Composite fire extinguishing agent and intelligent preparation method thereof

Abstract

The invention relates to the technical field of fire safety, and discloses a composite fire extinguishing agent and an intelligent preparation method thereof, and composite aerosol comprises an S-type aerosol generating agent and a perfluorohexanone microcapsule. The microcapsule has a double-layer wall material structure with perfluorohexanone as a core material, gelatin as an inner-layer wall material and a polyurea and montmorillonite nanocomposite as an outer-layer wall material, and presents bimodal particle size distribution. The preparation method comprises the following steps: preparing the microcapsule through a two-step emulsification and interfacial polymerization method; after the microcapsules and the S-type aerosol generating agent are mixed, an ignition layer, a composite main agent layer and a microcapsule enhancement layer are sequentially pressed by adopting a layered and differentiated pressure press-fitting process, and the grain is formed. Through the special structure of the microcapsule and precise control of the preparation process, the technical problems of high temperature of a traditional aerosol outlet and low utilization rate of clean gas are solved. The device has the beneficial effects that temperature response and staged release of the perfluorohexanone are realized, and the temperature of flue gas at an outlet is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fire safety, in particular to a composite fire extinguishing agent and an intelligent preparation method thereof. BACKGROUND

[0002] Gas fire extinguishing systems are widely used in electronic machine rooms, data centers, precision instrument rooms and other protected areas due to their advantages of leaving no residue after extinguishing and no pollution to equipment. However, traditional gas fire extinguishing systems usually require high-pressure storage containers and complex pipe network systems, which occupy a large space and have high installation and maintenance costs. As an alternative, thermal aerosol fire extinguishing technology has emerged, which generates a large number of fine solid particles and inert gases with extinguishing ability through the oxidation-reduction reaction of solid agents, and has the characteristics of small volume, no pressure storage, high extinguishing efficiency, etc.

[0003] However, the traditional S-shaped thermal aerosol fire extinguishing technology generates a large amount of heat during the release of the extinguishing medium due to the intense oxidation-reduction reaction of the generating agent, resulting in a smoke temperature at the nozzle of several hundred degrees Celsius or even thousands of degrees. This not only poses a risk of secondary damage to precision equipment and electronic components in the protected area, but also poses a potential threat to personnel safety. To solve the problem of high temperature and improve the overall extinguishing efficiency, existing technologies have attempted to physically compound the thermal aerosol generating agent with clean gas extinguishing agents such as perfluorohexone.

[0004] However, the existing composite technology still has inherent technical defects. In simple physical mixing or simple layered structure, the high temperature and high-speed airflow generated by the combustion of the aerosol generating agent can easily cause partial thermal cracking of the liquid perfluorohexone before it is vaporized, resulting in the ineffective consumption of the extinguishing agent and reducing its effective utilization rate and chemical inhibition efficiency in the fire scene. In addition, this one-time, uncontrolled mixing and release method cannot adjust the release rate and timing of the clean gas extinguishing agent according to different stages of fire development, making it difficult to maximize the extinguishing efficiency. At the same time, the direct contact between the liquid extinguishing agent and the solid powder during preparation and storage can also cause the migration, agglomeration or chemical property changes of the agent, affecting the long-term storage stability and performance reliability of the product.

[0005] Therefore, how to achieve efficient, controllable and phased release of clean gas extinguishing agents in the aerosol field while ensuring the stability and reliability of the preparation process of the composite extinguishing agent is a technical problem that needs to be solved in the current aerosol fire extinguishing technology field. SUMMARY

[0006] To address the shortcomings of existing technologies, this invention provides a composite fire extinguishing agent and its intelligent preparation method, which solves the problems of high spray temperature and easy secondary damage to equipment faced by existing thermal aerosol fire extinguishing technologies. Furthermore, when combined with clean gas fire extinguishing agents, the clean gas suffers from low utilization rate, uncontrollable release, and poor storage stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a composite fire extinguishing agent comprising a composite matrix uniformly mixed from an S-type aerosol generator and perfluorohexanone microcapsules; The perfluorohexanone microcapsules have a core-shell structure with a double-layered wall material. The core material is perfluorohexanone, the inner wall material is gelatin, and the outer wall material is a polyurea and montmorillonite nanocomposite material.

[0008] Preferably, the perfluorohexanone microcapsules have a bimodal particle size distribution, including fast-response microcapsules with a particle size of 50-100 μm and sustained-release microcapsules with a particle size of 150-200 μm, so as to realize intelligent and controllable release of perfluorohexanone at different stages of fire extinguishing.

[0009] Preferably, the S-type aerosol generator comprises, by mass percentage: 45% strontium nitrate, 15% potassium nitrate, 15% dicyandiamide, 5% phenolic resin, 3% potassium bicarbonate, 5% polyvinyl alcohol, and the balance being a catalyst and performance modifier.

[0010] Preferably, the catalyst is a transition metal oxide, used to promote the vaporization and dispersion of perfluorohexanone during the combustion of the S-type aerosol generator, thereby enhancing the synergistic fire extinguishing effect.

[0011] Preferably, the mass ratio of the perfluorohexanone microcapsules to the S-type aerosol generator is 2:8.

[0012] Preferably, the composite extinguishing agent is compressed into a granular structure with a layered structure, wherein the layered structure comprises, from the ignition end to the ejection end, an ignition layer, a composite main agent layer, and a perfluorohexanone microcapsule reinforcing layer; wherein the thickness of the ignition layer is 2.5±0.2mm, the thickness of the composite main agent layer is 44±1mm, and the thickness of the microcapsule reinforcing layer is 3.5±0.2mm.

[0013] A smart preparation method for a composite fire extinguishing agent includes the following steps: S1. Microcapsule preparation steps: The perfluorohexanone microcapsules with a double-layer wall material are prepared by combining a two-step emulsification method with an interfacial polymerization method. S2. Mixing step: The perfluorohexanone microcapsules are uniformly mixed with the S-type aerosol generator powder and surfactant to obtain a composite powder; S3. Pressing Step: Under controlled temperature and humidity conditions, a layered pressing process is used to press the composite powder and other components sequentially to form a drug column with an ignition layer, a composite main agent layer, and a perfluorohexanone microcapsule reinforcement layer.

[0014] Preferably, in the microcapsule preparation step S1, the two-step emulsification method specifically comprises: a first step of emulsification at a low speed of 500 rpm to form a crude emulsion, and a second step of emulsification at a high speed of 5000 rpm to form a fine emulsion; and the interfacial polymerization method is carried out under the conditions of temperature control at 45-55℃, pH value adjustment to 4.5-5.5, and reaction time of 3-4 hours.

[0015] Preferably, the microcapsule preparation step S1, after the interfacial polymerization is completed, further includes a post-processing step: filtering and washing the product, and then freeze-drying or spray-drying it to obtain perfluorohexanone microcapsule powder with good flowability.

[0016] Preferably, in the pressing step S3, the ignition layer, the composite agent layer, and the perfluorohexanone microcapsule reinforcement layer are pressed sequentially, wherein the pressing pressure of the ignition layer is 50 MPa, the pressing pressure of the composite agent layer is 80 MPa, the pressing pressure of the perfluorohexanone microcapsule reinforcement layer is 40 MPa, and the holding time for each layer is 20 to 30 seconds.

[0017] This invention provides a composite fire extinguishing agent and its intelligent preparation method. It has the following beneficial effects: 1. This invention, through the design of double-layer wall material and dual-peak particle size, makes the release of perfluorohexanone no longer random, but an intelligent response closely coupled with the fire extinguishing process, thus achieving precise fire extinguishing with initial cooling suppression and subsequent cleaning to prevent reignition.

[0018] 2. This invention provides the most suitable temperature and airflow fields for the release of perfluorohexanone through an optimized aerosol formulation. The added catalyst further enhances the chemical synergy between the two, resulting in a fire extinguishing efficiency of 1+1>2.

[0019] 3. This invention can stably control the outlet temperature below 150℃, significantly shortening the fire extinguishing time and leaving almost no residue in the space after fire extinguishing, making it extremely friendly to precision equipment.

[0020] 4. The process parameters optimized throughout the entire process set by this invention ensure stable product quality and good reproducibility, making it very suitable for large-scale industrial production and presenting a high technical barrier. Detailed Implementation

[0021] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example: Example 1: Preparation of perfluorohexanone microcapsules with double-layer wall material Inner layer (gelatin layer) coating: Dissolve 10g of gelatin in 100g of hot water at 60℃ to form aqueous phase I.

[0023] Mix 50g of perfluorohexanone with Span-80 as the oil phase.

[0024] The oil phase was slowly added to aqueous phase I under stirring at 500 rpm to form a crude emulsion. The emulsion was then cooled to below 10°C in an ice-water bath to gelatinize and initially encapsulate perfluorohexanone.

[0025] Outer layer (polyurea / montmorillonite layer): The above emulsion was poured into aqueous phase II containing 1g of organically modified nano-montmorillonite, 0.5g of emulsifier and 200g of water.

[0026] Emulsification at 5000 rpm for 15 minutes resulted in a stable fine emulsion.

[0027] Slowly add a mixed solution containing 5g of diethylenetriamine and 10g of diphenylmethane diisocyanate, and adjust the pH to 5.0 with acetic acid.

[0028] The reaction was carried out in a 50°C water bath for 3.5 hours to complete the interfacial polymerization of polyurea on the outer layer of the microcapsules.

[0029] Post-processing: After the reaction was completed, the mixture was filtered, washed with deionized water, and finally freeze-dried to obtain a highly free-flowing double-walled microcapsule powder. Analysis showed that the product exhibited a bimodal distribution, with peak values ​​at ~80 μm and ~180 μm, respectively.

[0030] Example 2: Preparation and Compression of Composite Fire Extinguishing Agent Preparation of S-type aerosol main agent: Accurately weigh the following components by mass ratio: 45% strontium nitrate, 15% potassium nitrate, 15% dicyandiamide, 5% phenolic resin, 3% potassium bicarbonate, 5% polyvinyl alcohol, 2% catalyst (manganese dioxide), with the remainder being potassium perchlorate as a regulator. Mix, pulverize, and pass through a 200-mesh sieve.

[0031] Composite powder mixing: The perfluorohexanone microcapsules prepared in Example 1 and the above-mentioned S-type aerosol main agent were added to a three-dimensional mixer at a mass ratio of 2:8, and 0.8% of OP-10 surfactant was added at the same time. The mixture was stirred at 30 rpm and an ambient temperature of 23°C for 2 hours until it was completely homogeneous.

[0032] Layered pressing: Operate in a constant temperature and humidity room with an ambient humidity of <35% and a temperature of 22℃.

[0033] A measured amount of igniter is loaded into the bottom of the mold and held at 50 MPa pressure for 25 seconds to form an ignition layer with a thickness of 2.5 mm.

[0034] A fixed amount of composite powder is added on top of the ignition layer, and the pressure is maintained at 80MPa for 30 seconds to form a composite main agent layer with a thickness of 44mm.

[0035] A quantitative amount of pure perfluorohexanone microcapsule powder was added on top of the composite main agent layer, and the mixture was held under pressure of 40 MPa for 20 seconds to form a microcapsule reinforcement layer with a thickness of 3.5 mm.

[0036] Demolding yields a dense, layered composite fire extinguishing agent column.

[0037] Example 3: Fire Extinguishing Performance Test and Comparison The testing method is the same as before. The results are compared below: Extinguishing time: The optimized solution of this invention shortens the extinguishing time to 10 seconds, while the traditional aerosol takes 18 seconds.

[0038] Exit flue gas temperature: The optimized solution of this invention reduces the maximum outlet temperature to 120℃, while the traditional aerosol temperature is 950℃.

[0039] Synergistic efficiency: Gas chromatography analysis showed that the effective utilization rate of perfluorohexanone in the fire scene was increased by about 40% in the present invention, proving the effectiveness of the catalyst and release design.

[0040] The above results show that the optimized scheme of the present invention has achieved a qualitative leap in all key performance indicators.

[0041] Test Example 1: Microcapsule morphology, particle size and heat release performance test Experimental steps: Microscopic morphology observation: A suitable amount of microcapsule samples from each group were sputtered with gold using an ion sputtering instrument. The surface morphology and structural integrity of the samples were observed and images were acquired using a scanning electron microscope at an accelerating voltage of 15kV.

[0042] Particle size distribution determination: Approximately 0.1 g of each group of microcapsule samples were dispersed in anhydrous ethanol and treated with an ultrasonic oscillator for 5 minutes to ensure uniform dispersion. The sample suspension was analyzed using a laser particle size analyzer, and the particle size distribution data were recorded.

[0043] Thermal release performance analysis: Each group of microcapsule samples was tested using a simultaneous thermal analyzer. 5–10 mg of sample was accurately weighed and placed in an alumina crucible. Under a nitrogen atmosphere, the temperature was increased from 30 °C to 600 °C at a rate of 10 °C / min. The thermogravimetric curve and differential scanning calorimetry curve of the sample mass as a function of temperature were recorded.

[0044] Experimental data: The data obtained from the above tests were organized, and the specific results are shown in Table 1.

[0045] Table 1. Comparison of microcapsule performance data: Analysis of experimental results: Table 1 shows the test data, revealing the direct impact of the microcapsule preparation process on its final structure and performance. The microcapsule sample prepared in Example 1 exhibited a complete spherical structure and a smooth surface under a scanning electron microscope. Its particle size distribution data clearly showed two separate peaks, located at 81.2 μm and 179.5 μm, forming a bimodal particle size distribution. In contrast, the sample in Comparative Example 3, due to room temperature drying, suffered from microsphere collapse and severe agglomeration caused by non-uniform solvent evaporation, making it impossible to obtain effective particle size distribution data. The sample in Comparative Example 2, due to a one-step high-speed emulsification process, failed to form uniformly sized droplet templates, resulting in an irregularly shaped final product with a single broad peak in particle size distribution. These results indicate that a two-step emulsification method is a necessary process condition for forming a bimodal particle size distribution, while freeze-drying is crucial for maintaining the complete spherical structure of the microcapsules.

[0046] Thermogravimetric analysis (TGA) results further clarified the correspondence between the wall structure of the microcapsules and their thermal release behavior. The sample from Example 1 exhibited two distinct mass loss stages on its TGA curve, starting at 165.3°C and 241.8°C, respectively. This corresponds to the structural characteristics of a bilayer wall material: the first stage of weight loss at lower temperatures is attributed to the thermal decomposition of the inner gelatin wall material, leading to the release of part of the core material; the second stage of weight loss at higher temperatures is attributed to the decomposition of the outer polyurea and montmorillonite nanocomposite wall material, which has better thermal stability. In contrast, the sample from Comparative Example 1, due to having only a single polyurea wall material, showed only a major mass loss stage around 238.5°C on its TGA curve, lacking release behavior in the low-temperature region. This comparison confirms that the bilayer wall material structure is the technical basis for achieving the staged temperature-responsive release of perfluorohexanone.

[0047] Based on comprehensive microstructure and thermal performance analysis, the perfluorohexanone microcapsules prepared in this technical solution exhibit a bimodal particle size distribution and a double-layer wall material structure, which together constitute their temperature-responsive release function. Under heating conditions, the smaller microcapsules heat up rapidly, and their inner gelatin wall material decomposes at a lower temperature, achieving an initial rapid release of the core material. Conversely, the larger microcapsules, with their higher thermal inertia, decompose at a higher temperature under the influence of their more heat-resistant outer wall material, achieving a sustained release of the core material. This combination of structure and performance allows the perfluorohexanone release process to match the temperature changes during fire extinguishing, thus providing material support for subsequent synergistic fire extinguishing effectiveness.

[0048] Test Example 2: Comparison Test of Extinguishing Agent Outlet Temperature Experimental steps: Test setup preparation: Fix the extinguishing agent charge to be tested on a special bracket inside a 1m³ sealed test chamber. Fix the measuring end of a K-type armored thermocouple 10cm from the extension line of the central axis of the charge nozzle.

[0049] Data acquisition start: Connect the thermocouple to the data acquisition system and set the acquisition frequency to 10Hz.

[0050] Ignition and Temperature Measurement of the Activated Fire Termite: The electric ignition device is activated to ignite the extinguishing agent termite. The data acquisition system simultaneously records the temperature change over time as measured by the thermocouple.

[0051] Data recording terminated: Data acquisition stopped after the propellant has completely burned and the nozzle temperature has continued to drop from its peak.

[0052] Data processing: Extract the highest temperature of the test from the collected temperature-time curve as the peak temperature.

[0053] Repeated testing: Repeat steps 1 to 5 above for each test object, and perform a total of 3 independent tests to obtain multiple sets of data.

[0054] Experimental data: The data obtained from the above tests were organized, and the specific results are shown in Table 2.

[0055] Table 2. Test data on peak temperature of extinguishing agent outlet: Analysis of experimental results: Table 2 shows that the extinguishing agents with different formulations exhibit significant differences in outlet temperature during combustion. The extinguishing agent column prepared according to Example 2 had an average peak outlet temperature of 120.4°C across three tests. In contrast, the extinguishing agent column prepared according to Comparative Example 5, which did not contain potassium bicarbonate, had an average peak outlet temperature of 495.6°C. The conventional S-type aerosol, however, reached an average peak outlet temperature of 953.2°C. The data indicates that adding potassium bicarbonate to the S-type aerosol generator reduced the peak outlet temperature by approximately 375°C.

[0056] The decrease in outlet temperature is due to the thermal decomposition of potassium bicarbonate added to the S-type aerosol generator formulation. During the combustion reaction of the aerosol generator, potassium bicarbonate undergoes primary and secondary endothermic decomposition upon heating, absorbing some of the heat generated by the combustion reaction. Its decomposition products include gases such as water vapor and carbon dioxide. These gases mix with the aerosol products, further reducing the temperature of the mixed flue gas through physical dilution. Therefore, the addition of potassium bicarbonate alters the overall thermodynamic properties of the aerosol generator, leading to a significant decrease in the final outlet temperature of its combustion products.

[0057] A low-temperature combustion system constructed by adding potassium bicarbonate to the S-type aerosol generator provides the necessary preconditions for the temperature-responsive release function of perfluorohexanone microcapsules. The temperature-suppressed, relatively mild aerosol field prevents the microcapsules from undergoing instantaneous, concentrated explosive decomposition due to exposure to excessively high initial temperatures. This allows the microcapsules, with their double-walled structure and bimodal particle size distribution, to release their core material in an orderly manner at different temperature stages of the fire extinguishing process, according to the temperature threshold set by their own structure. This achieves synergistic effects of initial cooling suppression and subsequent cleanup and reignition prevention, ensuring the overall effectiveness of the composite fire extinguishing agent design.

[0058] Test Example 3: Comparison Test of Fire Extinguishing Efficiency and Coordination Efficiency Experimental steps: Ignition source and environmental preparation: In a closed test space with a volume of 27m³, place a 30cm diameter oil pan containing 2L of n-heptane at the center of the ground. Fix the extinguishing agent column to be tested on a support 1.5m horizontally and 1.2m vertically from the center of the oil pan.

[0059] Gas sampling and analysis preparation: Fix the inlet end of the gas sampling tube at the geometric center of the test space, and connect the outlet end to the injection valve of the gas chromatograph.

[0060] Ignition and pre-ignition: Ignite the n-heptane in the fuel pan and allow it to burn freely for 60 seconds to form a stable flame.

[0061] Extinguishing and Timing: The extinguishing agent cartridge is electrically activated, simultaneously starting the timer. The timer stops when the flames in the oil pan are completely invisible, and the extinguishing time is recorded.

[0062] Sampling and Analysis: Within 5 seconds of flame extinguishing, start the sampling pump to extract 100 mL of the mixed gas from the test space and inject it into the gas chromatograph. Analyze the sample under preset chromatographic conditions to determine the concentration of undecomposed perfluorohexanone gas.

[0063] Utilization rate calculation: Based on the total mass of perfluorohexanone in the propellant column and the test space volume, the theoretical maximum gas concentration is calculated. The effective utilization rate of perfluorohexanone is then calculated by comparing the measured concentration with the theoretical maximum concentration.

[0064] Repeated testing: Repeat steps 1 to 6 above for each test subject, and perform a total of 3 independent tests.

[0065] Experimental data: The data obtained from the above tests were organized, and the specific results are shown in Table 3.

[0066] Table 3. Test data on fire extinguishing performance and synergistic efficiency: Analysis of experimental results: Table 3 shows that different formulations and structures of extinguishing agents exhibit clear differences in both extinguishing time and perfluorohexanone utilization rate. The average extinguishing time of the sample in Example 2 was 10.1 seconds, significantly shorter than that of Comparative Example 4 and Comparative Example 8. Regarding utilization rate, the average value of the sample in Example 2 was 70.5%, compared to 62.1% and 50.1% for Comparative Example 4 and Comparative Example 8, respectively. The data indicate that the presence of a catalyst in the S-type aerosol generator and the addition of perfluorohexanone in microencapsulated form both have a direct positive impact on extinguishing efficiency.

[0067] The mechanism by which the catalyst affects the fire extinguishing process is manifested in its promoting effect on the vaporization and dispersion of perfluorohexanone. In Example 2, within the heat and airflow field generated by the combustion of the S-type aerosol generator, the dispersed transition metal oxide catalyst particles provide a highly active surface for perfluorohexanone released from the microcapsules. Adsorption of perfluorohexanone at these catalytically active sites lowers the activation energy required for its phase transition, accelerating its transformation from liquid to gas. This accelerated process leads to a rapid accumulation of perfluorohexanone vapor concentration and a significant physical endothermic cooling effect within the fire extinguishing space. Compared to Comparative Example 4 without a catalyst, this accelerated vaporization and more uniform dispersion allow the chemical inhibition and physical cooling effects of the extinguishing agent to reach the fire extinguishing threshold more quickly, thereby shortening the extinguishing time.

[0068] The mechanism by which the microcapsule structure affects the effective utilization rate of perfluorohexanone lies in its physical isolation of the core material and its time-sequential release function. In Comparative Example 8, liquid perfluorohexanone was directly mixed with S-type aerosol generator powder. During the combustion of the agent, some perfluorohexanone was directly exposed to the high-temperature reaction zone of the solid combustion layer, resulting in ineffective thermal decomposition and destruction of its molecular structure as an extinguishing agent. In Example 2, however, perfluorohexanone was encapsulated within a thermally stable double-layer wall material. This wall material structure acted as a thermal barrier, allowing most of the core material to remain intact in the early stages of combustion. As the temperature increased, the microcapsule wall material ruptured according to its set thermal decomposition temperature, releasing the liquid perfluorohexanone into the relatively cooler gas phase flow field for vaporization, rather than decomposing in the solid phase combustion zone. This mechanism reduces the ineffective thermal decomposition loss of perfluorohexanone, allowing it to participate in the gas phase extinguishing process in a more intact molecular form, ultimately resulting in a higher effective utilization rate.

[0069] Test Example 4: Comparison Test of Propellant Column Structure and Combustion Stability Experimental steps: Structural integrity test: Each group of propellant samples was dropped freely from a height of 1.5m onto a horizontal cement floor. After the free fall, the appearance of the propellant was visually inspected and recorded to determine whether there were any structural damage phenomena such as cracks, delamination, or breakage.

[0070] Combustion process observation: The propellant charge to be tested is vertically fixed on the combustion test stand. A high-speed camera with a frame rate of 1000fps is used to record images of the entire process from ignition to the end of combustion.

[0071] Ignition and Data Recording: The propellant is ignited by an electric ignition device that contacts the ignition layer of the propellant. By analyzing images recorded by a high-speed camera, the ignition delay time from the energization of the electric ignition device to the appearance of a sustained flame on the propellant body is measured, and the phenomena of the entire combustion process are observed and recorded, including the smoothness of flame propagation, whether there is deflagration or interruption of combustion, etc.

[0072] Residue observation: After the combustion of the propellant has completely stopped, observe and record the morphology of the residue.

[0073] Repeated testing: Repeat steps 1 to 4 above for each test object, and perform a total of 3 independent tests.

[0074] Experimental data: The data obtained from the above tests were organized, and the specific results are shown in Table 4.

[0075] Table 4. Test data on propellant grain structure and combustion stability: Analysis of experimental results: The test data in Table 4 show that different pressing processes have a decisive impact on the mechanical properties and combustion behavior of the propellant grains. The propellant grain of Example 2 exhibits good structural strength and a stable, controllable combustion process. The propellant grain of Comparative Example 6 has low mechanical strength, is difficult to ignite, and exhibits an extremely unstable combustion process. Although the propellant grain of Comparative Example 7 can burn stably, its behavior in the early stages of combustion is abnormal, and the morphology of the residue indicates that its functional layer may have failed.

[0076] The failures of Comparative Examples 6 and 7 can be explained by inherent defects in their press-packing processes. In Comparative Example 6, the igniter, S-type aerosol generator, and perfluorohexanone microcapsules were mixed and press-packed together, resulting in mutual dilution of the components. The decrease in igniter concentration increased its ignition threshold energy, causing ignition delay or even failure. Simultaneously, the uneven density distribution within the propellant grain created an unstable combustion wave front, leading to intermittent and incomplete combustion. In Comparative Example 7, although a layered structure was used, applying a uniform 80 MPa pressure to all layers exceeded the mechanical strength limit of the perfluorohexanone microcapsules. Especially in the reinforcing layer composed of pure microcapsules, the high pressure caused numerous microcapsules to rupture, resulting in the leakage of perfluorohexanone before combustion. This prematurely released perfluorohexanone rapidly vaporized upon heating in the early stages of combustion, causing intense initial combustion and detonation sounds, indicating that its temperature-controlled release function had failed.

[0077] The precision layered pressing process employed in this technical solution solves the aforementioned problems by setting differentiated pressing pressures for different functional layers. First, the layered structure ensures the purity and distribution of each functional component: the ignition layer guarantees reliable ignition with low delay; the composite agent layer provides energy for the main reaction; and the perfluorohexanone microcapsule reinforcement layer serves as a functional reserve for subsequent reignition prevention. Second, differentiated pressing pressures are necessary to maximize the function of each layer: a moderate pressure is applied to the ignition layer to obtain the appropriate porosity required for ignition; a high pressure is applied to the composite agent layer to form a high-density propellant, ensuring stable burning rate and energy output; and a low pressure is applied to the perfluorohexanone microcapsule reinforcement layer—pressure sufficient to form the microcapsule powder but below its structural damage threshold. This process ensures the structural integrity of the microcapsules during manufacturing and storage, thereby guaranteeing their sequential release under the designed temperature response during actual fire extinguishing operations.

Claims

1. A composite fire extinguishing agent, characterized in that, It includes a composite matrix composed of a uniformly mixed S-type aerosol generator and perfluorohexanone microcapsules; The perfluorohexanone microcapsules have a core-shell structure with a double-layered wall material. The core material is perfluorohexanone, the inner wall material is gelatin, and the outer wall material is a polyurea and montmorillonite nanocomposite material.

2. The composite fire extinguishing agent according to claim 1, characterized in that, The perfluorohexanone microcapsules have a bimodal particle size distribution, including fast-response microcapsules with a particle size of 50-100 μm and sustained-release microcapsules with a particle size of 150-200 μm, enabling intelligent and controllable release of perfluorohexanone at different stages of fire extinguishing.

3. The composite fire extinguishing agent according to claim 1, characterized in that, The S-type aerosol generator comprises, by mass percentage: 45% strontium nitrate, 15% potassium nitrate, 15% dicyandiamide, 5% phenolic resin, 3% potassium bicarbonate, 5% polyvinyl alcohol, and the balance being catalyst and performance modifier.

4. The composite fire extinguishing agent according to claim 3, characterized in that, The catalyst is a transition metal oxide, used to promote the vaporization and dispersion of perfluorohexanone during the combustion of the S-type aerosol generator, thereby enhancing the synergistic fire extinguishing effect.

5. The composite fire extinguishing agent according to claim 1, characterized in that, The mass ratio of the perfluorohexanone microcapsules to the S-type aerosol generator is 2:

8.

6. The composite fire extinguishing agent according to claim 1, characterized in that, The composite extinguishing agent is compressed into a granular structure with a layered structure. The layered structure, from the ignition end to the ejection end, includes an ignition layer, a composite main agent layer, and a perfluorohexanone microcapsule reinforcement layer in sequence. The thickness of the ignition layer is 2.5±0.2 mm, the thickness of the composite main agent layer is 44±1 mm, and the thickness of the microcapsule reinforcement layer is 3.5±0.2 mm.

7. An intelligent preparation method for a composite fire extinguishing agent, wherein the composite fire extinguishing agent according to any one of claims 1-6 is characterized in that, Includes the following steps: S1. Microcapsule preparation steps: The perfluorohexanone microcapsules with a double-layer wall material are prepared by combining a two-step emulsification method with an interfacial polymerization method. S2. Mixing step: The perfluorohexanone microcapsules are uniformly mixed with the S-type aerosol generator powder and surfactant to obtain a composite powder; S3. Pressing Step: Under controlled temperature and humidity conditions, a layered pressing process is used to press the composite powder and other components sequentially to form a drug column with an ignition layer, a composite main agent layer, and a perfluorohexanone microcapsule reinforcement layer.

8. The intelligent preparation method of a composite fire extinguishing agent according to claim 7, characterized in that, In the microcapsule preparation step S1, the two-step emulsification method specifically comprises: firstly, emulsification at a low speed of 500 rpm to form a coarse emulsion, and secondly, emulsification at a high speed of 5000 rpm to form a fine emulsion; and the interfacial polymerization method is carried out under the conditions of temperature control at 45-55℃, pH value adjustment to 4.5-5.5, and reaction time of 3-4 hours.

9. The intelligent preparation method of a composite fire extinguishing agent according to claim 7, characterized in that, The microcapsule preparation step S1, after the interfacial polymerization method is completed, also includes a post-processing step: filtering and washing the product, and then freeze-drying or spray-drying it to obtain perfluorohexanone microcapsule powder with good flowability.

10. The intelligent preparation method of a composite fire extinguishing agent according to claim 7, characterized in that, In the pressing step S3, the ignition layer, the composite agent layer, and the perfluorohexanone microcapsule reinforcement layer are pressed sequentially. The pressing pressure of the ignition layer is 50 MPa, the pressing pressure of the composite agent layer is 80 MPa, and the pressing pressure of the perfluorohexanone microcapsule reinforcement layer is 40 MPa. The holding time for each layer is 20 to 30 seconds.

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