Modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material, preparation method and application thereof

Abstract

The present application relates to the technical field of gypsum-based composite material, in particular to a modified plant fiber reinforced temperature and humidity adjusting gypsum-based composite material, a preparation method and application thereof, comprising the following steps: S1. mixing desulfurization gypsum, modified phase change microcapsules, modified humidity adjusting material, fly ash, ordinary Portland cement, modified plant fiber, silica ash and graphite, stirring until mixed uniformly to obtain dry mixture; S2. mixing calcium hydroxide, citric acid, polycarboxylate superplasticizer and water, stirring until mixed uniformly to obtain wet mixture; S3. slowly adding the wet mixture into the dry mixture, stirring at low speed for 2-4 min, then stirring at high speed for 1-3 min, pouring into a mold, vibrating and exhausting, standing and then demolding, and standard curing to obtain the modified plant fiber reinforced temperature and humidity adjusting gypsum-based composite material. The present application simultaneously utilizes three kinds of wastes, i.e. desulfurization gypsum, fly ash and crop straw, as main raw materials, so that the raw materials are widely sourced and low in cost, and the preparation process is simple and low in energy consumption.

Description

Technical Field

[0001] This invention relates to the field of gypsum-based composite materials technology, specifically to a modified plant fiber reinforced temperature and humidity-regulating gypsum-based composite material, its preparation method, and its application. Background Technology

[0002] Research on building indoor environmental control materials mainly focuses on single temperature or humidity control functions. Building energy consumption accounts for more than 45% of my country's total energy consumption, with HVAC systems accounting for more than 50% of building operating energy consumption. Traditional decorative materials are mostly heat and humidity inert materials, lacking the ability to autonomously regulate ambient temperature and humidity, and heavily relying on active air conditioning systems, resulting in huge energy consumption. Therefore, developing new building materials with passive temperature and humidity control functions is of great significance for reducing building energy consumption.

[0003] Regarding gypsum-based materials, desulfurized gypsum, a major industrial solid waste generated from flue gas desulfurization in coal-fired power plants (annual output exceeding 80 million tons, with a utilization rate of less than 50%), is primarily composed of calcium sulfate dihydrate. After calcination, it can be converted into hemihydrate gypsum, exhibiting excellent cementing properties. Its resource utilization in building material preparation is of significant value for solid waste reduction and the development of green building materials. However, desulfurized gypsum-based materials suffer from inherent defects such as low mechanical strength and poor water resistance.

[0004] In the field of temperature control, phase change energy storage gypsum board utilizes the latent heat of solid-liquid phase change to regulate temperature by incorporating phase change materials (PCMs), making it the most promising passive temperature control technology currently available. Porous mineral materials such as diatomaceous earth, zeolite, and sepiolite are widely used for humidity control due to their rich pore structure and surface adsorption properties. Existing humidity-regulating materials are mostly composites with gypsum in the form of coatings or additives, possessing only a single humidity-regulating function and lacking temperature regulation capabilities, thus failing to achieve coordinated temperature and humidity control.

[0005] To address the limitations of single-function materials, integrated temperature and humidity control materials have emerged in recent years. However, existing integrated temperature and humidity control materials generally neglect the synergistic design of mechanical properties. The introduction of functional components often comes at the cost of matrix strength, resulting in brittle materials prone to cracking, failing to meet the mechanical performance and durability requirements of practical engineering projects. Straw fiber is widely available and biodegradable; incorporating it into the composite matrix can form a three-dimensional network support structure, improving toughness and crack resistance.

[0006] There is currently no known method for preparing composite materials that uses desulfurized gypsum as a matrix to organically integrate phase change temperature regulation, porous material moisture storage and regulation, and alkali treatment-modified straw fiber mechanical reinforcement, thereby achieving integrated temperature and humidity regulation and mechanical properties. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material includes the following preparation steps: S1. By weight, mix 60-100 parts of desulfurized gypsum, 40-60 parts of modified phase change microcapsules, 20-60 parts of modified moisture-regulating material, 8-18 parts of fly ash, 12-18 parts of ordinary silicate cement, 2-6 parts of modified plant fiber, 4-10 parts of silica fume, and 4-10 parts of graphite, and stir at a speed of 100-150 r / min until the mixture is uniform to obtain a dry mix. S2. Mix 2-10 parts calcium hydroxide, 0.2-0.4 parts citric acid, 0.6-2.4 parts polycarboxylate superplasticizer with 42-50 parts water, and stir at 200-300 r / min until the mixture is uniform to obtain a wet mixture; S3. Slowly add the wet mixture obtained in step S2 to the dry mixture obtained in step S1. Stir at 80-100 r / min for 2-4 min, then stir at 200-300 r / min for 1-3 min. Pour into a mold, vibrate to remove air, let stand for 22-24 h, then demold and cure according to standard to obtain the modified plant fiber reinforced temperature and humidity gypsum-based composite material.

[0009] The preparation of modified humidity-regulating materials includes the following steps: S11. By weight, 35-40 parts of diatomaceous earth, 25-30 parts of white zeolite, 15-20 parts of sepiolite, 8-10 parts of attapulgite and 5-8 parts of activated alumina are placed in a ball mill and ball-milled at a speed of 250-300 r / min for 20-30 min. After passing through a 200-mesh sieve, a mixed powder is obtained. S12. Add the mixed powder obtained in step S11 to 180-200 parts of a 5% lithium chloride aqueous solution, stir and impregnate at 200-250 r / min for 1-2 hours under a water bath at 58-60℃, filter, and dry at 100-105℃ for 1-2 hours to obtain the preliminary modified powder. S13. Mix the preliminary modified powder obtained in step S12, 230-250 parts of anhydrous ethanol and 1.3-1.5 parts of titanate coupling agent, ultrasonically disperse at a frequency of 40kHz for 10-15min, stir and reflux at 78-80℃ for 50-60min, filter and vacuum dry at 78-80℃ for 3-4h to obtain the secondary modified powder; S14. Place the modified mixture obtained in step S13 into a muffle furnace, heat it to 380-400℃ at a rate of 5℃ / min, hold it at that temperature for 1-2 hours, and then cool it naturally to obtain the modified humidity-regulating material.

[0010] Preferably, the preparation of modified plant fibers includes the following steps: S21. Place straw raw material with an aspect ratio of 7-7.5 in a 3% sodium hydroxide solution and soak it in a water bath at 68-70℃ for 3-5 minutes. Rinse it with distilled water until neutral, then remove it and dry it to obtain straw fiber. (Step S21 is to break down the waxy and siliceous layers on the surface of the straw fiber, increase the roughness of the fiber surface, and improve the interfacial adhesion between the fiber and the matrix material.) S22. Place the straw fiber in the modified enzyme solution, soak it in a water bath at 42-45℃ for 30-90 minutes, rinse it with distilled water until neutral, remove it, and air dry it in a ventilated place; (Step S22 is to selectively remove organic impurities such as pectin and hemicellulose from the surface of the straw fiber, further increase the active groups on the fiber surface, and improve the compatibility between the fiber and the inorganic matrix) S23. After drying the straw fibers in step S22, immerse them in an organosilicon waterproofing agent at room temperature for 2-4 minutes, then remove them and air dry them naturally in a ventilated place to obtain modified plant fibers. (The purpose of step S23 is to form a hydrophobic protective film on the surface of the straw fibers, effectively preventing the fibers from absorbing moisture and expanding, and improving the dimensional stability and durability of the composite material in a humid environment.) Preferably, the preparation of modified phase change microcapsules includes the following steps: S31. By weight, mix 80-100 parts of fly ash cenospheres with 80-100 parts of acidic etching solution, stir continuously at room temperature for 1-2 hours, let stand, and then take off the lower layer of cenospheres to obtain pretreated cenospheres. S32. Add the pretreated microspheres and 250-300 parts of paraffin wax into a vacuum chamber, and continuously evacuate the vacuum chamber for 1-2 hours under a negative pressure of -0.8MPa. Rinse the excess paraffin wax remaining on the surface of the microspheres with warm water, then rinse with cold water, and finally air dry naturally at room temperature in the dark and ventilated conditions to obtain phase change microspheres. S33. Add the phase change microspheres to a silica sol with a mass concentration of 25%, impregnate at room temperature and stir slowly for 20-30 minutes, and air dry naturally in a cool, ventilated environment without direct sunlight to finally obtain modified phase change microcapsules.

[0011] Preferably, the preparation of the modified enzyme solution includes the following steps: S221. Dissolve 0.3-0.5 parts sodium dihydrogen phosphate and 0.7-1 parts disodium hydrogen phosphate in 60-70 parts deionized water by weight, and adjust the pH to 8.9-9.1 to obtain a buffer base solution; S222. Under stirring conditions of 100-150 r / min, add 0.3-0.6 parts alkaline protease, 0.5-0.8 parts pectinase, 0.1-0.2 parts cellulase, 0.2-0.4 parts Tween-80, and 0.5-0.8 parts glycerol, and continue stirring until completely dissolved; S223. Add 40-50 parts of deionized water to the solution obtained in step S222, continue stirring for 10-15 minutes, and let it stand at 4°C for 25-30 minutes to finally obtain the modified enzyme solution.

[0012] Preferably, the standard curing temperature is 18-22℃, the relative humidity is 45-55%, and the time is 24-28 days.

[0013] Preferably, the straw raw material is selected from one or more combinations of corn straw, wheat straw, rice straw or sorghum straw.

[0014] Preferably, the acidic etching solution consists of a 1.2 mol / L NH4F solution and a 1.0 mol / L HCl solution, with a volume ratio of 1:1.

[0015] Preferably, in step S33, the volume ratio of phase change microspheres to silica sol with a mass concentration of 25% is 1:3.

[0016] A modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material was prepared by the above preparation method.

[0017] Application of a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material in building materials.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes modified phase change microcapsules to reversibly absorb or release a large amount of latent heat through solid-liquid phase change within their phase change temperature range, endowing the material with high thermal inertia. Simultaneously, modified plant fibers form a three-dimensional interwoven network within the gypsum matrix, effectively reducing the thermal conductivity of the composite material and delaying heat transfer. The synergistic effect of these two factors enables the composite material to possess "passive" temperature regulation capabilities, significantly reducing the amplitude of outdoor temperature fluctuations transferred to the interior, lowering the building's air conditioning load, and achieving energy conservation and emission reduction.

[0019] 2. This invention utilizes the rich mesoporous structure and strongly hydrophilic active surface of the modified humidity-regulating material to reversibly absorb and release moisture according to changes in relative humidity, automatically adjusting indoor humidity to a comfortable range for the human body. At the same time, this active humidity-regulating function effectively inhibits the risk of moisture absorption and expansion, biodegradation, and mold growth of the modified plant fibers in high-humidity environments. Furthermore, the desulfurized gypsum matrix itself is weakly alkaline, further providing an antibacterial and anti-corrosion chemical environment for the modified plant fibers, thereby significantly improving the long-term durability and safety of the composite material.

[0020] 3. The modified plant fiber of this invention serves as a reinforcing component. Its fiber structure can form a three-dimensional network support structure within the desulfurized gypsum matrix, playing a bridging and reinforcing role. This significantly improves the flexural strength of the composite material. Through synergistic action with the modified enzyme solution, it further increases the active groups on the fiber surface, improving the compatibility between the fiber and the inorganic matrix (gypsum matrix). After surface modification treatment with the modified enzyme solution, the strength can be further enhanced, effectively improving the inherent defects of desulfurized gypsum, such as high brittleness, easy cracking, and poor impact resistance. At the same time, the modified phase change microcapsules can fill the pores inside the matrix and work synergistically with the modified plant fiber to improve temperature regulation performance while ensuring that the compressive and flexural strength of the composite material meets the requirements for use in building masonry, plastering, etc., thus extending the service life of the material.

[0021] 4. This invention simultaneously utilizes three major wastes—desulfurized gypsum (industrial solid waste), fly ash (industrial solid waste), and crop straw (agricultural solid waste)—as main raw materials. Not only are the raw materials widely available and inexpensive, but the preparation process is also simple and energy-efficient. After the product's life cycle ends, it can be naturally degraded or crushed and reused, achieving a unity of "waste treatment" and high-value functional utilization, which aligns with the development orientation of green building materials and circular economy. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for preparing the modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material of the present invention; Figure 2 This is a flow chart of the preparation process of the modified humidity-regulating material of the present invention; Figure 3 This is a flowchart illustrating the preparation process of the modified plant fiber of this invention. Figure 4 This is a process flow diagram for preparing the modified phase change microcapsules of the present invention; Figure 5 This is a flow chart of the preparation process of the modified enzyme solution of the present invention; Figure 6 The image shows the DSC test results of the modified phase change microcapsules obtained in Example 1 of this invention. Detailed Implementation

[0023] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Please see Figures 1-6 The present invention provides a technical solution: Example 1 A method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material: Before preparing the modified plant fiber-reinforced temperature and humidity-regulating gypsum-based composite material, the following steps are taken: Preparation of modified enzyme solution, modified humidity-regulating material, modified plant fiber, and modified phase change microcapsules are performed: The preparation of the modified enzyme solution includes the following steps: S221. Dissolve 0.3g sodium dihydrogen phosphate and 0.7g disodium hydrogen phosphate in 60g deionized water, adjust the pH to 8.9, and obtain a buffer base solution; S222. Under stirring conditions of 100 r / min, add 0.3 g alkaline protease, 0.5 g pectinase, 0.1 g cellulase, 0.2 g Tween-80, and 0.5 g glycerol, and continue stirring until completely dissolved; S223. Add 40g of deionized water to the solution obtained in step S222, continue stirring for 10min, and let it stand at 4℃ for 25min to finally obtain the modified enzyme solution.

[0025] The preparation of modified humidity-regulating materials includes the following steps: S11. Place 35g of diatomaceous earth, 25g of white zeolite, 15g of sepiolite, 8g of attapulgite and 5g of activated alumina in a ball mill and ball mill at 250r / min for 20min. After passing through a 200-mesh sieve, a mixed powder is obtained. S12. Add the mixed powder obtained in step S11 to 180g of lithium chloride aqueous solution with a mass concentration of 5%, stir and impregnate at 200r / min for 1h under water bath conditions at 58℃, filter and dry at 100℃ for 1h to obtain the preliminary modified powder. S13. The pre-modified powder obtained in step S12, 230g of anhydrous ethanol and 1.3g of titanate coupling agent are mixed, ultrasonically dispersed at a frequency of 40kHz for 10min, stirred and refluxed at 78℃ for 50min, filtered and vacuum dried at 78℃ for 3h to obtain the second-step modified powder. S14. Place the modified mixture obtained in step S13 into a muffle furnace, heat it to 380°C at a rate of 5°C / min, hold it at that temperature for 1 hour, and then cool it naturally to obtain the modified humidity-regulating material.

[0026] The preparation of modified plant fibers includes the following steps: S21. Place corn stalks with an aspect ratio of 7 in a 3% sodium hydroxide solution and soak them in a water bath at 68°C for 3 minutes. Rinse them with distilled water until neutral, then remove them and dry them to obtain straw fibers. S22. Place the straw fiber in the modified enzyme solution, soak it in a water bath at 42°C for 30 minutes, rinse it with distilled water until neutral, take it out, and let it air dry in a ventilated place. S23. After drying the straw fibers in step S22, soak them in an organosilicon waterproofing agent at room temperature for 2 minutes, then remove them and air dry them naturally in a ventilated place to obtain modified plant fibers.

[0027] The preparation of modified phase change microcapsules includes the following steps: S31. Mix 80g of fly ash cenospheres with 80g of acidic etching solution (composed of 1.2mol / L NH4F solution and 1.0mol / L HCl solution, with a volume ratio of 1:1), stir continuously at room temperature for 1h, let stand, and then take off the lower layer of cenospheres to obtain pretreated cenospheres. S32. Add the pretreated microbeads and 250g of paraffin wax into a vacuum chamber, and continuously vacuum for 1 hour under a negative pressure of -0.8MPa. Rinse the excess paraffin wax remaining on the surface of the microbeads with warm water, then rinse with cold water, and finally air dry naturally at room temperature in the dark and ventilated conditions to obtain phase change microbeads. S33. Add the phase change microspheres to a silica sol with a mass concentration of 25% (volume ratio of 1:3), impregnate at room temperature and stir slowly for 20 minutes, and air dry naturally in a cool, ventilated environment without direct sunlight to finally obtain modified phase change microcapsules.

[0028] The preparation of modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials includes the following steps: S1. Mix 60g desulfurized gypsum, 40g modified phase change microcapsules, 20g modified moisture-regulating material, 8g fly ash, 12g ordinary silicate cement, 2g modified plant fiber, 4g silica fume, and 4g graphite, and stir at 100r / min until the mixture is uniform to obtain a dry mix. S2. Mix 2g calcium hydroxide, 0.2g citric acid, 0.6g polycarboxylate superplasticizer with 42g water, and stir at 200r / min until the mixture is uniform to obtain a wet mixture; S3. Slowly add the wet mixture obtained in step S2 to the dry mixture obtained in step S1. Stir at 80 r / min for 2 min, then stir at 200 r / min for 1 min. Pour into a mold, vibrate to remove air, let stand for 22 h, then demold and cure under standard conditions (temperature 18℃, relative humidity 45%, time 24 days) to obtain the modified plant fiber reinforced temperature and humidity gypsum-based composite material.

[0029] Example 2 A method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material: Before preparing the modified plant fiber-reinforced temperature and humidity-regulating gypsum-based composite material, the following steps are taken: Preparation of modified enzyme solution, modified humidity-regulating material, modified plant fiber, and modified phase change microcapsules are performed: The preparation of the modified enzyme solution includes the following steps: S221. Dissolve 0.5g sodium dihydrogen phosphate and 1g disodium hydrogen phosphate in 70g deionized water, adjust the pH to 9.1, and obtain a buffer base solution; S222. Under stirring conditions of 150 r / min, add 0.6 g alkaline protease, 0.8 g pectinase, 0.2 g cellulase, 0.4 g Tween-80, and 0.8 g glycerol, and continue stirring until completely dissolved; S223. Add 50g of deionized water to the solution obtained in step S222, continue stirring for 15min, and let it stand at 4℃ for 30min to finally obtain the modified enzyme solution.

[0030] The preparation of modified humidity-regulating materials includes the following steps: S11. Place 40g of diatomaceous earth, 30g of white zeolite, 20g of sepiolite, 10g of attapulgite and 8g of activated alumina in a ball mill and ball mill at 300r / min for 30min. After passing through a 200-mesh sieve, a mixed powder is obtained. S12. Add the mixed powder obtained in step S11 to 200g of lithium chloride aqueous solution with a mass concentration of 5%, stir and impregnate at 250r / min for 2h under 60℃ water bath conditions, filter and dry at 105℃ for 2h to obtain preliminary modified powder. S13. The pre-modified powder obtained in step S12, 250g of anhydrous ethanol and 1.5g of titanate coupling agent are mixed, ultrasonically dispersed at a frequency of 40kHz for 15min, stirred and refluxed at 80℃ for 60min, filtered and vacuum dried at 80℃ for 4h to obtain the second-step modified powder. S14. Place the modified mixture obtained in step S13 into a muffle furnace, heat it to 400°C at a rate of 5°C / min, hold it at that temperature for 2 hours, and then cool it naturally to obtain the modified humidity-regulating material.

[0031] The preparation of modified plant fibers includes the following steps: S21. Wheat straw with an aspect ratio of 7.5 is placed in a 3% sodium hydroxide solution and soaked in a water bath at 70°C for 5 minutes. After rinsing with distilled water until neutral, it is taken out and dried to obtain straw fiber. S22. Place the straw fiber in the modified enzyme solution, soak it in a water bath at 45°C for 90 minutes, rinse it with distilled water until neutral, take it out, and let it air dry in a ventilated place. S23. After drying the straw fibers in step S22, soak them in an organosilicon waterproofing agent at room temperature for 4 minutes, then remove them and air dry them naturally in a ventilated place to obtain modified plant fibers.

[0032] The preparation of modified phase change microcapsules includes the following steps: S31. Mix 100g of fly ash cenospheres with 100g of acidic etching solution (composed of 1.2mol / L NH4F solution and 1.0mol / L HCl solution, with a volume ratio of 1:1), stir continuously at room temperature for 2h, let stand, and then take off the lower layer of cenospheres to obtain pretreated cenospheres. S32. Add the pretreated microbeads and 300g of paraffin wax into a vacuum chamber, and continuously vacuum for 2 hours under a negative pressure of -0.8MPa. Rinse the excess paraffin wax remaining on the surface of the microbeads with warm water, then rinse with cold water, and finally air dry naturally at room temperature in the dark and ventilated conditions to obtain phase change microbeads. S33. Add the phase change microspheres to a silica sol with a mass concentration of 25% (volume ratio of 1:3), impregnate at room temperature and stir slowly for 30 minutes, and air dry naturally in a cool, ventilated environment without direct sunlight to finally obtain modified phase change microcapsules.

[0033] The preparation of modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials includes the following steps: S1. Mix 100g desulfurized gypsum, 60g modified phase change microcapsules, 60g modified moisture-regulating material, 18g fly ash, 18g ordinary silicate cement, 6g modified plant fiber, 10g silica fume, and 10g graphite, and stir at 150r / min until the mixture is uniform to obtain a dry mix. S2. Mix 10g calcium hydroxide, 0.4g citric acid, 2.4g polycarboxylate superplasticizer with 50g water, and stir at 300r / min until the mixture is uniform to obtain a wet mixture; S3. Slowly add the wet mixture obtained in step S2 to the dry mixture obtained in step S1. Stir at 100 r / min for 4 min, then stir at 300 r / min for 3 min. Pour into a mold, vibrate to remove air, let stand for 24 h, then demold and cure under standard conditions (temperature 22℃, relative humidity 55%, time 28 days) to obtain the modified plant fiber reinforced temperature and humidity gypsum-based composite material.

[0034] Example 3 A method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material: Before preparing the modified plant fiber-reinforced temperature and humidity-regulating gypsum-based composite material, the following steps are taken: Preparation of modified enzyme solution, modified humidity-regulating material, modified plant fiber, and modified phase change microcapsules are performed: The preparation of the modified enzyme solution includes the following steps: S221. Dissolve 0.4g sodium dihydrogen phosphate and 0.8g disodium hydrogen phosphate in 65g deionized water, adjust the pH to 9, and obtain a buffer base solution; S222. Under stirring conditions of 120 r / min, add 0.5 g alkaline protease, 0.6 g pectinase, 0.15 g cellulase, 0.3 g Tween-80, and 0.6 g glycerol, and continue stirring until completely dissolved; S223. Add 45g of deionized water to the solution obtained in step S222, continue stirring for 12min, and let it stand at 4℃ for 26min to finally obtain the modified enzyme solution.

[0035] The preparation of modified humidity-regulating materials includes the following steps: S11. Place 36g of diatomaceous earth, 27g of white zeolite, 17g of sepiolite, 7g of attapulgite and 6g of activated alumina in a ball mill and ball mill at 280r / min for 25min. After passing through a 200-mesh sieve, a mixed powder is obtained. S12. Add the mixed powder obtained in step S11 to 190g of lithium chloride aqueous solution with a mass concentration of 5%, stir and impregnate at 220r / min for 1.5h under water bath conditions at 59℃, filter and dry at 102℃ for 1.5h to obtain the preliminary modified powder. S13. The pre-modified powder obtained in step S12, 240g of anhydrous ethanol and 1.4g of titanate coupling agent are mixed, ultrasonically dispersed at a frequency of 40kHz for 12min, stirred and refluxed at 79℃ for 55min, filtered and vacuum dried at 79℃ for 3.5h to obtain the secondary modified powder. S14. Place the modified mixture obtained in step S13 into a muffle furnace, heat it to 390°C at a rate of 5°C / min, hold it at that temperature for 1.5 hours, and then cool it naturally to obtain the modified humidity-regulating material.

[0036] The preparation of modified plant fibers includes the following steps: S21. Rice straw with an aspect ratio of 7.3 was placed in a 3% sodium hydroxide solution and soaked in a water bath at 69°C for 4 minutes. After rinsing with distilled water until neutral, the straw was removed and dried to obtain straw fiber. S22. Place the straw fiber in the modified enzyme solution, soak it in a water bath at 43°C for 60 minutes, rinse it with distilled water until neutral, take it out, and let it air dry in a ventilated place. S23. After drying the straw fibers in step S22, soak them in an organosilicon waterproofing agent at room temperature for 3 minutes, then remove them and air dry them naturally in a ventilated place to obtain modified plant fibers.

[0037] The preparation of modified phase change microcapsules includes the following steps: S31. Mix 90g of fly ash cenospheres with 90g of acidic etching solution (composed of 1.2mol / L NH4F solution and 1.0mol / L HCl solution, with a volume ratio of 1:1), stir continuously at room temperature for 1.5h, let stand, and then take off the lower layer of cenospheres to obtain pretreated cenospheres. S32. Add the pretreated microspheres and 260g of paraffin wax into a vacuum chamber, and continuously evacuate for 1.5h under a negative pressure of -0.8MPa. Rinse the excess paraffin wax remaining on the surface of the microspheres with warm water, then rinse with cold water, and finally air dry naturally at room temperature in the dark and ventilated conditions to obtain phase change microspheres. S33. Add the phase change microspheres to a silica sol with a mass concentration of 25% (volume ratio of 1:3), impregnate at room temperature and stir slowly for 25 minutes, and air dry naturally in a cool, ventilated environment without direct sunlight to finally obtain modified phase change microcapsules.

[0038] The preparation of modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials includes the following steps: S1. Mix 70g desulfurized gypsum, 50g modified phase change microcapsules, 30g modified moisture-regulating material, 11g fly ash, 14g ordinary silicate cement, 4g modified plant fiber, 6g silica fume, and 6g graphite, and stir at 120r / min until the mixture is uniform to obtain a dry mix. S2. Mix 5g calcium hydroxide, 0.3g citric acid, 1.2g polycarboxylate superplasticizer with 45g water, and stir at 250r / min until the mixture is uniform to obtain a wet mixture; S3. Slowly add the wet mixture obtained in step S2 to the dry mixture obtained in step S1. Stir at 90 r / min for 3 min, then stir at 250 r / min for 2 min. Pour into a mold, vibrate to remove air, let stand for 23 h, then demold and cure under standard conditions (temperature 20℃, relative humidity 50%, time 26 days) to obtain the modified plant fiber reinforced temperature and humidity gypsum-based composite material.

[0039] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no modified humidity-regulating material was added in this comparative example; the other steps are exactly the same in Comparative Example 1 and Example 1.

[0040] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that no modified plant fiber was added in this comparative example; the other steps are exactly the same in Comparative Example 2 and Example 1.

[0041] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that no modified phase change microcapsules were added in this comparative example; the other steps are exactly the same in Comparative Example 3 and Example 1.

[0042] Performance testing: The phase change performance of the modified phase change microcapsules obtained in Example 1 was tested by differential scanning calorimetry. Figure 6The image shows the DSC test results of the modified phase change microcapsules obtained in Example 1 of this invention. The experiment was conducted under N2 atmosphere protection, with a heating and cooling rate of 5 K / min within a temperature range of 0°C to 50°C. The DSC test results show that the modified phase change microcapsules exhibit a significant melting endothermic peak in the range of 11.9-23.8°C, with a melting enthalpy of 71.0 J / g; and a significant crystallization exothermic peak in the range of 5.7-9.9°C, with a crystallization enthalpy of 73.7 J / g. The close values ​​of the melting and crystallization enthalpies indicate that the modified phase change microcapsules possess good heat storage-exothermic reversibility. Phase change enthalpy reflects the material's ability to absorb or release latent heat during phase change. When the ambient temperature rises to the melting temperature range, the phase change core material in the modified phase change microcapsules undergoes a solid-liquid phase change and absorbs heat, thus reducing the rate of temperature rise of the composite material; when the ambient temperature drops to the crystallization temperature range, the phase change core material undergoes a liquid-solid phase change and releases heat, thus reducing the rate of temperature fall of the composite material. Therefore, the higher the phase change enthalpy, the more heat a unit mass of material can absorb or release within the phase change temperature range, and the more significant the peak-shaving, delaying, and buffering effect on indoor temperature fluctuations. The phase change enthalpy data shows that the phase change component in the composite material of this invention can provide a significant contribution to latent heat storage, indicating that the temperature regulation effect of the composite material does not solely depend on changes in thermal conductivity, but mainly originates from the endothermic and exothermic behavior of the modified phase change microcapsules during the phase change process. Higher melting enthalpy and crystallization enthalpy indicate that a unit mass of material can absorb or release more heat within the phase change temperature range, and its buffering capacity against temperature fluctuations is stronger.

[0043] The compressive and flexural strengths of the modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar". A 40mm×40mm×160mm prism mold was used. The flexural strength (three-point bending) of the obtained gypsum-based composite materials was first measured using a cement mortar flexural and compressive strength testing machine, and then the compressive strength was measured using a block tester. The loading rate was 2.4 kN / s.

[0044] The apparent density of the modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T 5486-2008 "Test Methods for Inorganic Rigid Thermal Insulation Products". A 40mm×40mm×160mm prism mold was used to weigh the dry mass of the gypsum-based composite material, measure its volume, and calculate its density.

[0045] The thermal conductivity of the modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials". The tests were conducted using a steady-state heat flow meter thermal conductivity meter at an average temperature of 25±2℃ and a temperature difference of 20℃ between the hot and cold plates.

[0046] The moisture regulation properties (moisture absorption / release) of the modified plant fiber reinforced temperature and humidity regulating gypsum-based composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to JIS A 1470-1:2014 "Test Method for Moisture Absorption / Release Properties of Building Materials". Under moisture absorption conditions, the temperature was 23℃, RH=95%, and the storage time was 7 days; under moisture release conditions, the temperature was 23℃, RH=30%, and the storage time was 7 days. The moisture absorption and release amounts were calculated. The results are shown in Table 1 below: Table 1. Performance Test Results As shown in Table 1, the modified plant fiber-reinforced temperature and humidity regulating gypsum-based composite materials obtained in Examples 1-3 outperform the comparative examples in all aspects. The superior mechanical properties indicate that the modified plant fibers form a three-dimensional network support structure within the gypsum matrix, playing a significant bridging and reinforcing role. This effectively improves the brittleness and cracking issues of the desulfurized gypsum matrix; without the modified plant fibers, the material's toughness decreases significantly. The data in Table 1 demonstrate that the synergistic effect of the modified plant fibers and modified phase change microcapsules enables the composite material to possess "passive" temperature regulation capabilities, significantly reducing the amplitude of outdoor temperature fluctuations transmitted indoors, lowering the building's air conditioning load, and achieving energy conservation and emission reduction. The modified humidity regulating material imparts a reversible moisture absorption capacity of 8.7-9.1% to the composite material, enabling passive regulation of indoor humidity and improving the long-term durability and safety of the composite material.

[0047] 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 alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material, characterized in that, The preparation steps include the following: S1. By weight, mix 60-100 parts of desulfurized gypsum, 40-60 parts of modified phase change microcapsules, 20-60 parts of modified moisture-regulating material, 8-18 parts of fly ash, 12-18 parts of ordinary silicate cement, 2-6 parts of modified plant fiber, 4-10 parts of silica fume, and 4-10 parts of graphite, and stir at a speed of 100-150 r / min until the mixture is uniform to obtain a dry mix. S2. Mix 2-10 parts calcium hydroxide, 0.2-0.4 parts citric acid, 0.6-2.4 parts polycarboxylate superplasticizer with 42-50 parts water, and stir at 200-300 r / min until the mixture is uniform to obtain a wet mixture; S3. Slowly add the wet mixture obtained in step S2 to the dry mixture obtained in step S1. Stir at 80-100 r / min for 2-4 min, then stir at 200-300 r / min for 1-3 min. Pour into a mold, vibrate to remove air, let stand for 22-24 h, then demold and cure according to standard to obtain the modified plant fiber reinforced temperature and humidity regulated gypsum-based composite material. The preparation of the modified humidity-regulating material includes the following steps: S11. By weight, 35-40 parts of diatomaceous earth, 25-30 parts of white zeolite, 15-20 parts of sepiolite, 8-10 parts of attapulgite and 5-8 parts of activated alumina are placed in a ball mill and ball-milled at a speed of 250-300 r / min for 20-30 min. After passing through a 200-mesh sieve, a mixed powder is obtained. S12. Add the mixed powder obtained in step S11 to 180-200 parts of a 5% lithium chloride aqueous solution, stir and impregnate at 200-250 r / min for 1-2 hours under a water bath at 58-60℃, filter, and dry at 100-105℃ for 1-2 hours to obtain the preliminary modified powder. S13. Mix the preliminary modified powder obtained in step S12, 230-250 parts of anhydrous ethanol and 1.3-1.5 parts of titanate coupling agent, ultrasonically disperse at a frequency of 40kHz for 10-15min, stir and reflux at 78-80℃ for 50-60min, filter and vacuum dry at 78-80℃ for 3-4h to obtain the secondary modified powder; S14. Place the modified mixture obtained in step S13 into a muffle furnace, heat it to 380-400℃ at a rate of 5℃ / min, hold it at that temperature for 1-2 hours, and then cool it naturally to obtain the modified humidity-regulating material.

2. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 1, characterized in that, The preparation of the modified plant fiber includes the following steps: S21. Place straw raw materials with an aspect ratio of 7-7.5 in a 3% sodium hydroxide solution and soak them in a water bath at 68-70℃ for 3-5 minutes. Rinse them with distilled water until neutral, then remove and dry them to obtain straw fiber. S22. Place the straw fiber in the modified enzyme solution, soak it in a water bath at 42-45℃ for 30-90 minutes, rinse it with distilled water until neutral, take it out, and let it air dry in a ventilated place. S23. After drying the straw fibers in step S22, soak them in an organosilicon waterproofing agent at room temperature for 2-4 minutes, then remove them and air dry them naturally in a ventilated place to obtain modified plant fibers.

3. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 1, characterized in that, The preparation of the modified phase change microcapsules includes the following steps: S31. By weight, mix 80-100 parts of fly ash cenospheres with 80-100 parts of acidic etching solution, stir continuously at room temperature for 1-2 hours, let stand, and then take off the lower layer of cenospheres to obtain pretreated cenospheres. S32. Add the pretreated microspheres and 250-300 parts of paraffin wax into a vacuum chamber, and continuously evacuate the vacuum chamber for 1-2 hours under a negative pressure of -0.8MPa. Rinse the excess paraffin wax remaining on the surface of the microspheres with warm water, then rinse with cold water, and finally air dry naturally at room temperature in the dark and ventilated conditions to obtain phase change microspheres. S33. Add the phase change microspheres to a silica sol with a mass concentration of 25%, impregnate at room temperature and stir slowly for 20-30 minutes, and air dry naturally in a cool, ventilated environment without direct sunlight to finally obtain modified phase change microcapsules.

4. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 2, characterized in that, The preparation of the modified enzyme solution includes the following steps: S221. Dissolve 0.3-0.5 parts sodium dihydrogen phosphate and 0.7-1 parts disodium hydrogen phosphate in 60-70 parts deionized water by weight, and adjust the pH to 8.9-9.1 to obtain a buffer base solution; S222. Under stirring conditions of 100-150 r / min, add 0.3-0.6 parts alkaline protease, 0.5-0.8 parts pectinase, 0.1-0.2 parts cellulase, 0.2-0.4 parts Tween-80, and 0.5-0.8 parts glycerol, and continue stirring until completely dissolved; S223. Add 40-50 parts of deionized water to the solution obtained in step S222, continue stirring for 10-15 minutes, and let it stand at 4°C for 25-30 minutes to finally obtain the modified enzyme solution.

5. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 1, characterized in that, The standard curing temperature is 18-22℃, the relative humidity is 45-55%, and the time is 24-28 days.

6. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 2, characterized in that, The straw raw material is selected from one or more combinations of corn straw, wheat straw, rice straw or sorghum straw.

7. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 3, characterized in that, The acidic etching solution consists of a 1.2 mol / L NH4F solution and a 1.0 mol / L HCl solution, with a volume ratio of 1:

1.

8. The method for preparing a modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 3, characterized in that, In step S33, the volume ratio of phase change microspheres to silica sol with a mass concentration of 25% is 1:

3.

9. A modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

10. The application of the modified plant fiber reinforced temperature and humidity regulating gypsum-based composite material according to claim 9 in building materials.

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