, providing a stable release environment for the functional core; the potassium methyl silicate in the functional core encapsulates hydrophobically modified silica to form a core-shell structure, which fills the pores and generates gel to block the channels after release, solving the problem of insufficient early waterproofing in existing technologies, without relying on long-term hydration of inorganic components, thereby improving the waterproofness and durability of the board.

[0025] A method for preparing a lightweight, high-strength, waterproof gypsum board comprises the following steps: S1. preparing reinforcing fibers; The glass fiber was immersed in a dopamine hydrochloride solution and then oscillated for 24 hours. The fiber was taken out, washed with deionized water, and dried to obtain polydopamine-modified glass fiber. Multi-walled carbon nanotubes were added to the mixed acid solution, refluxed at 70°C for 2 hours, centrifuged, washed with deionized water, and dried to obtain carboxylated carbon nanotubes. 0.5 g of carboxylated carbon nanotubes was dispersed in 200 mL of ultrapure water, and 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.6 g of N-hydroxysuccinimide were added in sequence. The mixture was activated by magnetic stirring for 30 minutes, and basalt fiber was added. After constant temperature oscillation reaction for 12 hours, the mixture was filtered, separated, washed with ethanol, and dried to obtain carbon nanotube-grafted basalt fiber. The polydopamine-modified glass fiber and the carbon nanotube-grafted basalt fiber were mixed in a mass ratio of 1:2 to obtain a reinforcing fiber. S2. Preparation of gradient lightweight aggregate; The hollow ceramic microbeads were placed in a fluidized bed reactor, and the KH-550 silane coupling agent was heated to 120°C for vaporization. Nitrogen was introduced to carry the vaporized KH-550 silane coupling agent, and the mixture was treated at 150°C for 30 minutes to obtain modified hollow ceramic microbeads. A 2wt% graphene oxide aqueous solution and 0.1M ascorbic acid were mixed in a volume ratio of 10:1, reacted in a 95°C water bath for 3 hours, immersed in liquid nitrogen for quenching, and immediately transferred to a grinder for crushing to obtain graphene aerogel fragments. The fragments were immersed in a 5wt% nano-calcium stearate ethanol solution, vacuum impregnated at -0.1MPa for 30 minutes, filtered and separated, and dried to obtain graphene aerogel. The modified hollow ceramic microbeads, graphene aerogel, and phosphogypsum whiskers were mixed in a mass ratio of 6:3:1 to obtain a gradient lightweight aggregate.

[0026] S3, preparing a temperature-sensitive waterproof capsule; Add hydrophobic SiO2, acrylamide, and deionized water into a three-necked flask, bubble nitrogen for 15 minutes to deoxygenate, heat to 60°C, add ammonium persulfate, and react under nitrogen protection with stirring for 1 hour, then cool, filter, and dry to obtain acrylamide-grafted SiO2. Mix the acrylamide-grafted SiO2, potassium methyl silicate, and deionized water, stir in a 90°C water bath for 40 minutes to obtain a reaction solution, and spray-dry the reaction solution to obtain a functional core powder. Sodium dodecylbenzenesulfonate and trisodium citrate were prepared into an aqueous phase, and the pH was adjusted to 8.5±0.1 with 1M NaOH. Dehydrated n-hexane and functional core powder were mixed and ultrasonically dispersed until there was no agglomeration. The oil phase was dropped into the aqueous phase while high-speed shear emulsification was started to obtain an emulsion intermediate. The emulsion intermediate was transferred to a reactor, and 100g of poly(N-isopropylacrylamide) and 1.2g of BIS cross-linking agent were added to the reactor in sequence. The mixture was dissolved by magnetic stirring and nitrogen was bubbled for 20 minutes for deoxygenation. Then, APS solution was added, stirring was maintained, and polymerization was carried out for 5 hours. During the reaction, 0.1M NaOH was added dropwise to adjust the pH of the reaction system to <8.3. After the reaction was completed, the mixture was centrifuged, washed with 50% ethanol and acetone in sequence, and dried to obtain a thermosensitive waterproof capsule. S4, preparing lightweight high-strength waterproof gypsum board; 80 parts of α-type high-strength gypsum, 25 parts of phosphogypsum, 15 parts of gradient lightweight aggregate, 5 parts of reinforcing fiber, 1 part of temperature-sensitive waterproof mineral activator, and 0.5 parts of hydroxypropyl methylcellulose are put into a blender for dry mixing, 10 parts of temperature-sensitive waterproof capsules and 20 parts of water are mixed, and the aqueous solution of temperature-sensitive waterproof capsules is sprayed into the dry material while stirring, and then high-speed shearing is carried out at 2000r / min for 30s to obtain gypsum slurry. The gypsum slurry is poured into a mold and cured to obtain a lightweight and high-strength waterproof gypsum board.

[0027] The preparation method of the present invention achieves performance optimization and synergistic effects of each component through a multi-step process. When preparing reinforcing fibers, the mixing process of polydopamine-modified glass fibers and carbon nanotube-grafted basalt fibers gives the reinforcing fiber system compatibility and reinforcement effects, thereby improving the mechanical properties of the board without increasing the density. In the preparation of gradient lightweight aggregates, the vapor deposition modification of modified hollow ceramic microspheres and the vacuum impregnation treatment of graphene aerogel enhance their hydrophobicity and structural stability. After compounding with phosphogypsum whiskers, a dense reinforced skeleton is formed while reducing the density. The preparation process of the thermosensitive waterproof capsule ensures that it is triggered to release during wet heat curing at 32-35°C. The dynamic buffer layer maintains pH stability to avoid the failure of potassium methyl silicate and damage to the outer shell layer. After the functional core is released, the pores are filled and the channels are blocked, solving the problem of early waterproofing. High-speed shearing during the preparation of gypsum slurry ensures uniform dispersion of the components, wet heat curing at 70°C triggers the capsule action, and vacuum drying at 120°C reduces the moisture content. The final board is lightweight, high-strength, and has good waterproofness and durability.

[0028] As one of the preferred embodiments of the present invention, in step S1, the basalt fiber is activated basalt fiber after mixed acid treatment. The preparation method of the activated basalt fiber is: immersing basalt fiber with a diameter of 12-15 μm and a length of 3 mm in a mixed acid solution, ultrasonically treating it at 40°C for 1 hour, washing it with deionized water until it is neutral, and drying it at 80°C. The ratio of the mixed acid solution for treating the basalt fiber and multi-walled carbon nanotubes is: concentrated H2SO4: concentrated HNO3 = 3:1 (v / v).

[0029] By ultrasonically treating basalt fibers with mixed acid at 40°C, their surface is activated, introducing functional groups such as carboxyl groups and increasing their reactivity. This facilitates the subsequent grafting of carbon nanotubes onto the basalt fibers via activation with 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, forming a stable covalent bond and increasing the integrity and strength of the reinforced fibers. The activation treatment also improves the grafting ability of basalt fibers and carbon nanotubes, synergizing with polydopamine-modified glass fibers to enhance the mechanical properties of the sheet without increasing density, helping to achieve lightweight and high strength.

[0030] The reinforcing fiber prepared by the present invention is made of polydopamine-modified glass fiber and carbon nanotube-grafted basalt fiber mixed in a specific ratio. The polydopamine coating improves the hydrophilicity and interfacial bonding of the glass fiber, making it form a stronger bond with the gypsum matrix. The carbon nanotube-grafted basalt fiber is activated by mixed acid surface and then grafted with a three-dimensional network structure of carbon nanotubes, which not only strengthens the basalt fiber itself, but also forms a microscopic reinforcing skeleton with it, greatly improving the overall stiffness and toughness of the fiber system. The synergistic effect of polydopamine-modified glass fiber and carbon nanotube-grafted basalt fiber constructs a multi-scale reinforcing network in the gypsum matrix, which not only disperses the external load but also hinders the generation of microcracks, effectively improving the flexural strength, impact resistance and fracture toughness of the board. At the same time, the modification gives the fiber good hydrophilicity, which can additionally increase the density of the system. The reinforcing fiber can also cooperate with the phosphogypsum whiskers in the gradient lightweight aggregate to form a multi-level fiber reinforcement effect, jointly supporting the lightweight skeleton and strengthening the structural integrity, which is the basis for the gypsum board to achieve both lightness and high strength.

[0031] As one of the preferred embodiments of the present invention, in step S3, the preparation method of the hydrophobic SiO2 is: 150g of nano-SiO2 and 500ml of 8% magnesium stearate-ethanol solution are added to a reactor, magnetically stirred and reacted at 75°C for 2h, and then filtered, washed, and dried at room temperature to obtain hydrophobic SiO2.

[0032] Nano-SiO2 was reacted with an 8% magnesium stearate-ethanol solution at 75°C under magnetic stirring for 2 hours. The hydrophobic long chains of magnesium stearate can be coated on the SiO2 surface through chemical bonding or physical adsorption, forming a hydrophobic layer, significantly enhancing the hydrophobicity of the SiO2. As a component of the functional core, the hydrophobic SiO2 forms a core-shell structure with potassium methyl silicate. After the thermosensitive capsule is released, it can effectively fill the pores of the board and, together with the gel formed by potassium methyl silicate, block water channels, enhancing the waterproof performance.

[0033] As one of the preferred embodiments of the present invention, in step S3, the mass ratio of the hydrophobic SiO2, acrylamide, and deionized water / ammonium persulfate is 150:20:100:1, the mass ratio of the acrylamide-grafted modified SiO2, potassium methyl silicate, and deionized water is 5:6:20, and the APS solution is used as follows: 1.8 g of APS is dissolved in 20 mL of deionized water and slowly injected into the reaction system at a rate of 1 mL / min using a syringe.

[0034] As one of the preferred embodiments of the present invention, step S3 also includes using KH-550 to perform surface passivation treatment on the prepared temperature-sensitive waterproof capsule. The specific method is: immersing the temperature-sensitive waterproof capsule with 1wt% KH-550 ethanol solution in an oscillating water bath at 20°C for 1 hour, and then filtering, washing, and freeze-drying to obtain a white fluffy powder.

[0035] In the reaction system of hydrophobic SiO2, acrylamide, water, and ammonium persulfate, ammonium persulfate acts as an initiator to effectively initiate the grafting of acrylamide onto hydrophobic SiO2, forming uniform acrylamide-grafted modified SiO2 and enhancing the binding force with potassium methyl silicate. In the reaction system of grafted modified SiO2, potassium methyl silicate, and water, potassium methyl silicate fully wraps the grafted SiO2 to form a stable core-shell structure, which synergistically fills pores and blocks channels after release. The slow injection of APS solution can control the polymerization reaction rate, ensure uniform cross-linking of the thermosensitive outer shell layer, and accurately achieve phase transition temperature, so that the capsule can accurately release the functional core during wet heat curing, thereby improving waterproof reliability.

[0036] As one of the preferred embodiments of the present invention, in step S4, the method for pouring the gypsum slurry into the mold for curing is: first, curing it in a wet heat at 70°C and 90% RH for 6 hours to trigger the temperature-sensitive waterproof capsule to release the potassium methyl silicate inside it, and then vacuum drying it at 120°C and -0.08MPa to a moisture content of <5%.

[0037] Curing at 70°C and 90% RH for 6 hours, the temperature reaches the phase transition temperature of the thermosensitive outer shell at 32-35°C, triggering the thermosensitive waterproof capsule to release potassium methyl silicate and hydrophobic silica, filling the pores and forming a gel to block the channels, thus resolving the problem of insufficient waterproofing in the early stage. Subsequently, vacuum drying is performed at 120°C and -0.08MPa to a moisture content of less than 5%. The high temperature and vacuum environment accelerates water evaporation, reduces the moisture content of the board, improves the structural stability of the board, and further promotes the reaction and bonding between the components, enhancing the board's strength and durability, and ensuring long-term waterproofing.

[0038] Example 1

[0039] A method for preparing a lightweight, high-strength, waterproof gypsum board comprises the following steps: S1. preparing reinforcing fibers; The alkali-free glass fiber (diameter 9-12 μm, length 6 mm) was immersed in acetone solution and ultrasonically cleaned for 30 minutes (power 300 W, frequency 40 kHz) to remove the surface wetting agent. The fiber was rinsed with deionized water until neutral and dried in a 105°C oven for 2 hours. 2 g of dopamine hydrochloride was dissolved in 1 L of Tris-HCl buffer (10 mM, pH = 8.5) and magnetically stirred until completely dissolved. The pretreated glass fiber was immersed in the solution, and the mass ratio of fiber to solution was controlled to be 1:100. The reaction was continued at 120 rpm in a constant temperature oscillator for 24 hours (temperature 25 ± 1°C). The fiber was removed and rinsed with deionized water until the rinse solution was colorless. The fiber was then vacuum dried at 60°C for 6 hours to obtain polydopamine-modified glass fiber.

[0040] Basalt fibers (diameter 12-15 μm, length 3 mm) were immersed in a mixed acid solution (concentrated H2SO4:concentrated HNO3 = 3:1), ultrasonically treated at 40 °C for 1 h (power 350 W), filtered and separated, washed with deionized water until neutral, and dried at 80 °C for use; multi-walled carbon nanotubes (MWCNTs, outer diameter 20-30 nm) were added to a mixed acid solution (concentrated H2SO4:concentrated HNO3 = 3:1), refluxed at 70 °C for 2 h, centrifuged, washed with deionized water until pH = 7, and dried at 60 °C to obtain carboxylated carbon nanotubes. 0.5 g of carboxylated carbon nanotubes were dispersed in 200 mL of ultrapure water, 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) was added, and 0.6 g of N-hydroxysuccinimide (NHS) was activated by magnetic stirring for 30 minutes (25°C), and the activated basalt fiber was added at a fiber to solution mass ratio of 1:50. The reaction was carried out in a constant temperature oscillator at 100 rpm for 12 hours. The fiber was taken out, rinsed with ethanol three times, and vacuum dried at 70°C for 4 hours to obtain carbon nanotube-grafted basalt fiber. The polydopamine-modified glass fiber and the carbon nanotube-grafted basalt fiber were mixed in a mass ratio of 1:2 to obtain reinforced fiber.

[0041] S2. Preparation of gradient lightweight aggregate; Hollow ceramic microbeads with a particle size of 50-80 μm were placed in a fluidized bed reactor. γ-Aminopropyltriethoxysilane (KH-550) was heated to 120°C to vaporize it. Nitrogen was then introduced (at a flow rate of 5 L / min) to carry the vaporized silane. The microbeads were treated at 150°C for 30 minutes to form a covalently bonded layer on the surface. Residues were removed by nitrogen purge for 10 minutes to obtain modified hollow ceramic microbeads. A 2 wt% aqueous solution of graphene oxide (20-50 μm in diameter) was mixed with 0.1 M ascorbic acid in a 10:1 volume ratio and reacted in a 95°C waterbath for 3 hours to form a three-dimensional network gel. The gel was then quenched by immersion in liquid nitrogen and immediately transferred to a grinder at 8000 rpm for 30 seconds. Fragments of 100-300 μm were collected by sieving, immersed in a 5 wt% solution of nano-calcium stearate in ethanol, and vacuum-treated at -0.1 MPa for 30 minutes. The resulting graphene aerogel was then dried at 60°C. Modified hollow ceramic microspheres, graphene aerogel and phosphogypsum whiskers were mixed in a mass ratio of 6:3:1 to obtain gradient lightweight aggregate.

[0042] S3, preparing a temperature-sensitive waterproof capsule; Weigh 150g of pretreated nano-SiO2 and add it to a 1L reactor, add 30g of magnesium stearate and 500mL of anhydrous ethanol, turn on ultrasonic treatment (40kHz, 500W) for 30min, heat the oil bath to 75℃, magnetically stir (600rpm) for 2h, vacuum filter, wash three times with 200mL of acetone, and dry in an 80℃ oven for 6h to obtain hydrophobic SiO2.

[0043] Take 50g of hydrophobic SiO2 and add it to a 500mL three-necked flask, add 20g of acrylamide and 100mL of deionized water, bubble nitrogen for 15min to deoxygenate, heat to 60℃, add 1g of ammonium persulfate (APS), stir under nitrogen protection (300rpm) for 1h, immediately cool in an ice bath, filter, and vacuum dry at 50℃ to obtain acrylamide-grafted modified SiO2.

[0044] 50g of SiO2 grafted with acrylamide was added with 60g of potassium methyl silicate and 200mL of deionized water, stirred in a 90℃ water bath (400rpm) for 40min, and then spray-dried (inlet air temperature: 180℃, outlet air temperature: 80℃, atomization pressure: 0.3MPa) to obtain a functional core powder. Measure 1200mL of deionized water and add it to a 2L beaker. Add 8g of sodium dodecylbenzenesulfonate (SDS) and 5g of trisodium citrate. Stir magnetically (500rpm) until completely dissolved. Adjust the pH to 8.5±0.1 with 1M NaOH to obtain an aqueous phase. Weigh 450g of the functional core and add it to a 1L beaker. Add 450mL of dehydrated n-hexane and ultrasonically disperse (40kHz, 30min) until there is no agglomeration to obtain an oil phase. Transfer the oil phase to a separatory funnel and control the drop rate to 5mL / min while dripping it into the aqueous phase while turning on high-speed shear (10000rpm, 8min) to obtain an emulsion intermediate.

[0045] The emulsion was transferred to a 2L reactor and 100g NIPAM and 1.2g BIS cross-linker were added. The mixture was dissolved by magnetic stirring (300rpm), and nitrogen was bubbled for 20min to deoxygenate. The oil bath was heated to 38±0.5℃, 1.8g APS was dissolved in 20mL deionized water and slowly injected into the reaction system with a syringe (1mL / min). The stirring was maintained at 300rpm and the polymerization was carried out for 5h. The pH of the reaction was monitored every 30min. The pH was sampled and tested. If the pH was <8.3, 0.1M NaOH was added dropwise to adjust it. After the reaction was completed, the mixture was centrifuged and washed with 50% ethanol and acetone in sequence, and dried to obtain thermosensitive waterproof capsules. The thermosensitive waterproof capsules were then immersed in 1wt% KH-550 ethanol solution in a shaking water bath at 20℃ for 1h, and then filtered, washed, and freeze-dried to obtain a white fluffy powder.

[0046] S4, preparing lightweight high-strength waterproof gypsum board; 80 parts of α-type high-strength gypsum, 25 parts of phosphogypsum, 15 parts of gradient lightweight aggregate, 5 parts of reinforcing fiber, 1 part of temperature-sensitive waterproof mineral activator, and 0.5 parts of hydroxypropyl methylcellulose are put into a blender for dry mixing, 10 parts of temperature-sensitive waterproof capsules and 20 parts of water are mixed, and the aqueous solution of temperature-sensitive waterproof capsules is sprayed into the dry material while stirring, and then high-speed shearing is carried out at 2000r / min for 30s to obtain gypsum slurry. The gypsum slurry is poured into a mold and cured to obtain a lightweight and high-strength waterproof gypsum board.

[0047] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the temperature-sensitive waterproof capsule component is eliminated, and 10 parts of the temperature-sensitive waterproof capsule in the formula are replaced by an equal amount of α-type high-strength gypsum (i.e., the α-type high-strength gypsum is increased to 90 parts), and the other components and preparation process remain unchanged.

[0048] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the gradient lightweight aggregate is replaced with a single aggregate, and the gradient lightweight aggregate (modified hollow ceramic microspheres: graphene aerogel: phosphogypsum whiskers = 6:3:1) is replaced with an equal mass of unmodified hollow ceramic microspheres (particle size 50-80 μm), and the other components and preparation process remain unchanged.

[0049] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that unmodified fiber is used, and the reinforcing fiber (polydopamine-modified glass fiber + carbon nanotube-grafted basalt fiber) is replaced by an equal mass of ordinary mixed fiber (unmodified glass fiber and unmodified basalt fiber are mixed in the original ratio of 1:2), and the other components and preparation process remain unchanged.

[0050] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the curing process is changed, the 70°C / 90% RH wet heat curing and 120°C vacuum drying steps are eliminated, and standard curing conditions are adopted (curing at 40°C and 60% RH for 24 hours followed by natural drying to a moisture content of <5%). The other components and preparation process remain unchanged.

[0051] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the mineral activator is replaced, the calcium aluminate (CaO / Al2O3=1.5) is replaced by ordinary Portland cement in equal parts by mass, and the other components and preparation process remain unchanged.

[0052] Performance evaluation 1. Compressive strength MPa, softening coefficient, and surface density kg / m 2 , bending failure load, and impact resistance test.

[0053] 2. Water absorption test method: Place the gypsum boards of Example 1 and Comparative Examples 1-5 in an oven and dry them at a constant temperature for 72 hours, then take them out and weigh G1. Then soak them in water for 1 day and 3 days respectively, then take them out and weigh G2. Calculate the water absorption of the gypsum boards using the following formula: W = (G2-G1) / G1×100%

[0054] By comparing Example 1 with Comparative Example 1, it can be seen that after the temperature-sensitive waterproof capsules in Comparative Example 1 were removed and replaced with an equal amount of α-type high-strength gypsum, the compressive strength decreased from 7.6MPa to 6.8MPa, the softening coefficient decreased from 0.95 to 0.82, the bending failure load / deadweight multiple decreased from 3.5 to 2.8, the impact resistance decreased from 10 times to 7 times, the surface density increased from 6.50kg / m² to 70.0kg / m², the 1d water absorption rate increased from 1.45% to 5.2%, and the 3d water absorption rate increased from 4.4% to 12.1%. This shows that the presence of the temperature-sensitive waterproof capsules can significantly improve the compressive strength, softening coefficient, bending and impact resistance of the board, while reducing the surface density and water absorption rate. By releasing the functional core to fill the pores and block the channels, it solves the problem of insufficient waterproofing in the early stage, and does not rely on the long-term hydration of inorganic components, which plays an important role in improving the lightweight, high strength and waterproof performance of the board.

[0055] Comparing Example 1 with Comparative Example 2, after replacing the gradient lightweight aggregate with unmodified hollow ceramic microspheres of equal mass in Comparative Example 2, the compressive strength dropped to 5.2MPa, the flexural failure load / deadweight ratio dropped to 2.0, the impact resistance dropped to 6 times, the surface density increased to 6.80kg / m², the 1d water absorption rate increased to 2.8%, and the 3d water absorption rate increased to 8.3%. This shows that it is crucial to compound the modified hollow ceramic microspheres, graphene aerogel, and phosphogypsum whiskers in the gradient lightweight aggregate in a specific proportion. The modification process enhances the hydrophobicity and bonding strength of each component. The three synergistically form a dense skeleton and exert a fiber reinforcement effect, significantly improving the strength and waterproof performance of the board while reducing the density. A single unmodified aggregate cannot achieve this synergistic optimization effect.

[0056] A comparison of Example 1 and Comparative Example 3 shows that after using unmodified fibers in Comparative Example 3, the compressive strength dropped to 6.0 MPa, the softening coefficient dropped to 0.80, the flexural failure load / deadweight ratio dropped to 2.3, the impact resistance dropped to 5 times, the 1-day water absorption rate increased to 3.0%, and the 3-day water absorption rate increased to 7.0%. This shows that the modification of the reinforcing fibers is indispensable. The modification of polydopamine-modified glass fibers and carbon nanotube-grafted basalt fibers improves the hydrophilicity and interfacial bonding of the fibers, constructs a multi-scale reinforcement network within the gypsum matrix, effectively disperses the load, and hinders the generation of microcracks, thereby significantly improving the mechanical properties and waterproof properties of the board. The reinforcement effect of the unmodified fibers is obviously insufficient.

[0057] A comparison of Example 1 and Comparative Example 4 shows that after changing the curing process in Comparative Example 4, the softening coefficient dropped to 0.79, the flexural failure load / deadweight ratio dropped to 3.0, the impact resistance dropped to 8 times, the 1-day water absorption rate increased to 4.8%, and the 3-day water absorption rate increased to 11.5%. This demonstrates that specific curing processes significantly impact the performance of the board. Curing at 70°C and 90% RH triggers the release of the functional core of the temperature-sensitive waterproof capsules, promptly filling pores and blocking channels. Vacuum drying at 120°C reduces moisture content and promotes component reactions. These two combined effects ensure the waterproofness, strength, and durability of the board. Standard curing conditions fail to fully utilize the temperature-sensitive waterproof capsules, resulting in a decline in waterproofness and mechanical properties.

[0058] Comparing Example 1 with Comparative Example 5, after replacing the mineral activator with ordinary Portland cement in Comparative Example 5, the compressive strength dropped to 6.3 MPa, the softening coefficient dropped to 0.85, the flexural failure load / deadweight ratio dropped to 2.7, the impact resistance dropped to 7 times, the 1-day water absorption rate increased to 2.9%, and the 3-day water absorption rate increased to 7.2%. This shows that calcium aluminate has unique advantages as a mineral activator. It can more effectively stimulate the activity of phosphogypsum, accelerate the hydration reaction, and promote the production of more dense hydration products, thereby better improving the strength and waterproofing of the board. Ordinary Portland cement is not as effective as calcium aluminate in stimulating and optimizing performance.

[0059] The above description is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A lightweight, high-strength, waterproof gypsum board, characterized in that: The composition includes the following components in parts by weight: 60-80 parts of α-type high-strength gypsum, 25-40 parts of phosphogypsum, 15-25 parts of gradient lightweight aggregate, 3.5-5 parts of reinforcing fiber, 5-10 parts of temperature-sensitive waterproof capsule, 1-2 parts of mineral activator, 0.1-0.5 parts of hydroxypropyl methylcellulose, and 15-25 parts of water; The reinforcing fiber is a mixture of polydopamine-modified glass fiber and carbon nanotube-grafted basalt fiber, the gradient lightweight aggregate is a mixture of modified hollow ceramic microbeads, graphene aerogel, and phosphogypsum whiskers, and the thermosensitive waterproof capsule includes, from the outside to the inside, a thermosensitive response outer shell layer, a dynamic buffer layer for maintaining the microenvironment, and a functional core composed of hydrophobically modified nano-silica and potassium methyl silicate.

2. A lightweight, high-strength, waterproof gypsum board according to claim 1, characterized in that: The modified hollow ceramic microbeads: graphene aerogel: phosphogypsum whiskers (mass ratio) = 6:3:

1. The modified hollow ceramic microbeads are prepared by modifying hollow ceramic microbeads through vapor deposition with a KH-550 silane coupling agent. The graphene aerogel is prepared by vacuum impregnating graphene aerogel fragments with a nano-calcium stearate ethanol solution.

3. A lightweight, high-strength, waterproof gypsum board according to claim 1, characterized in that: The mineral activator is calcium aluminate, wherein CaO / Al2O3 in the calcium aluminate is 1.5, and the viscosity of the hydroxypropyl methylcellulose is greater than 40000 mPa·s.

4. The lightweight, high-strength, waterproof gypsum board according to claim 1, characterized in that: The thermosensitive response shell layer is a polymer network formed by cross-linking poly(N-isopropylacrylamide) and a silane coupling agent, and its phase transition temperature is 32-35°C. The dynamic buffer layer is citrate filled between the thermosensitive shell layer and the functional core, which is used to maintain the pH of the microenvironment inside the thermosensitive shell layer at 8.0-9.

0. The potassium methyl silicate in the functional core wraps the hydrophobically modified silica to form a core-shell structure.

5. A method for preparing a lightweight, high-strength, waterproof gypsum board according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. preparing reinforcing fibers; The glass fiber was immersed in a dopamine hydrochloride solution and then oscillated for 24 hours. The fiber was taken out, washed with deionized water, and dried to obtain polydopamine-modified glass fiber. Multi-walled carbon nanotubes were added to the mixed acid solution, refluxed at 70°C for 2 hours, centrifuged, washed with deionized water, and dried to obtain carboxylated carbon nanotubes. 0.5 g of carboxylated carbon nanotubes was dispersed in 200 mL of ultrapure water, and 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.6 g of N-hydroxysuccinimide were added in sequence. The mixture was activated by magnetic stirring for 30 minutes, and basalt fiber was added. After constant temperature oscillation reaction for 12 hours, the mixture was filtered, separated, washed with ethanol, and dried to obtain carbon nanotube-grafted basalt fiber. The polydopamine-modified glass fiber and the carbon nanotube-grafted basalt fiber were mixed in a mass ratio of 1:2 to obtain a reinforcing fiber. S2. Preparation of gradient lightweight aggregate; The hollow ceramic microspheres were placed in a fluidized bed reactor, and the KH-550 silane coupling agent was heated to 120°C for vaporization. Nitrogen was introduced to carry the vaporized KH-550 silane coupling agent, and the mixture was treated at 150°C for 30 minutes to obtain modified hollow ceramic microspheres. A 2wt% graphene oxide aqueous solution and 0.1M ascorbic acid were mixed in a volume ratio of 10:1, reacted in a 95°C water bath for 3 hours, immersed in liquid nitrogen for quenching, and immediately transferred to a grinder for crushing to obtain graphene aerogel fragments. The fragments were immersed in a 5wt% nano-calcium stearate ethanol solution, vacuum impregnated at -0.1MPa for 30 minutes, filtered and separated, and dried to obtain graphene aerogel. The modified hollow ceramic microspheres, graphene aerogel, and phosphogypsum whiskers were mixed in a mass ratio of 6:3:1 to obtain a gradient lightweight aggregate. S3, preparing a temperature-sensitive waterproof capsule; Add hydrophobic SiO2, acrylamide, and deionized water into a three-necked flask, bubble nitrogen for 15 minutes to deoxygenate, heat to 60°C, add ammonium persulfate, and react under nitrogen protection with stirring for 1 hour, then cool, filter, and dry to obtain acrylamide-grafted SiO2. Mix the acrylamide-grafted SiO2, potassium methyl silicate, and deionized water, stir in a 90°C water bath for 40 minutes to obtain a reaction solution, and spray-dry the reaction solution to obtain a functional core powder. Sodium dodecylbenzenesulfonate and trisodium citrate were prepared into an aqueous phase, and the pH was adjusted to 8.5±0.1 with 1M NaOH. Dehydrated n-hexane and functional core powder were mixed and ultrasonically dispersed until there was no agglomeration. The oil phase was dropped into the aqueous phase while high-speed shear emulsification was started to obtain an emulsion intermediate. The emulsion intermediate was transferred to a reactor, and 100g of poly(N-isopropylacrylamide) and 1.2g of BIS cross-linking agent were added to the reactor in sequence. The mixture was dissolved by magnetic stirring and nitrogen was bubbled for 20 minutes for deoxygenation. Then, APS solution was added, stirring was maintained, and polymerization was carried out for 5 hours. During the reaction, 0.1M NaOH was added dropwise to adjust the pH of the reaction system to <8.

3. After the reaction was completed, the mixture was centrifuged, washed with 50% ethanol and acetone in sequence, and dried to obtain a thermosensitive waterproof capsule. S4, preparing lightweight high-strength waterproof gypsum board; 80 parts of α-type high-strength gypsum, 25 parts of phosphogypsum, 15 parts of gradient lightweight aggregate, 5 parts of reinforcing fiber, 1 part of temperature-sensitive waterproof mineral activator, and 0.5 parts of hydroxypropyl methylcellulose are put into a blender for dry mixing, 10 parts of temperature-sensitive waterproof capsules and 20 parts of water are mixed, and the aqueous solution of temperature-sensitive waterproof capsules is sprayed into the dry material while stirring, and then high-speed shearing is carried out at 2000r / min for 30s to obtain gypsum slurry. The gypsum slurry is poured into a mold and cured to obtain a lightweight and high-strength waterproof gypsum board.

6. The method for preparing a lightweight, high-strength, waterproof gypsum board according to claim 5, characterized in that: In step S1, the basalt fiber is activated basalt fiber after mixed acid treatment. The preparation method of the activated basalt fiber is: immersing basalt fiber with a diameter of 12-15 μm and a length of 3 mm in a mixed acid solution, ultrasonically treating it at 40°C for 1 hour, washing it with deionized water until it is neutral, and drying it at 80°C. The ratio of the mixed acid solution for treating the basalt fiber and multi-walled carbon nanotubes is: concentrated H2SO4: concentrated HNO3 = 3:1 (v / v).

7. The method for preparing a lightweight, high-strength, waterproof gypsum board according to claim 5, characterized in that: In step S3, the preparation method of the hydrophobic SiO2 is as follows: 150g of nano-SiO2 and 500ml of 8% magnesium stearate-ethanol solution are added to a reactor, magnetically stirred at 75°C for 2h, and then filtered, washed, and dried at room temperature to obtain hydrophobic SiO2.

8. The method for preparing a lightweight, high-strength, waterproof gypsum board according to claim 5, characterized in that: In step S3, the mass ratio of the hydrophobic SiO2, acrylamide, and deionized water ammonium persulfate is 150:20:100:1, the mass ratio of the acrylamide grafted modified SiO2, potassium methyl silicate, and deionized water is 5:6:20, and the method for using the APS solution is as follows: 1.8 g APS is dissolved in 20 mL of deionized water and slowly injected into the reaction system at a rate of 1 mL / min using a syringe.

9. The method for preparing a lightweight, high-strength, waterproof gypsum board according to claim 5, characterized in that: Step S3 also includes using KH-550 to perform surface passivation treatment on the prepared thermosensitive waterproof capsule. The specific method is: immersing the thermosensitive waterproof capsule with 1wt% KH-550 ethanol solution in an oscillating water bath at 20°C for 1 hour, then filtering, washing, and freeze-drying to obtain a white fluffy powder.

10. The method for preparing a lightweight, high-strength, waterproof gypsum board according to claim 5, characterized in that: In step S4, the gypsum slurry is poured into the mold for curing by: first curing at 70°C and 90% RH for 6 hours to trigger the temperature-sensitive waterproof capsule to release the potassium methyl silicate inside it, and then vacuum drying at 120°C and -0.08MPa to a moisture content of <5%.

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