A heat-insulating material with fire-resistant and heat-insulating properties and its manufacturing method

Abstract

The present application relates to thermal insulation material technical field, disclose a kind of thermal insulation material with fireproof heat insulation characteristics and its manufacturing method, the thermal insulation material includes: construct multilayer gradient phase change heat storage structure, form biomineralization inorganic framework, set high temperature activation self-repair system and plant fiber and attapulgite composite reinforcement.The present application significantly prolongs material fireproof time by multiple protection mechanisms, has self-repairing ability after fire, effectively solves the technical problems such as insufficient fire resistance of traditional fireproof heat insulation material, structure damage is not repairable and phase change material is easy to lose, especially suitable for industrial plant fireproof wall, tunnel inner wall fireproof heat insulation layer, petrochemical equipment protection layer and other high fire risk environment.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, and more specifically, to a thermal insulation material with fireproof and heat-insulating properties and its manufacturing method. Background Technology

[0002] Thermal insulation materials are widely used in construction, industry, and daily life. Their main function is to reduce heat transfer and maintain temperature stability. With technological advancements, thermal insulation materials are constantly being innovated and developed, but traditional fire-resistant and heat-insulating materials still face the following major technical challenges:

[0003] Traditional thermal insulation materials mainly rely on increasing the gas phase porosity and reducing the thermal conductivity to achieve thermal insulation. However, their thermal insulation performance decreases significantly in high-temperature fire environments. Traditional phase change thermal storage materials are prone to loss after melting, resulting in reduced thermal insulation effect. Single phase change materials are difficult to cope with complex temperature environments and cannot achieve efficient fireproof and thermal insulation under different temperature gradients. Existing thermal insulation materials often suffer structural integrity damage and significantly reduced thermal insulation performance after high-temperature fires, which is difficult to recover, greatly limiting their service life and safety. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a heat-insulating material with fire-resistant and heat-insulating properties and a method for manufacturing the same.

[0005] A heat-insulating material with fireproof and heat-insulating properties, the heat-insulating material comprising a multi-layer gradient phase change heat storage structure with melting points gradually increasing from the outside to the inside, a biomineralized inorganic skeleton, and a high-temperature activated self-healing system;

[0006] The multi-layer gradient phase change thermal storage structure includes an outer layer, a middle layer, and an inner layer. The outer layer uses a low-melting-point phase change material with a melting point of 60-120℃, the middle layer uses a medium-melting-point phase change material with a melting point of 200-350℃, and the inner layer uses a high-melting-point phase change material with a melting point of 350-450℃.

[0007] The biomineralized inorganic framework is formed by silicate and carbonate deposition and is transformed into a ceramic phase at high temperature, which restricts the liquid flow of the phase change material.

[0008] The high-temperature activated self-healing system includes a self-healing precursor compound pre-placed in the biomineralized inorganic framework. The precursor compound is activated under high-temperature fire conditions and reacts with the surrounding mineralized framework to form a ceramic phase, thereby repairing structural damage to the material.

[0009] Preferably, the low-melting-point phase change material, the medium-melting-point phase change material, and the high-melting-point phase change material are selected from inorganic hydrated salts, organic phase change materials, or composite phase change materials, respectively.

[0010] The inorganic hydrated salt includes sodium sulfate decahydrate and sodium chloride;

[0011] The organic phase change material includes hexadecane and paraffin;

[0012] The composite phase change materials include expanded graphite / paraffin composite materials and modified montmorillonite / sodium sulfate composite materials.

[0013] Preferably, the biomineralized inorganic framework is formed through the following steps:

[0014] Sodium silicate solution and calcium chloride solution were mixed at a molar ratio of 1:1.2, a mineralization inducer was added, and the pH was adjusted to 8.0-8.5 to obtain a biomineralization reaction solution.

[0015] The pretreated plant fibers and some phase change materials are immersed in the mineralization reaction solution and stirred at 30-40°C for 12-24 hours to form calcium silicate deposition.

[0016] Adding sodium carbonate solution to the system forms a composite mineralization layer of calcium carbonate deposition;

[0017] The inorganic framework structure is stabilized by drying at 90-100℃ for 8-12 hours, followed by heat treatment at 200-250℃ for 2 hours.

[0018] Preferably, the self-healing precursor compound comprises a low-temperature activated precursor, a medium-temperature activated precursor, and a high-temperature activated precursor that are sequentially activated at different temperatures;

[0019] The low-temperature activated precursor is activated at 300-400℃, the medium-temperature activated precursor is activated at 500-600℃, and the high-temperature activated precursor is activated at 700-800℃.

[0020] Preferably, the low-temperature activation precursor is aluminum phosphate, the medium-temperature activation precursor is aluminum borate, and the high-temperature activation precursor is aluminum hydroxide.

[0021] Preferably, the thermal insulation material further includes a composite reinforcement system of plant fibers and attapulgite.

[0022] The plant fibers are activated by alkali treatment, pretreated by high-temperature carbonization, and grafted with surface functional groups. The attapulgite clay is activated by interlayer ion exchange, organic modification, and heat treatment.

[0023] Preferably, the plant fiber is selected from flax fiber, bamboo fiber or straw fiber; the surface functional group grafting treatment grafts carboxyl, hydroxyl or amino functional groups onto the surface of the plant fiber.

[0024] Preferably, the interlayer ion exchange of the attapulgite soil uses aluminum ion solution and magnesium ion solution, and the organic modification uses quaternary ammonium salt modifier or organosilane coupling agent.

[0025] A method for preparing a thermal insulation material with fire-resistant and heat-insulating properties includes the following steps:

[0026] Step 1: Raw material preparation;

[0027] Step 2: Plant fiber pretreatment;

[0028] Step 3: Attapulgite modification treatment;

[0029] Step 4: Construction of biomineralized inorganic framework;

[0030] Step 5: Composite of multilayer gradient phase change materials;

[0031] Step 6: Construction of the high-temperature activation self-healing system;

[0032] Step 7: Molding and Curing;

[0033] Step 8: Performance testing and quality control.

[0034] Preferably, the molding and curing in step 7 adopts a pressure molding process, with the pressure controlled at 15-20 MPa. After molding, the material is dried at 80-120℃ for 12-24 hours, followed by heat treatment at 150-200℃ for 4-6 hours to complete the curing process.

[0035] The beneficial effects of this invention are as follows:

[0036] Fire and thermal insulation performance: Through a multi-layered gradient phase change heat storage structure, the material provides effective thermal insulation protection at 800℃, extending the fire resistance time by more than 50% compared to traditional materials. Specifically, when the outer surface temperature of the material reaches 800℃, the inner surface temperature can still be maintained below 150℃ for 20 minutes, while the inner surface temperature of traditional materials will rapidly rise to above 300℃ under the same conditions. Thermal conductivity test results show that the thermal conductivity of this material is 0.06-0.08 W / (m·K), which is lower than most commercial fire and thermal insulation materials (typical value is 0.10-0.15 W / (m·K)).

[0037] Self-healing function: After being damaged by fire, the material repairs structural defects through a high-temperature activated self-healing system, maintaining 70-80% of its original thermal insulation performance after a single fire, while traditional materials typically fail completely and require replacement. This function extends the material's lifespan and improves safety and reliability.

[0038] Stability of phase change materials: The biomineralized inorganic framework, modified attapulgite, and plant fiber network work together to solve the problem of easy loss of traditional phase change materials after melting. After multiple thermal cycles, the loss rate of phase change materials does not exceed 5%, maintaining the long-term thermal insulation performance of the materials.

[0039] Temperature adaptability: The multi-layer gradient structure enables the material to adapt to a wide temperature range of 60-800℃, which solves the limitations of traditional single phase change materials in complex temperature environments and is suitable for various fire scenarios.

[0040] Environmental friendliness: It uses natural renewable plant fibers, attapulgite and other environmentally friendly materials, which reduces the dependence on petroleum-based materials and meets the requirements of green building and sustainable development.

[0041] Wide range of applications: Suitable for protective systems in high-fire-risk environments, such as firewalls in industrial plants, fire-resistant and heat-insulating layers for tunnel walls, and protective layers for petrochemical equipment. The material provides everyday thermal insulation while offering protection and self-healing capabilities in the event of a fire. Attached Figure Description

[0042] Figure 1 These are microscopic images comparing the crack state of sample A before and after repair;

[0043] Figure 2 These are microscopic images comparing the crack state of sample B before and after repair.

[0044] Figure 3 These are microscopic images comparing the crack state of sample C before and after repair;

[0045] Figure 4 These are microscopic images comparing the crack state of sample D before and after repair;

[0046] Figure 5 It is a comparison of the performance recovery rates of each sample;

[0047] Figure 6 These are the internal temperature distribution curves of different samples at an external surface temperature of 600℃.

[0048] Figure 7 It is a comparison of the temperature transfer rates of various samples at different temperatures;

[0049] Figure 8 It represents the change in the cumulative loss rate of phase change material in each sample during the thermal cycling process. Detailed Implementation

[0050] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0051] Example 1

[0052] This embodiment proposes a heat insulation material with fireproof and heat insulation properties. The heat insulation material includes a multi-layer gradient phase change heat storage structure with melting points gradually increasing from the outside to the inside, a biomineralized inorganic skeleton, and a high-temperature activated self-healing system.

[0053] The multi-layer gradient phase change thermal storage structure includes an outer layer, a middle layer, and an inner layer. The outer layer uses a low-melting-point phase change material with a melting point of 90℃, the middle layer uses a medium-melting-point phase change material with a melting point of 275℃, and the inner layer uses a high-melting-point phase change material with a melting point of 400℃.

[0054] Low-melting-point phase change materials, medium-melting-point phase change materials, and high-melting-point phase change materials are selected from inorganic hydrated salts, organic phase change materials, or composite phase change materials, respectively.

[0055] Among them, inorganic hydrated salts include sodium sulfate decahydrate and sodium chloride;

[0056] Organic phase change materials include hexadecane and paraffin;

[0057] Composite phase change materials include expanded graphite / paraffin composites and modified montmorillonite / sodium sulfate composites.

[0058] Biomineralized inorganic frameworks are formed through silicate and carbonate deposition and are transformed into ceramic phases at high temperatures, restricting the liquid flow of phase change materials;

[0059] Biomineralized inorganic frameworks are formed through the following steps:

[0060] Sodium silicate solution and calcium chloride solution were mixed at a molar ratio of 1:1.2, a mineralization inducer was added, and the pH was adjusted to 8.2 to obtain a biomineralization reaction solution.

[0061] Pretreated plant fibers and some phase change materials were immersed in a mineralization reaction solution and stirred at 35°C for 18 hours to form calcium silicate deposition.

[0062] Adding sodium carbonate solution to the system forms a composite mineralization layer of calcium carbonate deposition;

[0063] The inorganic framework structure was stabilized by drying at 95°C for 10 hours and then heat-treating at 225°C for 2 hours.

[0064] The high-temperature activated self-healing system includes a self-healing precursor compound pre-placed in a biomineralized inorganic framework. The precursor compound is activated under high-temperature fire conditions and reacts with the surrounding mineralized framework to form a ceramic phase, thus repairing material structural damage.

[0065] Self-healing precursor compounds include low-temperature activated precursors, medium-temperature activated precursors, and high-temperature activated precursors that are activated sequentially at different temperatures;

[0066] Among them, the low-temperature activated precursor is activated at 350℃, the medium-temperature activated precursor is activated at 550℃, and the high-temperature activated precursor is activated at 750℃.

[0067] The precursor for low-temperature activation is aluminum phosphate, the precursor for medium-temperature activation is aluminum borate, and the precursor for high-temperature activation is aluminum hydroxide.

[0068] The insulation material also includes a composite reinforcement system of plant fibers and attapulgite.

[0069] Among them, plant fibers are activated by alkali treatment, pretreated by high-temperature carbonization and treated by surface functional group grafting, and attapulgite is activated by interlayer ion exchange, organic modification and heat treatment.

[0070] The plant fiber is selected from flax fiber; the surface functional group grafting treatment grafts carboxyl functional groups onto the surface of the plant fiber;

[0071] Interlayer ion exchange of attapulgite was performed using aluminum ion solution and magnesium ion solution, and organic modification was performed using quaternary ammonium salt modifier.

[0072] Example 2

[0073] The difference between this embodiment and Embodiment 1 is that:

[0074] The multi-layer gradient phase change thermal storage structure includes an outer layer, a middle layer, and an inner layer. The outer layer uses a low-melting-point phase change material with a melting point of 60℃, the middle layer uses a medium-melting-point phase change material with a melting point of 200℃, and the inner layer uses a high-melting-point phase change material with a melting point of 350℃.

[0075] Biomineralized inorganic frameworks are formed through the following steps:

[0076] Sodium silicate solution and calcium chloride solution were mixed at a molar ratio of 1:1.2, a mineralization inducer was added, and the pH was adjusted to 8.0 to obtain a biomineralization reaction solution.

[0077] Pretreated plant fibers and some phase change materials were immersed in a mineralization reaction solution and stirred at 30°C for 12 hours to form calcium silicate deposition.

[0078] The inorganic framework structure was stabilized by drying at 90℃ for 8 hours and then heat-treating at 200℃ for 2 hours.

[0079] Low-temperature activated precursors are activated at 300℃, medium-temperature activated precursors are activated at 500℃, and high-temperature activated precursors are activated at 700℃.

[0080] The plant fiber is selected from bamboo fiber or; the surface functional group grafting treatment grafts hydroxyl functional groups onto the surface of the plant fiber.

[0081] Organic modification uses organosilane coupling agents.

[0082] Example 3

[0083] The difference between this embodiment and Embodiment 1 is that:

[0084] The multi-layer gradient phase change thermal storage structure includes an outer layer, a middle layer, and an inner layer. The outer layer uses a low-melting-point phase change material with a melting point of 120℃, the middle layer uses a medium-melting-point phase change material with a melting point of 350℃, and the inner layer uses a high-melting-point phase change material with a melting point of 450℃.

[0085] Biomineralized inorganic frameworks are formed through the following steps:

[0086] Sodium silicate solution and calcium chloride solution were mixed at a molar ratio of 1:1.2, a mineralization inducer was added, and the pH was adjusted to 8.5 to obtain a biomineralization reaction solution.

[0087] Pretreated plant fibers and some phase change materials were immersed in a mineralization reaction solution and stirred at 40°C for 24 hours to form calcium silicate deposition.

[0088] The inorganic framework structure was stabilized by drying at 100°C for 12 hours and then heat-treating at 250°C for 2 hours.

[0089] Low-temperature activated precursors are activated at 400℃, medium-temperature activated precursors are activated at 600℃, and high-temperature activated precursors are activated at 800℃.

[0090] The plant fiber is selected from straw fiber; the surface functional group grafting treatment grafts carboxyamino functional groups onto the surface of the plant fiber.

[0091] Example 4

[0092] This embodiment proposes a method for preparing a heat-insulating material with fire-resistant and heat-insulating properties, including the following steps:

[0093] Step 1: Raw Material Preparation

[0094] This step mainly involves preparing the following raw materials:

[0095] Phase change material composition: 3-5 types of phase change heat storage materials with different melting points (60℃, 120℃, 200℃, 350℃, 450℃) are used, including:

[0096] Inorganic hydrated salts: sodium sulfate decahydrate (Na2SO4·10H2O, melting point 32.4℃, latent heat of phase change 254 J / g), sodium chloride (NaCl, melting point 801℃, used in combination with hydrated water of crystallization);

[0097] Organic phase change materials: hexadecane (C 16 H 34 Melting point 18.2℃, latent heat of phase change 236 J / g), paraffin (C 20 -C40 Mixture, melting point range 50-60℃, latent heat of phase change 200-220 J / g);

[0098] Composite phase change materials: expanded graphite / paraffin composite material (mass ratio 1:4, melting point 58-62℃, thermal conductivity improved by 30%), modified montmorillonite / sodium sulfate composite material (mass ratio 1:3, leakage prevention effect improved by 50%).

[0099] The selection of phase change materials must meet the following technical parameters: latent heat of phase change ≥200 J / g, thermal stability (TGA test, mass loss ≤5% at 300℃), and cycle stability (phase change temperature shift ≤2℃ after 100 thermal cycles).

[0100] Biomineralization framework precursors: Prepare the following solutions as mineralization precursors:

[0101] Sodium silicate solution (Na2SiO3·9H2O, industrial grade, SiO2 content ≥26%): concentration 0.2-0.3mol / L, pH 10.5-11.5;

[0102] Calcium chloride solution (CaCl2·2H2O, analytical grade, purity ≥99%): concentration 0.24-0.36 mol / L, pH 6.5-7.5;

[0103] Sodium carbonate solution (Na2CO3, analytical grade, purity ≥99.5%): concentration 0.2-0.3 mol / L, pH 10.5-11.0.

[0104] The solution should be prepared using deionized water (resistivity > 18 MΩ·cm), filtered before use (using a 0.45 μm filter membrane), and stored at 4°C for no more than 7 days. For mineralization reactions, the solution must be preheated to room temperature before use.

[0105] Self-healing precursor compounds: using precursor compounds that can be activated at high temperatures, including:

[0106] Aluminum phosphate [AlPO4]: Particle size 1-5μm, purity ≥98%, thermal activation temperature 300-400℃, forms aluminum phosphate ceramic phase at high temperature;

[0107] Aluminum borate [2Al2O3·B2O3]: Particle size 2-8μm, purity ≥97%, thermal activation temperature 500-600℃, forms aluminum borosilicate ceramic phase at high temperature;

[0108] Aluminum hydroxide [Al(OH)3]: Particle size 0.5-2μm, purity ≥99%, thermal activation temperature 700-800℃, forms a mullite-like ceramic phase at high temperature.

[0109] These precursors remain inert at room temperature but are activated within a specified high-temperature range, reacting with the surrounding mineralized framework to form different types of ceramic phases that fill cracks and damage in the material. The precursors should be mixed in a 1:1:1 mass ratio, with the total amount controlled to 15-25 wt% of the total material mass. The activation performance of the precursors was confirmed by DSC-TGA analysis, and the activation products were characterized by XRD analysis.

[0110] Plant fiber materials: These utilize natural, renewable plant fibers as raw materials for subsequent processes, forming a stable carbon structure under high-temperature conditions. Specific selection:

[0111] Flax fiber: diameter 15-25μm, length 20-30mm, tensile strength approximately 800-1500MPa, containing 70-75% cellulose, 15-20% hemicellulose, and 5-10% lignin;

[0112] Bamboo fiber: 10-20μm in diameter, 2-3mm in length, tensile strength of approximately 900-1600MPa, containing 40-45% cellulose, 20-25% hemicellulose, and 25-30% lignin;

[0113] Straw fiber: 20-40μm in diameter, 1-5mm in length, tensile strength of about 400-600MPa, containing 35-45% cellulose, 25-35% hemicellulose, and 15-25% lignin.

[0114] Preferred fibers should meet the following requirements: aspect ratio > 50, cellulose content > 60%, and thermal stability (carbon residue > 30% after treatment at 400℃ for 1 hour, as determined by TGA).

[0115] Attapulgite: High-purity attapulgite (purity ≥95%, particle size 0.5-2μm, interlayer spacing 1.2-1.5nm, cation exchange capacity 80-120meq / 100g, specific surface area 150-250m² / g) was used as the target for chemical modification to alter its interlayer chemical composition and promote self-healing reactions at high temperatures. The structure and purity of the attapulgite were confirmed by XRD and FTIR characterization.

[0116] Auxiliary materials:

[0117] Anti-exudation binder: Sodium polyacrylate (molecular weight 100,000-300,000 Da), dosage 2-5 wt% of total mass;

[0118] SAP superabsorbent polymer (SAP): Sodium polyacrylate cross-linked polymer (absorption rate 300-500 times, particle size 100-300μm), dosage 3-8 wt% of total mass;

[0119] Expanded perlite: density 80-120 kg / m³, particle size 0.5-2 mm, thermal conductivity 0.04-0.06 W / (m·K), dosage 10-20 wt% of total mass;

[0120] Mineralization inducer: polyaspartic acid (molecular weight 5,000-10,000 Da) or polyglutamic acid (molecular weight 10,000-50,000 Da), at a concentration of 0.01-0.05 wt%.

[0121] Step 2: Plant Fiber Pretreatment

[0122] Alkali treatment activation: Plant fibers are immersed in a 5-10 wt% sodium hydroxide (NaOH, analytical grade, purity ≥98%) aqueous solution at a liquid-to-solid ratio of 20:1 (v / w) and maintained at 60-80℃ for 2-4 hours, ensuring uniform treatment by intermittent stirring (200 rpm, stirring for 30 seconds every 10 minutes). This step removes lignin and hemicellulose from the cellulose (removal rate should reach 60-80%, as detected by FTIR analysis of fiber composition changes) and increases the surface roughness of the fibers (surface roughness increases by 2-5 times, as observed by SEM). After treatment, the fibers are repeatedly rinsed with deionized water until the pH value reaches 7.0±0.5, and then dried in a 60℃ oven for 12 hours to constant weight.

[0123] High-temperature carbonization pretreatment: The alkali-treated fibers are placed in a tube furnace under an inert atmosphere such as nitrogen or argon (purity ≥99.99%, flow rate 100-200 mL / min), heated to 350-400℃ at a heating rate of 5℃ / min, and held for 1 hour to form a pre-carbonized structure. During carbonization, the temperature fluctuation inside the furnace should be monitored to be no more than ±5℃, and the cooling rate should be controlled at 2-3℃ / min. The pre-carbonized structure should have the following characteristics: carbon content 50-60% (determined by elemental analysis), specific surface area increased to 3-5 times that of the original fiber (determined by BET, reaching 50-100 m² / g), and micropore volume 0.1-0.2 cm³ / g. This structure can be further transformed into a stable carbon skeleton with graphitization tendency under subsequent high-temperature conditions (500-800℃).

[0124] Surface functional group grafting treatment: The pre-carbonized fibers are immersed in a grafting solution, the formulation of which is as follows:

[0125] Carboxylation treatment: Citric acid (C6H8O7, analytical grade, purity ≥99%) aqueous solution (concentration 0.5-1.0mol / L), with a small amount of sodium hypophosphite (NaH2PO2, analytical grade, 0.1-0.2mol / L) as a catalyst, react at 90-95℃ for 2-3 hours;

[0126] Hydroxylation treatment: A mixed solution of hydrogen peroxide (H2O2, 30wt%) and sodium hydroxide (0.1-0.2mol / L) is reacted at 40-50℃ for 1-2 hours;

[0127] Amination treatment: Tetraethylenepentamine (C8H) 23 N5, analytical grade, purity ≥95% aqueous solution (concentration 0.2-0.5mol / L), react at 70-80℃ for 3-4 hours.

[0128] The functional group grafting density should reach 0.5-2.0 mmol / g (determined by potentiometric titration), and the grafting uniformity should be confirmed by XPS analysis. Plant fibers treated in this step form a carbon structure rich in functional groups under high-temperature fire conditions, which combines with activated mineral products to form a reinforced composite phase (tensile strength increased by 30-50%, verified by mechanical testing).

[0129] Step 3: Attapulgite soil modification treatment

[0130] Interlayer ion exchange: Attapulgite (5g) was dispersed in 500mL of deionized water and dispersed for 30 minutes using a high-speed disperser (8000-10000rpm) to form a homogeneous suspension. Subsequently, a metal ion solution was added.

[0131] Aluminum ion solution: Al2(SO4)3·18H2O (analytical grade, purity ≥99%), concentration 0.1mol / L, added amount is 10-15wt% of the mass of attapulgite (calculated as metal ions).

[0132] Magnesium ion solution: MgCl2·6H2O (analytical grade, purity ≥98%), concentration 0.1mol / L, added at 5-10wt% of the mass of attapulgite soil (calculated as metal ions).

[0133] The mixed solution was stirred at 60-70℃ using a mechanical stirrer (200-300 rpm) for 6-8 hours to allow metal ions to enter the interlayer of attapulgite through ion exchange. The ion exchange efficiency was confirmed by XRD measurement of the interlayer spacing change (which should increase by 0.2-0.4 nm) and ICP-AES measurement of the ion concentration change in the solution (the exchange rate should reach above 80%). After completion, the solid was collected by centrifugation (5000 rpm, 10 minutes) and washed 3-5 times with deionized water until the conductivity of the filtrate was <100 μS / cm. The filtrate was then dried at 60℃ for 12 hours.

[0134] Organic modification: 3g of ion-exchanged attapulgite was dispersed in 100mL of 95% ethanol and sonicated for 30 minutes, followed by the addition of an organic modifier.

[0135] Quaternary ammonium salt modifier: Octadecyltrimethylammonium chloride (CTAC, C 21 H 46 ClN (analytical grade, purity ≥98%), used at a rate of 30-40 wt% of the attapulgite mass, or

[0136] Organosilane coupling agent: 3-aminopropyltriethoxysilane (APTES, C9H) 23 NO3Si (analytical grade, purity ≥98%), the dosage is 15-25 wt% of the attapulgite mass.

[0137] The mixture was stirred at 80℃ for 4-6 hours (pH should be controlled at 6-7, adjusted with dilute hydrochloric acid or sodium hydroxide solution if necessary) to allow the organic modifier to intercalate into the attapulgite layers. Successful grafting of the organic component was confirmed by FTIR (characteristic peaks located at 2800-3000 cm⁻¹). -1 The organic component content was determined by TGA (should be 10-20 wt%). After modification, the sample was collected by centrifugation, washed three times alternately with ethanol and deionized water, and then vacuum dried at 60°C for 12 hours.

[0138] Heat treatment activation: The organically modified attapulgite is placed in a muffle furnace and heated to 200-250℃ at a rate of 2℃ / min, held at that temperature for 2 hours, and then heat-treated in air. Through heat treatment, the organic modifier partially degrades to form active sites with a special chemical composition, changing the interlayer structure of the attapulgite (XRD measurement shows a reduction in interlayer spacing of 0.1-0.2 nm), enabling it to promote the activation reaction of self-healing precursors at high temperatures. The heat-treated attapulgite should have UL-94 V-0 flame retardant performance (self-extinguishing time <10 seconds in vertical burning test) and should be able to catalyze a 20-30% increase in the conversion rate of self-healing precursors at high temperatures (test conditions: 500℃, 2 hours) (measured by XRD changes in crystal phase content).

[0139] Step 4: Construction of the biomineralized inorganic framework

[0140] Preparation of mineralization solution: Sodium silicate solution (0.2-0.3 mol / L) and calcium chloride solution (0.24-0.36 mol / L) are mixed at a molar ratio of 1:1.2. A mineralization inducer (such as polyaspartic acid, polyglutamic acid, etc., at a concentration of 0.01-0.05 wt%) is added, and the pH is adjusted to 8.0-8.5 to obtain the biomineralization reaction solution. This ratio maintains a suitable supersaturation state of silicate and calcium ions in the solution, which is conducive to directional deposition on the solid surface.

[0141] Multi-stage mineralization process:

[0142] First-stage mineralization: Pretreated plant fibers (15-20 wt% of total material mass) and a portion of phase change material (10-15 wt% of total material mass) are immersed in a mineralization solution (solid-liquid ratio 1:10 w / v) and slowly stirred (80-100 rpm) in a constant temperature water bath at 30-40℃ for 12-24 hours. During this stage, calcium silicate (mainly CSH gel and microcrystalline calcium silicate) is deposited on the fiber surface, with a deposition thickness of 1-3 μm (measured by SEM), a deposition amount of 20-30 wt% of the fiber mass (determined by TGA), and a crystallinity of 30-40% for the mineralization product (determined by XRD).

[0143] Second-stage mineralization: A sodium carbonate solution (0.2 mol / L, 20% of the volume of the solution from the first stage) is added to the system, and the reaction continues at 35-45℃ for 6-8 hours to form a composite mineralization layer of calcium carbonate (mainly aragonite and calcite, with a particle size of 0.5-2 μm), increasing the thickness to 3-5 μm. The compressive strength of the composite mineralization layer formed in this stage should reach 5-8 MPa (through nanoindentation testing), and the porosity should be 40-50% (through BET and pore size distribution analysis).

[0144] Third-stage mineralization: A mixture of self-healing precursor compounds (total amount 15-20 wt% of the already mineralized material) is added, and the mixture is further reacted at 40-50℃ for 8-12 hours to ensure that the precursors are uniformly distributed in the mineralized framework, forming self-healing sites. Energy dispersive spectroscopy (EDS) analysis confirms the uniform distribution of precursor elements (Al, P, B, etc.) in the mineralized framework (elemental distribution coefficient of variation CV < 10%).

[0145] Precise control of mineralization process parameters: The formation of an inorganic framework with a continuous network structure is controlled by the following parameters:

[0146] Solution concentration control: Use an online conductivity monitor to monitor changes in ion concentration (conductivity should be maintained within the range of 8-12 mS / cm), and add supplementary solution as needed to adjust;

[0147] pH control: Use an automatic pH controller to maintain the pH within the range of 8.0-8.5 (fluctuation not exceeding ±0.2), and adjust with 0.1mol / L NaOH or HCl if necessary;

[0148] Temperature control: A constant temperature device is used to control the reaction temperature (fluctuation not exceeding ±1℃) to ensure the stable progress of the mineralization process;

[0149] Reaction time control: The reaction endpoint is determined by sampling and analyzing the degree of mineralization (sampling once every 4 hours, and monitoring the intensity changes of characteristic peaks of Si-O-Si and Ca-O bonds by FTIR).

[0150] During the mineralization process, the layered structure of modified attapulgite provides additional mineralization sites (50-100 m² of effective surface area per gram of attapulgite), promotes the deposition of inorganic matter, and enhances the connectivity and integrity of the skeletal network (the network connectivity should reach over 85% through micro-CT three-dimensional reconstruction analysis).

[0151] Framework stabilization treatment: The mineralized material is collected by vacuum filtration and dried in a circulating oven at 90-100℃ for 8-12 hours (drying is considered complete when the weight change is <0.5% / h). It is then transferred to a tube furnace and heated to 200-250℃ at a rate of 1-2℃ / min under a nitrogen atmosphere (flow rate 100-200ml / min), and held for 2 hours to achieve dehydration stabilization and crystallization of the inorganic framework, while keeping the self-healing precursor in an inert state (DSC confirms the precursor is not activated; activation characteristic peaks should be above 300℃).

[0152] Through the aforementioned precisely controlled biomineralization process, a continuous inorganic framework network with a hierarchical pore structure is formed in the material (pore size distribution: micropores <2nm account for 20%, mesopores 2-50nm account for 50%, and macropores >50nm account for 30%). This framework possesses a high specific surface area (80-120m² / g) and good mechanical strength (compressive strength 8-12MPa). Under high-temperature conditions (>500℃), the framework transforms into a ceramic phase with higher stability (mainly calcium silicate, calcium aluminum silicate, etc.), effectively restricting the flow of the phase change material in the molten state (liquid leakage rate <5%), while providing an ideal reaction carrier and material transport channel for the high-temperature activated self-healing system.

[0153] Step 5: Composite of multilayer gradient phase change materials

[0154] Gradient layered structure: Based on fireproof and heat insulation requirements, phase change materials with different melting points are layered in order of gradually increasing melting point from the outside to the inside. The outer layer uses low melting point materials (60-120℃), the middle layer uses medium melting point materials (200-350℃), and the inner layer uses high melting point materials (350-450℃).

[0155] Microencapsulation of phase change materials:

[0156] Microencapsulation of organic phase change materials: Paraffin-based organic phase change materials are encapsulated within a heat-resistant polymer shell using interfacial polymerization. Specific steps are as follows:

[0157] Preparation of the oil phase: Dissolve paraffin (melting point 50-60℃, 150g) in cyclohexane (200mL) and add triisocyanate (15g) as a monomer;

[0158] Preparation of the aqueous phase: Polyvinyl alcohol (molecular weight approximately 88,000, 300 mL of 1 wt% aqueous solution) was mixed with diethylenetriamine (10 g), and the pH was adjusted to 9.5-10.0;

[0159] Emulsification: The oil phase is slowly added dropwise to the aqueous phase at a speed of 5000 rpm to form an O / W type emulsion, and emulsification is carried out for 30 minutes;

[0160] Polymerization reaction: React at 40-45℃ for 3 hours to form a polyurethane shell;

[0161] Post-processing: Collect microcapsules by centrifugation, wash three times with deionized water, and freeze-dry for 24 hours.

[0162] The final microcapsules had a diameter of 5-20 μm (measured by laser particle size analyzer, particle size distribution CV <15%), a wall thickness of 0.5-1.0 μm (measured by TEM), an encapsulation rate of >95% (determined by DSC), and a temperature resistance of >300℃ (TGA test, 5% mass loss temperature).

[0163] Inorganic hydrated salt immobilization: Sodium sulfate decahydrate was immobilized by coating with modified SAP superabsorbent polymer (absorption ratio 300-500 times). The specific steps are as follows:

[0164] The SAP resin (20g) was preheated at 50°C for 1 hour to activate it;

[0165] Slowly add sodium sulfate aqueous solution (concentration 40-50wt%, 100mL) dropwise to SAP, controlling the liquid-to-solid ratio at 4-5:1;

[0166] Let the mixture stand at room temperature for 4-6 hours to allow the SAP to fully absorb the salt solution;

[0167] Dry at 60℃ until the moisture content is 20-25% (determined by weight loss analysis);

[0168] The dried material is mixed with a crosslinking agent (epoxy resin, 3-5 wt%) to form a stable structure.

[0169] After 100 thermal cycles (0-100℃), the inorganic hydrated salt fixative exhibits a salt loss rate of <3% (determined by mass analysis) and a latent heat retention rate of >90% (determined by DSC).

[0170] Multilayer composite process (layered construction):

[0171] Outer layer structure construction: Low-melting-point microencapsulated phase change material (20-25 wt% of total material mass) and a portion of the mineralized framework (15-20 wt% of total material mass) are mixed in a V-type mixer (30 rpm, 30 minutes). Then, a 5 wt% aqueous solution of polyvinyl alcohol binder (10% of the dry material mass) is added and mixed thoroughly. The mixture is then pre-pressed at room temperature (5-8 MPa, held for 5 minutes). The outer layer thickness is controlled at 8-12 mm, the density at 300-350 kg / m³, and the thermal conductivity at 0.08-0.10 W / (m·K).

[0172] Intermediate layer construction: A medium-melting-point phase change material (15-20 wt% of total material mass) is mixed with a mineralized framework (10-15 wt%) and partially modified attapulgite (5-8 wt%), along with a silicate-based inorganic binder (8-10 wt%). The mixture is then mixed in a rotary mixer (40 rpm, 20 minutes). This mixture is then spread onto a pre-formed outer layer and molded under pressure of 10-12 MPa for 10 minutes. The intermediate layer thickness is controlled at 12-15 mm, with a density of 400-450 kg / m³ and a thermal conductivity of 0.07-0.09 W / (m·K).

[0173] Inner layer construction: High-melting-point phase change material (10-15 wt%) is mixed with a mineralized skeleton (10-15 wt%), pretreated plant fibers (8-10 wt%), and the remaining modified attapulgite (5-8 wt%). Aluminosilicate binder (10-12 wt%) is added, and the mixture is stirred in a planetary mixer (50 rpm, 15 minutes). The mixture is then laid on the intermediate layer, molded under pressure of 15-20 MPa, and held for 15 minutes. The inner layer thickness is controlled at 15-20 mm, the density is 450-550 kg / m³, and the thermal conductivity is 0.06-0.08 W / (m·K).

[0174] Interlayer bonding treatment: A mineralized framework extension bonding technology is used to lay a transition layer (1-2 mm thick) composed of nano-calcium silicate fibers (50-200 nm in diameter and 5-10 μm in length) between layers to enhance interlayer bonding strength. The integrity of interlayer bonding is confirmed by micro-CT scanning, and the interlayer shear strength should reach 0.5-0.8 MPa (verified by interlayer shear test).

[0175] Enhanced Interface Integration: A dedicated interface bonding agent is added between each layer, specifically:

[0176] Outer and intermediate layer interface: Aluminosilicate sol (SiO2 / Al2O3 molar ratio = 3:1, solid content 15-20wt%) is used, with a coating amount of 100-150g / m².

[0177] Intermediate layer and inner layer interface: Use modified silane coupling agent (γ-aminopropyltriethoxysilane, 5wt% ethanol solution), with a coating amount of 80-120 g / m².

[0178] After coating, heat-treat at 60-70℃ for 2-3 hours to cure the interfacial adhesive. The interfacial bond strength is determined by an interlayer peel test, and the peel strength should be ≥1.0 N / mm (tested according to ASTM D3330 standard). After 10 temperature cycles from -20℃ to 150℃, the interfacial bond strength retention rate should be ≥85%.

[0179] Through this step, the material forms a gradient multilayer phase change heat storage structure. When exposed to high temperatures, the outer layer of phase change material first absorbs heat and undergoes a phase change (with an endothermic value of approximately 200-300 J / g). Subsequently, the middle and inner layers of phase change material absorb heat in sequence, forming an ordered thermal resistance hierarchy that gradually slows down the rate of heat transfer, achieving a fireproof and heat-insulating effect. When the outer layer temperature reaches 60-120℃, only the outer layer of phase change material undergoes a phase change, while the internal temperature remains stable. When the temperature continues to rise to 200-350℃, the middle layer begins to undergo a phase change and absorb heat. Only when the temperature reaches above 350℃ does the inner layer of phase change material begin to function, thus achieving long-term heat insulation.

[0180] Step Six: Construction of the High-Temperature Activation Self-Healing System

[0181] Self-healing precursor composite design:

[0182] Precursor formulation: The self-healing precursor compounds dispersed in the mineralized framework in step four are compounded according to the following formulation:

[0183] Low-temperature activated precursor: aluminum phosphate [AlPO4], particle size 1-5 μm, accounting for 30-35 wt% of the total precursor;

[0184] Medium-temperature activated precursor: aluminum borate [2Al2O3·B2O3], particle size 2-8 μm, accounting for 30-35 wt% of the total precursor;

[0185] High-temperature activated precursor: aluminum hydroxide [Al(OH)3], with a particle size of 0.5-2μm, accounting for 30-35wt% of the total precursor.

[0186] Addition of activation accelerator: Mix the transition metal oxide activation accelerator with the precursor at a mass ratio of 3:1.

[0187] Copper oxide [CuO]: purity ≥99%, particle size <1μm, accounting for 40-45wt% of the total accelerator;

[0188] Manganese oxide [MnO2]: purity ≥98%, particle size <1μm, accounting for 30-35wt% of the total accelerator;

[0189] Cobalt oxide [Co3O4]: purity ≥98%, particle size <1μm, accounting for 20-25wt% of the total accelerator.

[0190] Adding a sustained-release system: Introducing the following phosphorus- and silicon-containing sustained-release compounds to form a temperature gradient-responsive activation system:

[0191] Ammonium pyrophosphate [(NH4)4P2O7]: purity ≥98%, addition amount is 5-8 wt% of the total precursor;

[0192] Aluminum silicate [Al2SiO5]: purity ≥99%, particle size 1-3μm, addition amount is 8-10wt% of the total precursor.

[0193] The precursor complex was dry-mixed for 30 minutes using a high-speed mixer (8000-10000 rpm) to ensure homogeneity (confirmed by SEM-EDS elemental distribution analysis, with an elemental distribution variation coefficient CV < 5%).

[0194] Construction of 3D activation network:

[0195] Basic network construction: The self-healing precursor complex (15-20 wt% of the total material mass) and the modified attapulgite (8-10 wt% of the total material mass) are mixed and dispersed under ultrasonic assistance (power 300-500W, frequency 20-25kHz, treatment time 10-15 minutes) so that the precursor part enters the interlayer of attapulgite (intercalation rate should reach 40-50%, as determined by XRD).

[0196] Fiber-reinforced network construction: Pretreated plant fibers (5-8 wt% of total material mass) are added, and mechanical stirring (200-300 rpm) and ultrasonic alternating treatment (5 minutes of mechanical stirring, 2 minutes of ultrasonic treatment, 3 cycles) are used to form a three-dimensional interconnected activated network.

[0197] Activated network stabilization: Add inorganic cementitious material (water glass, modulus 2.0-2.5, 3-5 wt% of total mass) as a network stabilizer, and dry at 60-70℃ for 2-3 hours. The formed activated network should have the following characteristics: porosity 40-50% (determined by mercury porosimetry), specific surface area 80-100 m² / g (determined by BET), and compressive strength 3-5 MPa.

[0198] Precise control through multiple activation mechanisms:

[0199] Temperature-gradient activation mechanism: Activation temperature ranges of different precursors were verified by DSC-TGA analysis.

[0200] Low-temperature activated components: activation temperature 300-400℃, activation enthalpy 150-180J / g, activation degree >90%;

[0201] Medium-temperature activated components: activation temperature 500-600℃, activation enthalpy 180-220J / g, activation degree >85%;

[0202] High-temperature activated component: activation temperature 700-800℃, activation enthalpy 220-250J / g, activation degree >80%.

[0203] Synergistic catalytic activation mechanism: Achieving synergistic catalysis between plant fiber carbonization products and attapulgite.

[0204] Plant fibers are carbonized at 400-500℃ to form a catalytically active carbon structure (graphitization degree 15-25%, specific surface area 300-500m² / g).

[0205] Modified attapulgite releases active oxygen substances at high temperatures, reducing the activation energy of the precursor;

[0206] The synergistic effect of the two factors reduces the precursor activation temperature by 20-30℃ and increases the reaction rate by 30-50% (determined by isothermal kinetic analysis).

[0207] Structure control of activation products: The composition of activation products was confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The main components are aluminosilicate (mullite, cordierite, etc.), aluminophosphate and borosilicate ceramic phases, with a crystallinity of 60-70%.

[0208] Precise formulation for self-healing reaction:

[0209] Precursor-skeleton ratio optimization: The mass ratio of self-healing precursor to mineralized skeleton is controlled within the range of 1:2-1:3. This ratio has been verified by thermogravimetric analysis and mercury intrusion porosimetry, which can ensure that the ceramic phase filling rate reaches 85-95%.

[0210] Performance control of repair products: The ceramic phase formed at high temperature has the following characteristics:

[0211] Compressive strength: 8-12MPa (through nanoindentation test);

[0212] Apparent porosity: 5-10% (determined by mercury porosimetry);

[0213] Thermal conductivity: 0.3-0.5 W / (m·K) (measured by laser scintillation method);

[0214] Hardness: 5-7 Mohs hardness (measured by a microhardness tester).

[0215] Repair kinetic control: Optimal repair kinetic parameters were determined using differential scanning calorimetry (DSC) and thermal expansion analysis (TMA).

[0216] Optimal repair temperature range: 550-650℃;

[0217] Optimal repair time: 30-60 minutes;

[0218] Activation energy of the repair reaction: 120-150 kJ / mol.

[0219] Through this core innovative step, this implementation method achieves the automatic repair function of the material structure after experiencing a high-temperature fire. The specific repair mechanism is as follows: when the material is subjected to high temperatures (above 300°C), causing surface cracks or localized damage, the self-repairing precursor is activated by the high temperature, reacting with the surrounding mineralized skeleton and plant fiber carbonization products to generate a ceramic phase, filling the cracks and rebuilding structural integrity. The repair process continues during the material's cooling phase after the fire. The formed ceramic phase has high strength and low thermal conductivity, restoring 70-80% of the material's thermal insulation function. This repair mechanism requires no additional operation, relying entirely on the heat energy provided by the fire itself to achieve automatic repair, overcoming the limitation of traditional fireproof materials being used only once.

[0220] Step 7: Molding and Curing

[0221] Material forming process:

[0222] Mold preparation: Use a stainless steel mold (material 304 stainless steel, inner cavity surface roughness Ra≤0.8μm), and use silicone oil (viscosity 500-1000cSt) as a release agent, and apply it evenly to the inner surface of the mold (coating amount 50-100mg / m²).

[0223] Pressure molding: The composite material prepared in step six (moisture content controlled at 8-12%, measured by an infrared moisture analyzer) is loaded into the mold, and the hydraulic molding process is performed according to the following parameters:

[0224] Pre-compression: Pressure 5-8 MPa, maintain for 2 minutes to expel most of the air;

[0225] Main pressure: The pressure is gradually increased to 15-20 MPa, with a pressurization rate of 1-2 MPa / s;

[0226] Pressure holding: Maintain at the final pressure of 15-20 MPa for 8-10 minutes;

[0227] Depressurization: Depressurize slowly in 3-5 stages, with a 30-second interval between each stage, to prevent material rebound.

[0228] Demolding: After molding, allow the material to cool to room temperature (cooling rate approximately 1-2℃ / min), then demold using a pneumatic ejection device (air pressure 0.6-0.8MPa) to avoid mechanical damage. The density of the molding material should be in the range of 500-650kg / m³ (determined by Archimedes' displacement method), and the compressive strength should be ≥5MPa (tested according to ASTM C165 standard).

[0229] Layered composite molding (optional): For fireproof and heat-insulating materials that require layering, the following layered molding process is adopted:

[0230] Inner layer placement: First, place the inner layer material (350-450℃ phase change material composite system) at the bottom of the mold, and initially compact it with low pressure (8-10MPa) for 1-2 minutes;

[0231] Middle layer addition: The middle layer material (200-350℃ phase change material composite system) is evenly laid on the inner layer material, with an edge overlap width of ≥10mm to ensure interlayer bonding;

[0232] Outer layer completion: Finally, lay out the outer layer material (60-120℃ phase change material composite system) to ensure a smooth surface;

[0233] Overall pressing: A multi-stage pressure control process is adopted, with an initial pressure of 10MPa, gradually increasing to 20MPa, and a total holding time of 15-20 minutes;

[0234] Interlayer bonding test: The quality of interlayer bonding is tested by ultrasonic C-scan. The bonding area should be ≥95% and the interlayer peel strength should be ≥0.8MPa (tested according to ASTM D1781 standard).

[0235] Precision curing process:

[0236] Preliminary drying: The shaped material is placed in a precision temperature-controlled oven and dried in stages under humidity-controlled conditions (relative humidity 30-40%).

[0237] Dry at 40-50℃ for 4-6 hours;

[0238] Dry at 60-70℃ for 6-8 hours;

[0239] Dry at 80-120℃ for 12-24 hours until the weight change rate is <0.1% / h.

[0240] Heat treatment curing: The dried material is transferred to a programmable heat treatment furnace and cured using the following temperature profile:

[0241] The temperature was increased to 150°C at a rate of 2°C / min and held for 2 hours.

[0242] Heat to 180-200℃ at a rate of 1℃ / min and hold for 4-6 hours;

[0243] Allow to cool naturally to room temperature (cooling rate <3℃ / min).

[0244] The cured material should meet the following requirements: dry density 500-600 kg / m³, linear shrinkage rate <1%, surface hardness ≥70 (ShoreD hardness tester, tested according to ASTM D2240 standard), and water resistance meeting the Class 2 requirements of GB / T 9775 (24h water absorption rate <5%).

[0245] Functional surface treatment (optional): The following surface treatment processes are adopted according to the application requirements:

[0246] Waterproofing treatment: Use silicone waterproofing agent (silicone content ≥28%), spraying amount 150-200g / m², cure at 60℃ for 2 hours, the waterproofing level reaches Class II (water absorption rate <2%) in GB 50108-2008.

[0247] Wear-resistant treatment: Alumina-epoxy composite coating is used (alumina particle size 60-80μm, accounting for 30-40% of the coating mass), coating thickness 0.3-0.5mm, hardness ≥7H (pencil hardness, tested according to ISO 15184 standard), wear resistance ≥100mg (Taber wear, CS-17 grinding wheel, 1000 rpm, 1kg load);

[0248] Decorative treatment: As needed, acrylic or silicate coatings containing flame retardants (flame retardant rating reaching B1 level in GB8624-2012) can be used, with a coating thickness of 0.2-0.3mm and an adhesion of ≥2MPa (pull-out method, tested according to ISO 4624 standard).

[0249] Step 8: Performance Testing and Quality Control

[0250] This step includes the following key performance tests:

[0251] Thermal performance testing:

[0252] Thermal conductivity determination: The heat flow meter method (according to GB / T 10294-2008) is used. The test temperature range is 25-800℃, and the test result should be 0.06-0.08W / (m·K)@25℃.

[0253] Specific heat capacity determination: Differential scanning calorimetry (DSC, according to ASTM E1269-11) is used, with a test temperature range of 25-500℃, and the specific heat capacity should be 1.2-1.6 kJ / (kg·K)@25℃;

[0254] Thermal resistance determination: The hot box method (according to GB / T 13475-2008) is adopted. The sample size is 300mm×300mm, the thickness is as actual, and the thermal resistance value should be ≥2.0m²·K / W (under the condition of 50mm thickness).

[0255] Fire resistance performance test:

[0256] Non-combustibility test: conducted according to GB / T 5464-2010, the material should meet the Class A non-combustibility requirement;

[0257] Fire resistance limit test: conducted according to GB / T 9978.1-2008, the fireproof and heat insulation time should be ≥180 minutes (more than 50% longer than traditional materials);

[0258] Surface combustion characteristics: According to ASTM E84, flame spread index ≤25, smoke development index ≤50.

[0259] Mechanical performance testing:

[0260] Compressive strength: According to GB / T 5486-2008, it should be ≥8MPa;

[0261] Bending strength: According to GB / T 5487-2008, it should be ≥3MPa;

[0262] Impact toughness: According to GB / T 1043.1-2008, it should be ≥15kJ / m².

[0263] Self-healing effect evaluation:

[0264] Repair efficiency test: Pre-cracks (width 0.5-1.0mm, depth 5-10mm) are created on the material surface, and then heat-treated at 500-600℃ for 1 hour. The crack filling rate should be ≥90% (analyzed by micro-CT tomography).

[0265] Performance recovery rate test after repair: Compare the thermal conductivity, compressive strength and other performance parameters before and after repair. The recovery rate should reach 70-80% (e.g., the thermal conductivity after repair should not exceed 1.2 times that before repair).

[0266] Cyclic repair capability test: Perform 3-5 "damage-repair" cycles to assess the repeatability of the material's self-repair capability. The reduction in repair efficiency should be less than 15% per cycle.

[0267] All test results must comply with relevant national or industry standards, and a complete test report must be generated as the basis for product quality control. Test samples should be randomly selected from different batches of products to ensure the representativeness of the test results.

[0268] Experimental verification

[0269] To verify the technical effects of the present invention, we conducted the following experimental tests.

[0270] Experiment 1: Verification of High-Temperature Activation Self-Healing Function

[0271] Experimental Objective

[0272] The self-repairing ability of the material of the present invention after being subjected to high temperature damage, and the degree of performance recovery after repair, were verified.

[0273] Experimental Design

[0274] The self-repair ability and thermal insulation performance recovery of the material of this invention (sample A) were compared with those of three traditional fireproof and heat-insulating materials (sample B: organic fireproof insulation board, sample C: inorganic fireproof insulation board, sample D: ceramic fiber insulation material) under the same high-temperature damage conditions.

[0275] Experimental steps

[0276] Sample preparation:

[0277] Sample A: The material of the present invention was prepared according to Embodiment 1, with dimensions of 100mm × 100mm × 25mm;

[0278] Sample B: Commercially available organic fireproof insulation board, dimensions 100mm×100mm×25mm;

[0279] Sample C: Commercially available inorganic fireproof insulation board, dimensions 100mm×100mm×25mm;

[0280] Sample D: Commercially available ceramic fiber insulation material, dimensions 100mm×100mm×25mm.

[0281] Initial test:

[0282] The initial thermal conductivity of each sample was determined using the heat flow meter method (GB / T 10294-2008);

[0283] The initial compressive strength of each sample was determined using a pressure testing machine (GB / T 5486-2008).

[0284] Artificial damage creation:

[0285] Standard cracks (width 1.0±0.1mm, depth 8.0±0.5mm) were created on the surface of each sample along the diagonal direction.

[0286] The initial state of the crack was recorded using a high-precision digital microscope.

[0287] High-temperature treatment to simulate fire:

[0288] Place all samples into a high-temperature muffle furnace;

[0289] The temperature was increased to 550±10℃ at a rate of 10℃ / min;

[0290] Maintain a constant temperature of 550℃ for 60 minutes;

[0291] Allow it to cool naturally to room temperature (approximately 5-6 hours).

[0292] Repair effectiveness assessment:

[0293] Three-dimensional tomographic scanning of each sample was performed using micro-CT to calculate the crack filling rate.

[0294] The thermal conductivity and compressive strength of each sample were measured again.

[0295] Calculate the performance recovery rate (performance after repair / initial performance).

[0296] Experimental results

[0297] Table 1. Crack filling rate and performance recovery of each sample

[0298]

[0299] Figure 1 The comparison of the crack state of sample A before and after repair is shown;

[0300] Figure 2 The comparison of the crack state of sample B before and after repair is shown;

[0301] Figure 3 The comparison of the crack state of sample C before and after repair is shown;

[0302] Figure 4 The comparison of the crack state before and after the repair of sample D is shown.

[0303] Figure 5 The comparison of the performance recovery rates of each sample is shown.

[0304] Experimental Conclusion: The material of this invention exhibits excellent self-healing ability after high-temperature treatment, with a crack filling rate of 92.5%, far exceeding that of the comparative sample. After repair, the thermal conductivity and compressive strength recovery rates of the material of this invention reached 78.6% and 76.3%, respectively. This means that it can retain most of its original performance after experiencing a high-temperature fire and can continue to be used without replacement. In contrast, traditional fireproof and heat-insulating materials have almost no self-healing ability, with performance recovery rates generally below 45%, requiring replacement after a fire in practical applications. This fully verifies the effectiveness and innovation of the high-temperature activated self-healing system of this invention.

[0305] Experiment 2: Verification of the thermal insulation performance of multi-layer gradient phase change thermal storage

[0306] Experimental Objective

[0307] The thermal insulation performance of the multilayer gradient phase change thermal storage structure of the present invention under different temperature conditions was verified, as well as its advantages over traditional single-layer phase change materials.

[0308] Experimental Design

[0309] The thermal insulation effect of the multilayer gradient structure material (sample E) of the present invention was compared with three single-layer structure materials: a single-layer material containing only low-melting-point phase change material (sample F), a single-layer material containing only medium-melting-point phase change material (sample G), and a single-layer material containing only high-melting-point phase change material (sample H) under different temperature gradients.

[0310] Experimental steps

[0311] Sample preparation:

[0312] Sample E: A multilayer gradient structure sample was prepared according to Embodiment 1, with dimensions of 100mm×100mm×50mm. From the outside to the inside, it consists of a low melting point layer (60-120℃, 10mm thick), a medium melting point layer (200-350℃, 15mm thick), and a high melting point layer (350-450℃, 25mm thick).

[0313] Sample F: A homogeneous material containing only low-melting-point phase change material (60-120℃), with dimensions of 100mm×100mm×50mm;

[0314] Sample G: A homogeneous material containing only medium-melting-point phase change material (200-350℃), with dimensions of 100mm×100mm×50mm;

[0315] Sample H: A homogeneous material containing only high-melting-point phase change material (350-450℃), with dimensions of 100mm×100mm×50mm.

[0316] Experimental setup:

[0317] The hot chamber method testing device conforms to GB / T 13475-2008 standard;

[0318] One side of the hot box is a high-temperature zone with an adjustable temperature range of 20-900℃;

[0319] The other side of the hot box is the room temperature zone, maintained at 25±2℃;

[0320] The sample was installed between the two zones and sealed and secured with heat-insulating material around it.

[0321] Thermocouples were installed on both sides of the sample and at the interfaces of each internal layer, and connected to the data acquisition system.

[0322] Temperature gradient test:

[0323] Test 1: Set the temperature of the high-temperature zone of the hot box to 100℃, observe continuously for 2 hours, and record the temperature changes at each measuring point;

[0324] Test 2: Set the temperature of the high-temperature zone of the hot box to 300℃, observe continuously for 2 hours, and record the temperature changes at each measuring point;

[0325] Test 3: Set the temperature of the high-temperature zone of the hot box to 600℃, observe continuously for 2 hours, and record the temperature changes at each measuring point;

[0326] Each test is conducted 24 hours apart to ensure the sample has completely cooled and returned to its initial state.

[0327] Data processing:

[0328] Calculate the temperature transfer rate (inner surface temperature rise / outer surface temperature rise) of each sample under different temperature conditions.

[0329] Calculate the effective thermal resistance of each sample at different external temperatures;

[0330] Analyze the internal temperature gradient distribution of each sample.

[0331] Experimental results

[0332] Table 2. Inner surface temperature (after 2 hours) and temperature transfer rate of each sample at different temperatures.

[0333]

[0334] Figure 6 The internal temperature distribution curves of different samples at an external surface temperature of 600℃ are shown.

[0335] Figure 7 The temperature transfer rate of each sample at different temperatures is compared.

[0336] Experimental Conclusions: Experimental results show that the multilayer gradient phase change thermal storage structure of this invention exhibits excellent thermal insulation performance under various temperature conditions. At external surface temperatures of 100℃, 300℃, and 600℃, the temperature transfer rates of the material of this invention are only 4.7%, 7.4%, and 13.8%, respectively, significantly lower than those of single-layer materials. Particularly under high-temperature conditions (600℃), the internal surface temperature of the material of this invention is only 104.6℃, far lower than other single-layer materials (the lowest reaching 216.7℃). This indicates that the multilayer gradient structure of this invention can exert a synergistic effect in different temperature ranges. As the temperature increases, each layer of phase change material sequentially exerts its thermal insulation function, forming a continuous thermal resistance hierarchy that effectively prevents heat transfer inward. This gradient thermal insulation effect is unattainable by traditional single-layer materials, fully demonstrating the innovation and effectiveness of the multilayer gradient phase change thermal storage structure of this invention.

[0337] Experiment 3: Verification of the Influence of Biomineralized Framework on the Stability of Phase Change Materials

[0338] Experimental Objective

[0339] The purpose of this invention is to verify the effect of the biomineralized inorganic framework on the fixation of phase change materials and to evaluate the stability and performance retention of phase change materials under multiple thermal cycling conditions.

[0340] Experimental Design

[0341] The material of this invention (sample I) with a biomineralized inorganic framework was compared with three traditional phase change material immobilization methods: microencapsulation (sample J), ​​porous material impregnation (sample K), and direct mixing (sample L). The loss rate and performance changes of the phase change material were tested after multiple thermal cycles.

[0342] Experimental steps

[0343] Sample preparation:

[0344] Sample I: A phase change material containing a biomineralized inorganic framework was prepared according to Embodiment 1, with dimensions of 50mm × 50mm × 10mm;

[0345] Sample J: Phase change material was microencapsulated using interfacial polymerization, with dimensions of 50mm × 50mm × 10mm;

[0346] Sample K: Made of porous calcium silicate impregnated with phase change material, with dimensions of 50mm×50mm×10mm;

[0347] Sample L: The phase change material and the binder were directly mixed, with dimensions of 50mm × 50mm × 10mm;

[0348] The initial content of phase change material in all samples was controlled at 40±2wt%.

[0349] Initial performance testing:

[0350] The initial latent heat of phase change for each sample was determined using differential scanning calorimetry (DSC).

[0351] The initial thermal conductivity of each sample was determined using a thermal conductivity meter.

[0352] Measure and record the initial mass of each sample.

[0353] Thermal cycling test:

[0354] Place the sample in a programmable thermal cycling test chamber;

[0355] Heating phase: Increase temperature from room temperature to 120°C and maintain for 1 hour;

[0356] Cooling phase: Cool from 120℃ to 25℃ and hold for 1 hour;

[0357] Repeat the above cycle 100 times;

[0358] After every 10 cycles, the sample is removed and the mass change and phase transition properties are measured.

[0359] Phase change material leakage test:

[0360] Place the sample in a constant temperature environment of 90℃;

[0361] Place absorbent paper at the bottom and weigh the change in the mass of the absorbent paper at regular intervals;

[0362] The test lasted 48 hours, with data recorded every 4 hours.

[0363] Data processing:

[0364] Calculate the phase change material loss rate (mass loss / initial phase change material mass) of each sample after thermal cycling.

[0365] Calculate the latent heat retention rate of phase change (latent heat value after cycle / initial latent heat value).

[0366] Experimental results

[0367] Table 3. Comparison of the stability of phase change materials of each sample after 100 thermal cycles

[0368]

[0369] Figure 8 The changes in the cumulative loss rate of phase change material for each sample during thermal cycling are shown.

[0370] Experimental Conclusions: The experimental results demonstrate that the method of immobilizing phase change materials using a biomineralized inorganic framework, as described in this invention, has significant advantages. After 100 thermal cycles, the phase change material loss rate of the material from this invention was only 3.2%, significantly lower than the other three traditional immobilization methods (microencapsulation 8.7%, porous material impregnation 15.6%, and direct mixing 32.5%). Furthermore, the material from this invention retained 95.8% of its initial latent heat of phase change, indicating that its phase change performance is almost unaffected by thermal cycling.

[0371] In long-term leakage tests under constant temperature conditions of 90℃, the cumulative leakage of the material of this invention after 48 hours was only 0.26 mg / cm², which is only 3.2% of that of the direct mixing method, 22.4% of that of the microencapsulation method, and 8.5% of that of the porous impregnation method. These data fully demonstrate that the biomineralized inorganic framework can effectively encapsulate and fix the phase change material by forming a continuous network structure, preventing it from being lost in the molten state.

[0372] The advantages of biomineralized inorganic frameworks are: (1) they form a continuous three-dimensional network structure, rather than dispersed particles or point-like fixation; (2) the framework itself transforms into a stable ceramic phase at high temperatures, improving the overall structural stability; and (3) the framework and phase change material are fixed more persistently through chemical bonding. This innovative fixation method solves the most critical problem faced by traditional phase change materials in application—loss after melting—and provides reliable technical support for the application of phase change materials in the field of high-temperature fireproofing and heat insulation.

[0373] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A thermal insulation material having fireproof and heat insulating properties, characterized by comprising: a porous material having a plurality of pores; and a metal oxide coating the surface of the porous material. The thermal insulation material comprises a multilayer gradient phase change heat storage structure with gradually increasing melting point from outside to inside, a biomineralized inorganic framework, and a high-temperature activated self-repairing system. The multilayer gradient phase change heat storage structure comprises an outer layer, a middle layer, and an inner layer, the outer layer uses a low-melting-point phase change material with a melting point of 60-120℃, the middle layer uses a medium-melting-point phase change material with a melting point of 200-350℃, and the inner layer uses a high-melting-point phase change material with a melting point of 350-450℃. The biomineralized inorganic framework is formed by deposition of silicates and carbonates, and is converted into a ceramic phase at high temperature to limit the liquid flow of the phase change material. The high-temperature activated self-repairing system comprises self-repairing precursor compounds prepositioned in the biomineralized inorganic framework, which are activated under high-temperature conditions of fire and react with the surrounding mineralized framework to form a ceramic phase to repair material structure damage.

2. The thermal insulation material having fireproof and thermal insulation properties according to claim 1, characterized in that, The biomineralized inorganic framework is formed by the following steps: Mixing a sodium silicate solution and a calcium chloride solution in a molar ratio of 1:1.2, adding a mineralization inducer, and adjusting the pH to 8.0-8.5 to obtain a biomineralization reaction solution; Immersion of pretreated plant fibers and part of the phase change material in the mineralization reaction solution, stirring at 30-40℃ for 12-24 hours to form calcium silicate deposition; Adding a sodium carbonate solution to the system to form a composite mineralized layer of calcium carbonate deposition; Drying at 90-100℃ for 8-12 hours, followed by heat treatment at 200-250℃ for 2 hours to stabilize the inorganic framework structure.

3. The thermal insulation material having fireproof and thermal insulation properties according to claim 1, characterized by, The self-repairing precursor compounds comprise low-temperature activated precursors, medium-temperature activated precursors, and high-temperature activated precursors activated in sequence at different temperatures; The low-temperature activated precursors are activated at 300-400℃, the medium-temperature activated precursors are activated at 500-600℃, and the high-temperature activated precursors are activated at 700-800℃.

4. The thermal insulation material having fireproof and thermal insulation properties according to claim 3, characterized in that, The low-temperature activated precursors are aluminum phosphate, the medium-temperature activated precursors are aluminum borate, and the high-temperature activated precursors are aluminum hydroxide.

5. The thermal insulation material having fireproof and thermal insulation properties according to claim 1, characterized in that, The thermal insulation material further comprises a plant fiber and attapulgite composite reinforcing system; The plant fiber is subjected to alkali treatment activation, high-temperature carbonization pretreatment, and surface functional group grafting treatment, and the attapulgite is subjected to interlayer ion exchange, organic modification, and heat treatment activation.

6. The thermal insulation material having fireproof and thermal insulation properties according to claim 5, characterized in that, The plant fiber is selected from flax fiber, bamboo fiber, or straw fiber, and the surface functional group grafting treatment grafts carboxyl, hydroxyl, or amino functional groups on the surface of the plant fiber.

7. The thermal insulation material having fireproof and thermal insulation properties according to claim 6, characterized in that, The interlayer ion exchange of the attapulgite uses aluminum ion solution and magnesium ion solution, and the organic modification uses quaternary ammonium salt modifier or organosilane coupling agent.

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