High performance gypsum-based composite and method of making same

Abstract

The application discloses a kind of high-performance gypsum-based composite material and preparation method thereof, belong to building material technical field, kaolin, bentonite powder and diatomite are ground and crushed into composite powder, after activation and silane treatment, form double bond site, with the copolymerization site, with the ammonium polyphosphate after being modified by acrylic acid copolymerization, form interpenetrating network structure, realize the fixation of flame retardant;Through flame-retardant interpenetrating network structure is immersed in ferric chloride, interpenetrating network structure allows iron ion to pass through, and 2,5-amino terephthalic acid on the surface of composite powder occurs coordination, in-situ generates iron metal skeleton, improves the overall strength and porous adsorption of flame-retardant functional filler, and in the generation process of iron metal skeleton, phosphoric acid in ammonium polyphosphate can replace part of iron ion in iron-based MOF, impurity ion doping can fill skeleton hole, cause skeleton lattice distortion, produce more active sites, improve the ability of iron-based MOF catalytic carbon.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically a high-performance gypsum-based composite material and its preparation method. Background Technology

[0002] Compared to traditional concrete buildings, steel structure buildings use steel plates or steel sections instead of reinforced concrete, resulting in higher strength, better earthquake resistance, and shorter construction cycles. At the same time, the reusability of steel greatly reduces construction waste, making it more environmentally friendly. Therefore, steel structure buildings are widely used in industrial and civil buildings.

[0003] Steel used in steel structure buildings is a non-combustible building material. However, the mechanical properties of steel decrease drastically at high temperatures, causing it to lose its load-bearing capacity and undergo significant deformation. This leads to bending of steel columns and beams, and properties such as yield point, tensile strength, and modulus of elasticity all decrease sharply with increasing temperature. Therefore, steel structure materials must undergo fireproofing treatment to improve the fire resistance limit of the steel structure. A commonly used fireproofing method is to spray fire-retardant coatings onto the surface of the steel structure. At high temperatures, the fire-retardant coating forms a fire-resistant and heat-insulating layer, thereby improving the fire resistance limit of the steel structure.

[0004] Most fire-retardant coatings on the market use organic solvents as dispersion media, which results in the generation of a large amount of volatile organic compounds during the spraying process. This not only pollutes the environment but also harms the health of construction workers. Chinese Patent Announcement No. CN115073118B discloses a gypsum-based flame-retardant composite material and its preparation method. The composite material includes a first component and a second component. The first component, by weight, includes the following materials: 50 parts gypsum, 5 parts fiber, 60 parts sodium carbonate, 3 parts graphite, 3 parts sodium α-olefin sulfonate, 5 parts gypsum retarder, 2.5 parts nano-silica, 2.5 parts fly ash, and 2 parts dicalcium silicate. The second component, by weight, includes the following materials: 45 parts aluminum hydroxide powder, 5 parts isocyanate-terminated phosphorus-based organic flame retardant, and 5 parts flame-retardant microspheres. However, this method uses aluminum hydroxide and phosphorus-based organic flame retardant, which have a large difference in polarity. The hydroxyl groups on the surface of the inorganic particles and the ester groups of the organic flame retardant lack chemical bonding. Physical mixing alone can easily lead to interfacial separation. Under humid and hot conditions, the organic flame retardant is more likely to migrate to the surface, resulting in a reduction in the flame-retardant effect. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance gypsum-based composite material and its preparation method. Kaolin, bentonite powder and diatomaceous earth are ground and pulverized into composite powder. After activation and silane treatment, double bond sites are formed. These polymerization sites are then copolymerized with ammonium polyphosphate modified with acrylic acid to form an interpenetrating network structure, thereby fixing the flame retardant.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a high-performance gypsum-based composite material includes the following steps: Step 1: Grind and pulverize kaolin, bentonite powder and diatomaceous earth to obtain composite powder, and then wash with hydrochloric acid solution to obtain activated composite powder.

[0007] Step 2: Graft the activated composite powder with 2,5-aminoterephthalic acid to obtain a modified composite powder, and then treat it with γ-methacryloyloxypropyltrimethoxysilane to obtain a functionally modified composite powder.

[0008] Step 3: Modify ammonium polyphosphate with acrylic acid to obtain modified ammonium polyphosphate, and then copolymerize it with functional modified composite powder to obtain a flame-retardant interpenetrating network structure.

[0009] Step 4: Impregnate the flame-retardant interpenetrating network structure into iron salts, and obtain flame-retardant functional filler through hydrothermal reaction. Then, mix it with gypsum, sodium carbonate and gypsum retarder to obtain a high-performance gypsum-based composite material.

[0010] Furthermore, the ratio of gypsum, sodium carbonate, flame-retardant functional filler, and gypsum retarder is 60-70 parts: 20-30 parts: 10-15 parts: 4-6 parts.

[0011] Furthermore, the specific preparation steps of the composite powder are as follows: Kaolin, bentonite powder, and diatomaceous earth were mixed in a mass ratio of 1-2:1-2:1-2, then ground to obtain a composite powder. The composite powder and a 3M hydrochloric acid solution were added to a reaction vessel in a ratio of 3-4 kg:1-2 L. The mixture was stirred at 100-120℃ and 50-60 r / min for 6-7 h. After filtration, the filter cake was washed with deionized water and anhydrous ethanol until the final washing liquid was neutral. The mixture was then vacuum dried at 100-110℃ for 10-12 h to obtain the activated composite powder.

[0012] Furthermore, the specific preparation steps of the modified composite powder are as follows: The activated composite powder, 2,5-aminoterephthalic acid, and deionized water were added to a reaction vessel and stirred for 1-2 hours at 20-25℃ and 500-600 r / min. Then, N,N'-dicyclohexylcarbodiimide was added, and stirring was continued for 1-2 hours. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 hours to obtain the modified composite powder.

[0013] Furthermore, the ratio of activated composite powder, 2,5-aminoterephthalic acid, deionized water, and N,N'-dicyclohexylcarbodiimide is 2-3 kg: 800-900 g: 5-6 L: 40-50 mL.

[0014] Furthermore, the specific preparation steps of the functional modified composite powder are as follows: The modified composite powder, anhydrous ethanol, and deionized water were added to a reaction vessel and stirred for 20-30 minutes at 50-60℃ and 500-600 r / min. Then, γ-methacryloyloxypropyltrimethoxysilane was added, and the pH was adjusted to 3-4 with hydrochloric acid solution. The reaction was continued for 6-7 hours. After filtration, the precipitate was washed 2-4 times with deionized water and anhydrous ethanol and dried under vacuum at 60-70℃ for 1-2 hours to obtain the functional modified composite powder.

[0015] Furthermore, the ratio of modified composite powder, anhydrous ethanol, deionized water and γ-methacryloyloxypropyltrimethoxysilane is 1-2 kg: 800-900 mL: 1-2 L: 500-600 mL.

[0016] Furthermore, the specific preparation steps for modified ammonium polyphosphate are as follows: Acrylic acid, ammonium polyphosphate, and deionized water were added to a reaction vessel and stirred for 1-2 hours at 20-25°C and 500-600 r / min. Then, N,N'-dicyclohexylcarbodiimide and hydroquinone as a polymerization inhibitor were added, and stirring was continued for 1-2 hours. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70°C for 1-2 hours to obtain modified ammonium polyphosphate.

[0017] Furthermore, the ratio of acrylic acid, ammonium polyphosphate, deionized water, N,N'-dicyclohexylcarbodiimide, and hydroquinone is 400-500mL: 250-260g: 4-5L: 40-50mL: 25-30g.

[0018] Furthermore, the specific preparation steps of the flame-retardant interpenetrating network structure are as follows: The functional modified composite powder, modified ammonium polyphosphate, and deionized water were added to a reaction vessel, and nitrogen gas was introduced for protection. The mixture was stirred at 95-100℃ and 500-600 r / min for 1-2 h. After cooling to 55-65℃, sodium persulfate as an initiator and hydroxymethylacrylamide as a crosslinking agent were added to the reaction vessel. The mixture was heated to 70-80℃ and stirred at 500-600 r / min for 3-4 h. After filtration, the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively, and then vacuum dried at 60-70℃ for 1-2 h to obtain a flame-retardant interpenetrating network structure.

[0019] Furthermore, the ratio of the amount of functional modified composite powder, modified ammonium polyphosphate, deionized water, sodium persulfate and hydroxymethylacrylamide is 1-2 kg: 200-220 g: 3-4 L: 12-14 g: 13-15 g.

[0020] Furthermore, the specific preparation steps for the flame-retardant functional filler are as follows: Flame-retardant interpenetrating network structure and deionized water are added to a polytetrafluoroethylene reactor and stirred for 20-30 min at 20-25℃ and 500-600 r / min. Then, a mixed solution of sodium hexadecyl sulfate and 50-60 wt% ethanol solution is added, heated to 120-130℃, and stirred for another 20-30 min. Ferric chloride is then added, and the mixture is impregnated under a vacuum of -0.085 MPa for 4-5 h. Stirring continues for 24-26 h, followed by filtration. The filter cake is washed 2-4 times with deionized water and anhydrous ethanol, and then vacuum dried at 60-70℃ for 1-2 h to obtain the flame-retardant functional filler.

[0021] Furthermore, the ratio of flame-retardant interpenetrating network structure, deionized water, sodium hexadecyl sulfate, ethanol solution and ferric chloride is 1-2 kg: 2-3 L: 15-17 g: 120-140 mL: 250-300 g.

[0022] The beneficial effects of this invention are: 1. The high-performance gypsum-based composite material prepared by the present invention is obtained by mixing gypsum, sodium carbonate, flame-retardant functional filler and gypsum retarder, and has excellent strength, toughness and flame retardancy.

[0023] 2. The flame-retardant functional filler of the present invention is prepared by grinding kaolin, bentonite powder and diatomaceous earth into a composite powder, grafting it with 2,5-aminoterephthalic acid to obtain a modified composite powder, and then treating it with γ-methacryloyloxypropyltrimethoxysilane to obtain a functional modified composite powder containing double bonds. Ammonium polyphosphate is modified with acrylic acid to give it double bonds on its surface, and then copolymerized with the functional modified composite powder to obtain a flame-retardant interpenetrating network structure. The formation of the interpenetrating network structure can improve the strength of the flame-retardant functional filler, and the cross-linking structure of the interpenetrating network structure can fix the ammonium polyphosphate in the cross-linking network, preventing the ammonium polyphosphate from migrating during long-term use.

[0024] 3. The flame-retardant functional filler of the present invention is impregnated in ferric chloride through a flame-retardant interpenetrating network structure. The interpenetrating network structure allows iron ions to pass through and coordinate with 2,5-aminoterephthalic acid on the surface of the composite powder to generate an iron metal skeleton in situ. The formation of the skeleton can improve the overall strength and porous adsorption of the flame-retardant functional filler. In addition, during the formation of the iron metal skeleton, the phosphoric acid in the ammonium polyphosphate can replace some of the iron ions in the iron-based MOF. The doping of impurity ions can fill the skeleton vacancies, neutralize the charge and expand the interlayer spacing, resulting in lattice distortion of the skeleton, generating more active sites and improving the ability of the iron-based MOF to catalyze carbon formation. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: A method for preparing a high-performance gypsum-based composite material, comprising the following steps: S1: Mix 1 kg of kaolin, 1 kg of bentonite powder and 1 kg of diatomaceous earth, grind and pulverize to obtain composite powder; add 3 kg of composite powder and 1 L of 3M hydrochloric acid solution to a reaction vessel, stir for 6 h at 100℃ and 50 r / min, filter, wash the filter cake with deionized water and anhydrous ethanol until the last washing liquid is neutral, and vacuum dry at 100℃ for 10 h to obtain activated composite powder.

[0027] S2: Add 2 kg of activated composite powder, 800 g of 2,5-aminoterephthalic acid and 5 L of deionized water to a reaction vessel, stir for 1 h at 20 °C and 500 r / min, then add 40 mL of N,N'-dicyclohexylcarbodiimide, continue stirring for 1 h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry under vacuum at 60 °C for 1 h to obtain modified composite powder.

[0028] S3: Add 1 kg of modified composite powder, 800 mL of anhydrous ethanol and 1 L of deionized water to a reaction vessel, stir for 20 min at 50 °C and 500 r / min, then add 500 mL of γ-methacryloyloxypropyltrimethoxysilane, adjust the pH to 3 with hydrochloric acid solution, continue stirring for 6 h, filter, wash the precipitate twice with deionized water and anhydrous ethanol, and vacuum dry at 60 °C for 1 h to obtain the functional modified composite powder.

[0029] S4: Add 400 mL of acrylic acid, 250 g of ammonium polyphosphate and 4 L of deionized water to a reactor and stir for 1 h at 20 °C and 500 r / min. Then add 40 mL of N,N'-dicyclohexylcarbodiimide and 25 g of hydroquinone as a polymerization inhibitor and continue stirring for 1 h. Filter the mixture and wash the filter cake twice with deionized water and anhydrous ethanol, respectively. Dry the cake under vacuum at 60 °C for 1 h to obtain modified ammonium polyphosphate.

[0030] S5: Add 1 kg of functional modified composite powder, 200 g of modified ammonium polyphosphate and 3 L of deionized water to a reactor, purge with nitrogen for protection, and stir at 95 °C and 500 r / min for 1 h. Cool to 55 °C, add 12 g of sodium persulfate as an initiator and 13 g of hydroxymethylacrylamide as a crosslinking agent to the reactor, heat to 70 °C, stir at 500 r / min for 3 h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and vacuum dry at 60 °C for 1 h to obtain a flame-retardant interpenetrating network structure.

[0031] S6: Add 1 kg of flame-retardant interpenetrating network structure and 2 L of deionized water to a polytetrafluoroethylene reactor. Stir for 20 min at 20 °C and 500 r / min. Then add a mixed solution of 15 g of sodium hexadecyl sulfate and 120 mL of 50 wt% ethanol solution. Heat to 120 °C and continue stirring for 20 min. Then add 250 g of ferric chloride and impregnate for 4 h under a vacuum of -0.085 MPa. Continue stirring for 24 h. Filter and wash the filter cake twice with deionized water and anhydrous ethanol, respectively. Dry under vacuum at 60 °C for 1 h to obtain the flame-retardant functional filler.

[0032] S7: Mix 60 parts of gypsum, 20 parts of sodium carbonate, 10 parts of flame-retardant functional filler and 4 parts of gypsum retarder to obtain a high-performance gypsum-based composite material.

[0033] Example 2: A method for preparing a high-performance gypsum-based composite material, comprising the following steps: S1: Mix 1.5 kg of kaolin, 1.5 kg of bentonite powder and 1.5 kg of diatomaceous earth, grind and pulverize to obtain composite powder; add 3.5 kg of composite powder and 1.5 L of 3M hydrochloric acid solution to a reaction vessel, stir for 6.5 h at 110 °C and 55 r / min, filter, wash the filter cake with deionized water and anhydrous ethanol until the last washing liquid is neutral, and vacuum dry at 105 °C for 11 h to obtain activated composite powder.

[0034] S2: Add 2.5 kg of activated composite powder, 850 g of 2,5-aminoterephthalic acid and 5.5 L of deionized water to a reaction vessel and stir for 1.5 h at 22.5 °C and 550 r / min. Then add 45 mL of N,N'-dicyclohexylcarbodiimide and continue stirring for 1.5 h. Filter and wash the filter cake three times with deionized water and anhydrous ethanol, respectively. Dry under vacuum at 65 °C for 1.5 h to obtain the modified composite powder.

[0035] S3: Add 1.5 kg of modified composite powder, 850 mL of anhydrous ethanol and 1.5 L of deionized water to a reaction vessel, stir for 25 min at 55 °C and 550 r / min, then add 550 mL of γ-methacryloyloxypropyltrimethoxysilane, adjust the pH to 3.5 with hydrochloric acid solution, continue stirring for 6.5 h, filter, wash the precipitate three times with deionized water and anhydrous ethanol, and vacuum dry at 65 °C for 1.5 h to obtain the functional modified composite powder.

[0036] S4: Add 450 mL of acrylic acid, 255 g of ammonium polyphosphate and 4.5 L of deionized water to a reactor and stir for 1.5 h at 22.5 °C and 550 r / min. Then add 45 mL of N,N'-dicyclohexylcarbodiimide and 27.5 g of hydroquinone as a polymerization inhibitor and continue stirring for 1.5 h. Filter and wash the filter cake three times with deionized water and anhydrous ethanol, respectively. Dry under vacuum at 65 °C for 1.5 h to obtain modified ammonium polyphosphate.

[0037] S5: Add 1.5 kg of functional modified composite powder, 210 g of modified ammonium polyphosphate and 3.5 L of deionized water to a reactor, purge with nitrogen for protection, and stir at 97.5 °C and 550 r / min for 1.5 h. Cool to 60 °C, add 13 g of sodium persulfate as an initiator and 14 g of hydroxymethylacrylamide as a crosslinking agent to the reactor, heat to 75 °C and stir at 550 r / min for 3.5 h, filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and vacuum dry at 65 °C for 1.5 h to obtain a flame-retardant interpenetrating network structure.

[0038] S6: Add 1.5 kg of flame-retardant interpenetrating network structure and 2.5 L of deionized water to a polytetrafluoroethylene reactor. Stir for 25 min at 22.5 °C and 550 r / min. Then add a mixed solution of 16 g of sodium hexadecyl sulfate and 130 mL of 55 wt% ethanol solution. Heat to 125 °C and continue stirring for 25 min. Then add 275 g of ferric chloride. Impregnate for 4.5 h under a vacuum of -0.085 MPa. Continue stirring for 25 h. Filter and wash the filter cake three times with deionized water and anhydrous ethanol, respectively. Dry under vacuum at 65 °C for 1.5 h to obtain the flame-retardant functional filler.

[0039] S7: Mix 65 parts of gypsum, 25 parts of sodium carbonate, 12.5 parts of flame-retardant filler and 5 parts of gypsum retarder to obtain a high-performance gypsum-based composite material.

[0040] Example 3: A method for preparing a high-performance gypsum-based composite material, comprising the following steps: S1: Mix 2 kg of kaolin, 2 kg of bentonite powder and 2 kg of diatomaceous earth, grind and pulverize to obtain composite powder; add 4 kg of composite powder and 2 L of 3M hydrochloric acid solution to a reaction vessel, stir for 7 h at 120℃ and 60 r / min, filter, wash the filter cake with deionized water and anhydrous ethanol until the last washing liquid is neutral, and vacuum dry at 110℃ for 12 h to obtain activated composite powder.

[0041] S2: Add 3 kg of activated composite powder, 900 g of 2,5-aminoterephthalic acid and 6 L of deionized water to a reaction vessel, stir for 2 h at 25 °C and 600 r / min, then add 50 mL of N,N'-dicyclohexylcarbodiimide, continue stirring for 2 h, filter, wash the filter cake 4 times with deionized water and anhydrous ethanol respectively, and vacuum dry at 70 °C for 2 h to obtain modified composite powder.

[0042] S3: Add 2 kg of modified composite powder, 900 mL of anhydrous ethanol and 2 L of deionized water to a reaction vessel, stir for 30 min at 60 °C and 600 r / min, then add 600 mL of γ-methacryloyloxypropyltrimethoxysilane, adjust the pH to 4 with hydrochloric acid solution, continue stirring for 7 h, filter, wash the precipitate 4 times with deionized water and anhydrous ethanol, and vacuum dry at 70 °C for 2 h to obtain the functional modified composite powder.

[0043] S4: Add 500 mL of acrylic acid, 260 g of ammonium polyphosphate and 5 L of deionized water to a reactor and stir for 2 h at 25 °C and 600 r / min. Then add 50 mL of N,N'-dicyclohexylcarbodiimide and 30 g of hydroquinone as a polymerization inhibitor and continue stirring for 2 h. Filter the mixture and wash the filter cake four times with deionized water and anhydrous ethanol, respectively. Dry the cake under vacuum at 70 °C for 2 h to obtain modified ammonium polyphosphate.

[0044] S5: Add 2 kg of functional modified composite powder, 220 g of modified ammonium polyphosphate and 4 L of deionized water to a reactor, purge with nitrogen for protection, and stir at 100 °C and 600 r / min for 2 h. Cool to 65 °C, add 14 g of sodium persulfate as an initiator and 15 g of hydroxymethylacrylamide as a crosslinking agent to the reactor, heat to 80 °C, stir at 600 r / min for 4 h, filter, wash the filter cake with deionized water and anhydrous ethanol 4 times respectively, and vacuum dry at 70 °C for 2 h to obtain a flame-retardant interpenetrating network structure.

[0045] S6: Add 2 kg of flame-retardant interpenetrating network structure and 3 L of deionized water to a polytetrafluoroethylene reactor. Stir for 30 min at 25 °C and 600 r / min. Then add a mixed solution of 17 g of sodium hexadecyl sulfate and 140 mL of 60 wt% ethanol solution. Heat to 130 °C and continue stirring for 30 min. Then add 300 g of ferric chloride and impregnate for 5 h under a vacuum of -0.085 MPa. Continue stirring for 26 h. Filter and wash the filter cake 4 times with deionized water and anhydrous ethanol respectively. Dry under vacuum at 70 °C for 2 h to obtain the flame-retardant functional filler.

[0046] S7: Mix 70 parts of gypsum, 30 parts of sodium carbonate, 15 parts of flame-retardant functional filler and 6 parts of gypsum retarder to obtain a high-performance gypsum-based composite material.

[0047] Comparative Example 1: Based on Example 3, the functional modified composite powder in step S3 was replaced with the modified composite powder in step S2.

[0048] Comparative Example 2: Based on Example 3, the modified ammonium polyphosphate in step S4 was replaced with ammonium polyphosphate.

[0049] Comparative Example 3: Based on Example 3, the flame-retardant interpenetrating network structure in step S5 was replaced with a mixture of functional modified composite powder and modified ammonium polyphosphate in a mass ratio of 2:220.

[0050] Comparative Example 4: Based on Example 3, without the processing in step S6, the flame-retardant interpenetrating network structure in step S5 is directly used as the flame-retardant functional filler in step S7.

[0051] The performance of the high-performance gypsum-based composite materials obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to the national standard GB14907-2018 "Fireproof Coatings for Steel Structures". The results are shown in Table 1. Table 1 ; As can be seen from Table 1, the bonding strength, compressive strength, dry density and fire resistance of the high-performance gypsum-based composite materials obtained in Examples 1-3 are significantly better than those of the comparative examples, indicating that the high-performance gypsum-based composite materials prepared by the present invention have excellent strength, toughness and flame retardancy.

[0052] In Comparative Example 1, the functional modified composite powder was replaced with the modified composite powder from step S2. The silane coupling agent grafted with γ-methacryloyloxypropyltrimethoxysilane without step S3 resulted in a lack of carbon-carbon double bonds on the powder surface, preventing free radical copolymerization with the modified ammonium polyphosphate. This prevented the formation of an interpenetrating network, causing the flame retardant to exist only as a physical mixture. The reinforcing effect of the interpenetrating network structure disappeared, the compressive strength of the filler decreased, and the ammonium polyphosphate, not being fixed by the cross-linked network, easily precipitated upon contact with water, leading to long-term flame retardancy failure.

[0053] In Comparative Example 2, the modified ammonium polyphosphate was replaced with ammonium polyphosphate without acrylic acid modification. The surface of ammonium polyphosphate has no reactive double bonds and is highly hydrophilic, making it unable to copolymerize with the functional modified composite powder. The interpenetrating network structure breaks down, and the hydrophilicity leads to poor compatibility with the gypsum matrix interface, making it easy to aggregate and form stress concentration points. In a humid and hot environment, ammonium polyphosphate hydrolyzes rapidly, and the solution expands in volume after absorbing moisture, causing microcracks in the gypsum matrix and reducing compressive strength.

[0054] In Comparative Example 3, the flame-retardant interpenetrating network structure was replaced with a mixture of functional modified composite powder and modified ammonium polyphosphate in a 2:220 mass ratio. Only the functional modified powder and modified APP were mechanically mixed, without a chemically cross-linked IPN network, resulting in uneven dispersion of the flame retardant. The hydroxymethylacrylamide cross-linking agent did not participate in the reaction, and the material lacked three-dimensional network support, making it impossible to form a continuous expanding char layer during combustion.

[0055] In Comparative Example 4, the flame-retardant interpenetrating network structure was directly used as a flame-retardant functional filler. The impregnation with ferric chloride can coordinate with 2,5-aminoterephthalic acid on the surface of the composite powder to generate an iron metal framework in situ. During the formation of the iron metal framework, the phosphoric acid in ammonium polyphosphate can replace some of the iron ions in the iron-based MOF. The doping of impurity ions can fill the framework holes, neutralize the charge and expand the interlayer spacing, resulting in lattice distortion of the framework, generating more active sites and improving the ability of the iron-based MOF to catalyze carbon formation.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a high-performance gypsum-based composite material, characterized in that, Includes the following steps: Step 1: Grind and pulverize kaolin, bentonite powder and diatomaceous earth to obtain composite powder, and then wash with hydrochloric acid solution to obtain activated composite powder; Step 2: Graft the activated composite powder with 2,5-aminoterephthalic acid to obtain a modified composite powder, and then treat it with γ-methacryloyloxypropyltrimethoxysilane to obtain a functional modified composite powder. Step 3: Modify ammonium polyphosphate with acrylic acid to obtain modified ammonium polyphosphate, and then copolymerize it with functional modified composite powder to obtain a flame-retardant interpenetrating network structure; Step 4: Impregnate the flame-retardant interpenetrating network structure into iron salts, and obtain flame-retardant functional filler through hydrothermal reaction. Then, mix it with gypsum, sodium carbonate and gypsum retarder to obtain a high-performance gypsum-based composite material.

2. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The ratio of gypsum, sodium carbonate, flame-retardant functional filler and gypsum retarder is 60-70 parts: 20-30 parts: 10-15 parts: 4-6 parts.

3. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The specific preparation steps of the composite powder are as follows: Kaolin, bentonite powder, and diatomaceous earth were mixed in a mass ratio of 1-2:1-2:1-2, then ground to obtain a composite powder. The composite powder and a 3M hydrochloric acid solution were added to a reaction vessel in a ratio of 3-4 kg:1-2 L. The mixture was stirred at 100-120℃ and 50-60 r / min for 6-7 h. After filtration, the filter cake was washed with deionized water and anhydrous ethanol until the final washing liquid was neutral. The mixture was then vacuum dried at 100-110℃ for 10-12 h to obtain the activated composite powder.

4. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The specific preparation steps of the modified composite powder are as follows: The activated composite powder, 2,5-aminoterephthalic acid and deionized water were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 1-2 h. Then N,N'-dicyclohexylcarbodiimide was added and stirring was continued for 1-2 h. The mixture was filtered, washed and vacuum dried to obtain the modified composite powder. The ratio of the activated composite powder, 2,5-aminoterephthalic acid, deionized water, and N,N'-dicyclohexylcarbodiimide is 2-3 kg: 800-900 g: 5-6 L: 40-50 mL.

5. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The specific preparation steps of the functionally modified composite powder are as follows: The modified composite powder, anhydrous ethanol and deionized water were added to a reaction vessel and stirred for 20-30 min at 50-60℃ and 500-600 r / min. Then γ-methacryloyloxypropyltrimethoxysilane was added, and the pH value was adjusted to 3-4 with hydrochloric acid solution. The reaction was continued to be stirred for 6-7 h. The mixture was then filtered, washed, and vacuum dried to obtain the functional modified composite powder. The ratio of the modified composite powder, anhydrous ethanol, deionized water and γ-methacryloyloxypropyltrimethoxysilane is 1-2 kg: 800-900 mL: 1-2 L: 500-600 mL.

6. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The specific preparation steps for the modified ammonium polyphosphate are as follows: Acrylic acid, ammonium polyphosphate and deionized water were added to a reaction vessel and stirred for 1-2 hours at 20-25℃ and 500-600 r / min. Then N,N'-dicyclohexylcarbodiimide and hydroquinone were added and stirred for another 1-2 hours. The mixture was then filtered, washed and dried under vacuum to obtain modified ammonium polyphosphate. The ratio of acrylic acid, ammonium polyphosphate, deionized water, N,N'-dicyclohexylcarbodiimide, and hydroquinone is 400-500 mL: 250-260 g: 4-5 L: 40-50 mL: 25-30 g.

7. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The specific preparation steps of the flame-retardant interpenetrating network structure are as follows: The functional modified composite powder, modified ammonium polyphosphate, and deionized water were added to a reaction vessel, and nitrogen gas was introduced for protection. The mixture was stirred at 95-100℃ and 500-600 r / min for 1-2 h. After cooling to 55-65℃, sodium persulfate and hydroxymethylacrylamide were added to the reaction vessel, and the mixture was heated to 70-80℃ and stirred at 500-600 r / min for 3-4 h. The mixture was then filtered, washed, and vacuum dried to obtain a flame-retardant interpenetrating network structure.

8. The method for preparing a high-performance gypsum-based composite material according to claim 7, characterized in that, The ratio of the functional modified composite powder, modified ammonium polyphosphate, deionized water, sodium persulfate and hydroxymethylacrylamide is 1-2 kg: 200-220 g: 3-4 L: 12-14 g: 13-15 g.

9. The method for preparing a high-performance gypsum-based composite material according to claim 1, characterized in that, The specific preparation steps for the flame-retardant functional filler are as follows: Flame-retardant interpenetrating network structure and deionized water are added to a polytetrafluoroethylene reactor and stirred for 20-30 min at 20-25℃ and 500-600 r / min. Then, a mixed solution of sodium hexadecyl sulfate and 50-60 wt% ethanol solution is added, heated to 120-130℃, and stirred for another 20-30 min. Ferric chloride is then added, and the mixture is impregnated under a vacuum of -0.085 MPa for 4-5 h. The mixture is then stirred for another 24-26 h, filtered, washed, and vacuum dried to obtain the flame-retardant functional filler. The ratio of the flame-retardant interpenetrating network structure, deionized water, sodium hexadecyl sulfate, ethanol solution and ferric chloride is 1-2 kg: 2-3 L: 15-17 g: 120-140 mL: 250-300 g.

10. A high-performance gypsum-based composite material, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.