Fire extinguishing microcapsules and microfluidic controllable preparation method thereof

Abstract

This invention belongs to the field of fire extinguishing materials and their preparation technology, and provides a fire extinguishing microcapsule and its microfluidic controllable preparation method. The preparation method is characterized by the following steps: (1) preparing fluids of each phase, (2) preparing a dual emulsion using a microfluidic device, (3) collecting and sealing the dual emulsion in a collection container, controlling the axis of the collection container to be horizontal, and controlling the collection container to rotate around its axis for 1 to 15 minutes, applying light to solidify the outer shell of the dual emulsion droplets while maintaining the rotation of the collection container, cleaning, and drying to obtain the final product. The fire extinguishing microcapsule prepared by this method consists of an outer shell and a liquid fluorine-containing fire extinguishing agent encapsulated within the outer shell. The outer shell of the fire extinguishing microcapsule has a uniform thickness, and the eccentricity between the outer shell and the core is less than 0.1. The method of this invention can achieve precise customization of fire extinguishing microcapsules according to the differentiated fire characteristics of different application scenarios, and can improve the concentricity between the core and the outer shell of existing fire extinguishing microcapsules.

Description

Technical Field

[0001] This invention belongs to the field of fire extinguishing materials and their preparation technology, and relates to a fire extinguishing microcapsule and its microfluidic controllable preparation method. Background Technology

[0002] Fires are unpredictable and among the most common disasters, posing a significant threat to public safety and social progress. This threat is particularly pronounced in confined spaces where fires are difficult to detect in time, and the accumulation of heat and toxic fumes exacerbates the combustion process. Therefore, early detection of initial signs of fire and swift implementation of firefighting measures are crucial.

[0003] Microencapsulation technology, serving as the first line of fire protection, has garnered significant attention for eliminating fire hazards. Fire extinguishing microcapsules are core-shell structured fire extinguishing materials with a polymer shell and a fire extinguishing agent core. When the shell ruptures at a certain temperature, the encapsulated fire extinguishing agent is released, extinguishing early-stage fires. Fire extinguishing microcapsules possess a unique response mechanism to heat stimulation, triggering the release of the internal fire extinguishing agent through temperature changes, endowing them with many superior properties not found in conventional core-shell microcapsules.

[0004] For electrical fires, traditional extinguishing agents, such as dry powder, carbon dioxide, and aerosol extinguishing agents, can only extinguish the apparent flames that appear after thermal runaway (TR) and cannot function in the early stages of the TR reaction. Fluorine-containing extinguishing agents, such as perfluorohexanone, possess excellent properties such as non-conductivity, volatility, no residue, easy photolysis, zero ozone depletion, and low global warming potential. They can produce highly effective fire extinguishing through a combination of physical cooling and chemical inhibition.

[0005] Currently, the main methods for preparing fire extinguishing microcapsules include in-situ polymerization, interfacial polymerization, composite gelation, and microfluidic methods. Due to the poor solubility and high volatility of fluorinated fire extinguishing agents, traditional microcapsule solidification methods face significant challenges in terms of encapsulation efficiency, uniformity, controllability, and processing costs. Microfluidic methods, which enable the controllable preparation of uniform emulsions, have received increasing attention in the field of fire extinguishing microcapsule preparation in recent years. For liquid fluorinated fire extinguishing agents, their density is relatively high (for example, at normal temperature and pressure, the density of perfluorohexanone is 1.60 g / cm³, the density of hexafluoropropane is 1.37 g / cm³, and the density of perfluoropolyether is between 1.80 and 1.92 g / cm³). Although microfluidic methods can be used to prepare emulsion templates with relatively uniform dimensions, the high density of the liquid fluorinated fire extinguishing agent used as the core material often leads to core material eccentricity during the curing process. This results in poor concentricity between the shell and the core material of the prepared fire extinguishing microcapsule, with the shell on the eccentric side being very thin and having poor mechanical properties. This creates a weak point in the mechanical properties of the fire extinguishing microcapsule, making it easy for the fire extinguishing agent to prematurely rupture the shell from the area with the thinner shell and leak out. Meanwhile, considering the differentiated fire characteristics of various application scenarios such as lithium battery compartments, precision electrical components, and sealed cavities, customizing the mechanical strength, thermal response temperature, and rupture threshold of fire extinguishing microcapsules is crucial to ensuring accurate release of extinguishing agents in different fire scenarios. Therefore, developing a method for preparing fire extinguishing microcapsules that facilitates systematic and coordinated control of the core component system and key geometric parameters, and addresses the issue of eccentricity of liquid fluorinated extinguishing agent core materials within the microcapsule, will have a positive impact on achieving precise customized design of fire extinguishing microcapsules, improving their overall performance, and promoting the application of microencapsulated fluorinated extinguishing agents. Summary of the Invention

[0006] To achieve precise control of the performance of fire extinguishing microcapsules based on the differentiated fire characteristics of different application scenarios, and to solve the core material eccentricity problem of fire extinguishing microcapsules prepared by existing technologies, this invention provides a fire extinguishing microcapsule and its microfluidic controllable preparation method. This method enables precise customization of fire extinguishing microcapsules based on the differentiated fire characteristics of different application scenarios and effectively improves the concentricity between the core and shell of existing fire extinguishing microcapsules.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0008] A microfluidic controllable preparation method for fire extinguishing microcapsules includes the following steps:

[0009] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0010] A liquid fluorine-containing fire extinguishing agent is used as the inner phase fluid; a photoinitiator is fully dispersed or dissolved in a liquid photocurable polymer monomer to obtain an intermediate phase fluid, wherein the concentration of the photoinitiator in the intermediate phase fluid is 0.5 wt%~2.5 wt%; a surfactant is dissolved in water to obtain an outer phase fluid, wherein the concentration of the surfactant in the outer phase fluid is 1 wt%~5 wt%; the inner phase fluid and the intermediate phase fluid are immiscible.

[0011] (2) Preparation of double emulsion

[0012] The inner phase fluid is introduced into the injection tube of the coaxial capillary microfluidic device, and the intermediate phase fluid and the outer phase fluid are introduced into the collection tube of the coaxial capillary microfluidic device. A monodisperse oil-in-water emulsion is formed in the collection tube. The emulsion is collected in a collection container containing the outer phase fluid. The main body of the collection container is cylindrical and made of a light-transmitting material.

[0013] (3) Preparation of fire extinguishing microcapsules

[0014] Seal the collection container, keep its axis horizontal, and rotate it around its axis for 1-15 minutes. While keeping the container rotating, apply light to it to induce photo-crosslinking of the photocurable polymer monomers in the double emulsion droplets until the outer shell of the double emulsion droplets is cured. Then clean and dry to obtain the fire extinguishing microcapsules.

[0015] In step (3) of the above preparation method, the rotation speed of the collection container around the axis of the collection container is controlled to be 15~100 rpm.

[0016] In step (3) of the above preparation method, a feasible method for controlling the rotation of the collection container around the axis of the collection container is: placing the collection container on a rotating platform with the axis of the collection container parallel to the horizontal plane, and using the rotating platform to drive the collection container to rotate around the axis of the collection container.

[0017] In step (3) of the above preparation method, when applying light to the collection container, the position and form of the light source are controlled so that the surface of the collection container receiving light can receive uniform light. One feasible method for applying light is to apply ultraviolet light to the collection container from above or the side while keeping the collection container rotating.

[0018] In step (3) of the above preparation method, the light exposure time is usually 1 to 10 minutes, which can solidify the shell of the double emulsion droplet.

[0019] In step (3) of the above preparation method, when the total volume of the external phase fluid and the dual emulsion in the collection container reaches 85%~100% of the volume of the collection container, the collection container is sealed.

[0020] In step (1) of the above preparation method, the liquid fluorinated fire extinguishing agent refers to a fluorinated fire extinguishing agent that is liquid at room temperature and pressure. Common liquid fluorinated fire extinguishing agents include perfluorohexanone, hexafluoropropane, perfluoropolyether (PFPE) liquid fluorinated fire extinguishing agents, etc.

[0021] In step (1) of the above preparation method, the photocurable polymer monomer is an acrylate photocurable polymer monomer. Further, the acrylate photocurable polymer monomer refers to a photocurable polymer monomer containing an acrylate double bond (CH2=CH-COO-) that can initiate free radical polymerization upon ultraviolet light irradiation in the presence of a photoinitiator. Feasible acrylate photocurable polymer monomers include monofunctional acrylate monomers, difunctional acrylate monomers, trifunctional and polyfunctional acrylate monomers.

[0022] For example, the monofunctional acrylate monomer can be isobornyl acrylate (IBOA), isooctyl acrylate (2-EHA), hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), acrylmorpholine (ACMO), lauryl acrylate (LA), tetrahydrofuran acrylate (THFA), etc.

[0023] For example, the bifunctional acrylate monomer can be 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate (NPGDA), polyethylene glycol diacrylate (PEGDA), ethoxylated bisphenol A diacrylate (Bis-EOTA), etc.

[0024] For example, the trifunctional and polyfunctional acrylate monomers may be trimethylolpropane triacrylate (TMPTA), propoxylated glycerol triacrylate (GPTA), pentaerythritol triacrylate (PETA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol hexaacrylate (DPHA), ethoxylated trimethylolpropane triacrylate (EO-TMPTA), etc.

[0025] In the above preparation method, the photoinitiator in step (1) is a free radical ultraviolet photoinitiator, which can be a commonly used free radical ultraviolet photoinitiator in the prior art. For example, the photoinitiator can be 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP).

[0026] In step (1) of the above preparation method, in order to improve the thermal stability and flame retardant performance of the fire extinguishing microcapsule shell and delay the thermal decomposition and combustion of the fire extinguishing microcapsule shell, flame retardant materials are also dispersed or dissolved in the intermediate phase fluid. Feasible flame retardant materials include phosphorus-based flame retardants, and other flame retardant materials are also possible. Further, the content of the phosphorus-based flame retardant in the intermediate phase fluid can be 5 wt% to 15 wt%.

[0027] In step (1) of the above preparation method, the surfactant is a water-soluble surfactant. Typically, the surfactant can be polyvinyl alcohol (PVA), sodium dodecyl sulfate (SDS), or polysorbate-20 (Tween-20).

[0028] In step (2) of the above preparation method, the flow rate ratio of the inner phase fluid, the intermediate phase fluid and the outer phase fluid is controlled to be (20~140):(25~230):(80~1500).

[0029] In step (2) of the above preparation method, the method for preparing the water-in-oil-in-oil dual emulsion using a microfluidic device can refer to existing technologies. A feasible operation method is as follows: First, the external phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using an injection pump to wet the collection tube. Then, the intermediate phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using an injection pump until a stable water-in-oil (O2 / W) monoemulsion can be formed in the collection tube. Then, the internal phase fluid is injected into the injection tube of the coaxial capillary microfluidic device using an injection pump to form a monodisperse water-in-oil-in-oil (O1 / O2 / W) dual emulsion in the collection tube. The dual emulsion is collected using a collection container containing the external phase fluid.

[0030] In step (2) of the above preparation method, the coaxial capillary microfluidic device consists of an injection tube, a connecting tube, and a receiving tube. The outlet of the injection tube is tapered. The outlet end of the injection tube is inserted into the inlet end of the collecting tube and connected through the connecting tube. The injection tube, connecting tube, and collecting tube are coaxially arranged. An intermediate phase fluid inlet and an outer phase fluid inlet are provided at the inlet end of the connecting tube. Typically, the inner diameter of the tapered opening of the injection tube is 60~400 μm, and the inner diameter of the receiving tube is 100~900 μm.

[0031] In the above-described preparation method, the particle size and shell thickness of the prepared fire extinguishing microcapsules can be controlled by adjusting one or more of the channel dimensions (e.g., the inner diameter of the conical opening of the injection tube and the inner diameter of the receiving tube) and the flow rates of each phase fluid in the coaxial capillary microfluidic device. The shell material of the fire extinguishing microcapsules can be controlled by adjusting the type of photocurable polymer monomers and / or flame-retardant materials in the intermediate phase fluid. Through these adjustments, precise control of the mechanical properties and thermal response temperature of the fire extinguishing microcapsules can be achieved. Furthermore, the fire extinguishing effect of the fire extinguishing microcapsules can also be controlled by adjusting the specific type of liquid fluorinated fire extinguishing agent.

[0032] The present invention also provides a fire extinguishing microcapsule prepared by the above method, which consists of an outer shell and a liquid fluorinated fire extinguishing agent encapsulated within the outer shell. The outer shell of the fire extinguishing microcapsule has a uniform thickness. The outer shell is made of a photocurable polymer, or a combination of a photocurable polymer and a flame-retardant material.

[0033] In the above-mentioned technical solution for fire extinguishing microcapsules, the eccentricity (core-shell structure eccentricity) between the outer shell and the core of the fire extinguishing microcapsule is less than 0.1. The calculation method for the eccentricity between the outer shell and the core of the fire extinguishing microcapsule is as follows:

[0034] First, the microscopic images of the fire extinguishing microcapsules were fitted to obtain the outline circles of the core and outer shell of the fire extinguishing microcapsules, and then the center coordinates (X, Y) of the core were obtained. core ,Y core ) and the center coordinates of the outer shell (X shell ,Y shell Then, based on the Euclidean distance formula in the two-dimensional plane... First, calculate the straight-line distance (center distance) d between the center of the core and the center of the outer shell. Then, normalize the calculated center distance d: using the radius of the fitted circle of the fire extinguishing microcapsule core profile as a reference, divide the center distance d by the outer shell radius. The eccentricity of the fire extinguishing microcapsule shell and core was obtained.

[0035] In the above-mentioned technical solution of fire extinguishing microcapsules, the outer diameter of the fire extinguishing microcapsules can be determined according to the actual application requirements, and is usually 100~900 μm.

[0036] In the above-mentioned technical solution of fire extinguishing microcapsules, the thickness and material of the outer shell of the fire extinguishing microcapsule will affect the mechanical properties of the outer shell. In practical applications, the thickness and material of the outer shell can be adjusted according to the requirements of the mechanical properties of the outer shell. Typically, the outer shell thickness of the fire extinguishing microcapsule is 1~100 μm, and the ratio of the outer shell thickness to the outer diameter of the fire extinguishing microcapsule is (0.01~0.6):1.

[0037] In the aforementioned technical solution for fire extinguishing microcapsules, precise control of the mechanical properties of the fire extinguishing microcapsules can be achieved by adjusting the outer shell material and geometric dimensions (particle size, shell thickness, concentricity). In practical applications, depending on the fire characteristics of the application scenario, the performance of the fire extinguishing microcapsules can be precisely matched by adjusting the outer shell material and geometric structure. Typically, the thermal response temperature range of the fire extinguishing microcapsules is 80~250 ℃.

[0038] The fire extinguishing microcapsules provided by this invention can be used for fire extinguishing and fire prevention in small, enclosed spaces (such as electrical boxes or batteries).

[0039] Compared with the prior art, the technical solution of the present invention can produce the following beneficial technical effects:

[0040] 1. This invention provides a microfluidic controllable preparation method for fire extinguishing microcapsules. The method uses a liquid fluorinated fire extinguishing agent as the inner phase fluid, a liquid photocurable polymer monomer containing a photoinitiator or a photoinitiator and flame retardant material as the intermediate phase fluid, and an aqueous solution of a surfactant as the outer phase fluid. A coaxial capillary microfluidic device is used to shear the mixture in one step to form a monodisperse oil-in-water double emulsion. The double emulsion is collected in a collection container containing a collection liquid. The collection container is then sealed, its axis is kept horizontal, and the container is rotated around its axis. When the core and shell of the double emulsion droplets are concentric, light is applied to the collection container while it remains rotated. This causes photocrosslinking of the photocurable polymer monomers in the double emulsion droplets, solidifying the shell of the droplets. After cleaning and drying, the fire extinguishing microcapsules are obtained. The method of this invention overcomes the problem of large density differences between the core and shell of the dual emulsion, which easily leads to eccentricity under gravity, by applying a rotational operation to the dual emulsion droplets and controlling the photocrosslinking speed. This ensures high concentricity between the core and shell during photo-initiated curing, ultimately resulting in fire extinguishing microcapsules with uniform shell thickness. This invention solves the eccentricity problem of fire extinguishing microcapsules prepared by existing technologies. Increased concentricity between the core and shell improves the overall mechanical properties of the fire extinguishing microcapsule, fundamentally preventing premature leakage of the extinguishing agent, improving the consistency of the triggering conditions for the release of the extinguishing material within the microcapsule, and enhancing the fire extinguishing effect.

[0041] 2. The microfluidic controllable preparation method for fire extinguishing microcapsules provided by this invention, through the synergistic regulation of the component system and geometric parameters (particle size, shell thickness, and concentricity) of the fire extinguishing microcapsules, can achieve precise control over the mechanical properties, thermal response temperature, and rupture threshold of the microcapsules. Therefore, based on the differentiated fire characteristics of different application scenarios such as lithium battery compartments, precision electrical components, and sealed cavities, by adjusting the shell and core material compositions and the geometric dimensions of the fire extinguishing microcapsules, customized and matched performance parameters (mechanical properties, thermal response temperature, and rupture threshold) can be achieved, enabling on-demand, near-source, and precise release of the extinguishing agent, thereby effectively improving fire suppression efficiency.

[0042] 3. The microfluidic controllable preparation method for fire extinguishing microcapsules provided by this invention, through synergistic optimization of the capsule shell material selection and thickness, overall microcapsule particle size, and concentricity of the core and shell materials, and further by introducing flame-retardant materials into the shell material, enables precise and controllable release of the fire extinguishing agent within the microcapsule over a wide temperature range. For example, experiments have demonstrated that by adjusting the shell material and geometric parameters of the fire extinguishing microcapsule, the thermal response temperature of the fire extinguishing microcapsule can be controlled within a temperature range of 80~250 ℃. For small-scale fire scenarios, relying on the aforementioned precise control effect, directional and efficient release of the fire extinguishing agent can be achieved, avoiding the problem of premature or delayed release, effectively improving fire extinguishing efficiency and reducing fire extinguishing agent loss, thus reducing unnecessary damage to the surrounding environment. Furthermore, the shell material selected in this invention possesses excellent thermal stability and mechanical properties. Combined with precise control of the mechanical properties of the fire extinguishing microcapsule, it can ensure timely release of the fire extinguishing agent during a fire, and prevent rupture and leakage of the microcapsule during storage and transportation, improving the storage safety and reliability of the product.

[0043] 4. The microfluidic controllable preparation method for fire extinguishing microcapsules provided by this invention allows for precise control of the size and shell thickness of the dual emulsion template by adjusting the flow rate of the three-phase fluid and the channel size of the microfluidic device. Furthermore, by rotating the collection container holding the dual emulsion template and applying light, the dual emulsion template is solidified, resulting in fire extinguishing microcapsules with uniform size, controllable structure, and uniform shell thickness. Compared to existing technologies, this method effectively improves the preparation efficiency of fire extinguishing microcapsules, as well as the encapsulation efficiency, uniformity, controllability, and processing cost of fire extinguishing materials.

[0044] 4. This invention also provides a fire extinguishing microcapsule prepared by the above-described method. The microcapsule consists of an outer shell and a liquid fluorinated fire extinguishing agent encapsulated within the outer shell, with a uniform outer shell thickness. By improving the concentricity of the core and the outer shell, this invention solves the problem of high-density liquid fluorinated fire extinguishing agents being difficult to encapsulate efficiently and having a low encapsulation rate. Attached Figure Description

[0045] Figure 1This is a schematic diagram of a primary microfluidic device. The reference numerals are as follows: 1 is the injection tube, 2 is the connecting tube, and 3 is the collection tube.

[0046] Figure 2 This is a schematic diagram of the preparation of fire extinguishing microcapsules by dual emulsion droplet rotation photocuring according to the present invention. The reference numerals are as follows: 4 is the collection container, and 5 is the ultraviolet lamp.

[0047] Figure 3 This is an optical micrograph of the double emulsion droplets after rotating for 10 minutes in step (3) of Example 1.

[0048] Figure 4 This is an optical micrograph of the fire extinguishing microcapsules prepared in Example 1.

[0049] Figure 5 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 1.

[0050] Figure 6 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 2.

[0051] Figure 7 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 3.

[0052] Figure 8 This is an optical micrograph of the double emulsion droplets after rotating for 10 minutes in step (3) of Example 2.

[0053] Figure 9 This is an optical micrograph of the fire extinguishing microcapsules prepared in Example 2.

[0054] Figure 10 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 4.

[0055] Figure 11 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 5.

[0056] Figure 12 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 6.

[0057] Figure 13 These are the force-displacement curves of fire extinguishing microcapsules with different shell materials prepared in Example 5.

[0058] Figure 14 These are the thermogravimetric test results of fire extinguishing microcapsules of different sizes prepared in Example 6.

[0059] Figure 15 These are the thermogravimetric test results of fire extinguishing microcapsules with different shell materials prepared in Example 6. Detailed Implementation

[0060] The following embodiments further illustrate the fire extinguishing microcapsules and their microfluidic controllable preparation method described in this invention. It should be noted that the following embodiments are only for further illustration of this invention and should not be construed as limiting the scope of protection of this invention. Any non-essential improvements and adjustments made to this invention by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0061] In the following embodiments and comparative examples, the coaxial capillary microfluidic device used is a first-stage microfluidic device, and its structure is as follows: Figure 1 As shown, the device includes an injection tube 1, a connecting tube 2, and a collection tube 3, and is used in conjunction with an injection pump. The injection tube is made of a cylindrical glass capillary tube with an outer diameter of 960 μm and an inner diameter of 550 μm in its cylindrical section. The tail of the cylindrical glass capillary tube is drawn into a conical shape using a needle puller, and then polished on sandpaper until the inner diameter of the conical opening is approximately 60-400 μm, which is the outlet of the injection tube. The collection tube is also made of a cylindrical glass capillary tube, with both ends polished smooth. The outer diameter of the collection tube is 960 μm, and the inner diameter is 100-900 μm. The connecting tube is a square glass tube, with both ends polished smooth. A square through-hole with a size of 1.0 × 1.0 mm is located in the center. After fabrication, the injection tube, connecting tube, and collection tube are ultrasonically cleaned in anhydrous ethanol and then dried. The outlet end of the injection tube is inserted into the inlet end of the collection tube and connected via a connecting tube. The injection tube, connecting tube, and collection tube are coaxially arranged and fixed to the glass slide with AB glue. A flat-headed needle (for introducing the inner phase fluid) is fixed to the inlet end of injection tube 1 with AB glue, and two flat-headed needles are fixed to the inlet end of connecting tube 2 with AB glue. The two flat-headed needles are located on the left and right sides of the inlet end of the connecting tube, respectively, for introducing the intermediate phase fluid and the outer phase fluid. The outlet end of connecting tube 2 is sealed with AB glue, and each flat-headed needle is connected to the injection pump via a fitting.

[0062] In the following embodiments, a schematic diagram is shown of a rotating platform driving the collection container 4 to rotate around the axis of the collection container and applying ultraviolet light using an ultraviolet lamp 5. Figure 2 As shown. The specific operation is as follows: The collection container is placed on a rotating platform with its axis parallel to the horizontal plane. The rotating platform drives the collection container to rotate around its axis. When the core and shell of the double emulsion droplet are concentric, light is applied to the collection container while it continues to rotate, initiating photocrosslinking of the photocurable polymer monomers in the double emulsion droplet. The collection container is a cylindrical glass sample bottle.

[0063] In the following examples and comparative examples, the phosphorus-based flame retardant is model XF-960, purchased from Shanghai Xufan Chemical Co., Ltd.

[0064] Example 1

[0065] In this embodiment, a microfluidic controllable preparation method for fire extinguishing microcapsules is provided, the steps of which are as follows:

[0066] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0067] Perfluorohexanone was used as the internal phase fluid. A 1 wt% PVA aqueous solution was used as the external phase fluid.

[0068] The photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) and the phosphorus-based flame retardant were thoroughly mixed with tripropylene glycol diacrylate to obtain an intermediate phase fluid. In the intermediate phase fluid, the concentration of HMPP was 2 wt% and the concentration of the phosphorus-based flame retardant was 5 wt%.

[0069] (2) Preparation of double emulsion

[0070] The structure adopted is as follows Figure 1 The coaxial capillary microfluidic device shown was prepared.

[0071] The external phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump to wet the collection tube. Then, the intermediate phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump until a stable oil-in-water monoemulsion can be formed. Then, the internal phase fluid is injected into the injection tube of the coaxial capillary microfluidic device using a syringe pump to form a monodisperse oil-in-water (O1 / O2 / W) dual emulsion in the collection tube. The dual emulsion is collected in a collection container containing the external phase fluid.

[0072] In this step, the inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device is 80 μm, and the inner diameter of the receiving tube is 300 μm; the flow rate of the inner phase fluid is controlled at 25 μL / min, the flow rate of the intermediate phase fluid is 35 μL / min, and the flow rate of the outer phase fluid is 100 μL / min.

[0073] (3) Preparation of fire extinguishing microcapsules

[0074] When the total volume of the external phase fluid and the dual emulsion in the collection container reaches 95% of the collection container's volume, the collection container is sealed. The collection container is placed on a rotating platform with its axis parallel to the horizontal plane. The rotating platform drives the collection container to rotate around its axis for 10 minutes, controlling the rotation speed at 50 rpm. While maintaining the rotation, uniform ultraviolet light is applied from above the collection container to initiate photocrosslinking of tripropylene glycol diacrylate. After 8 minutes of ultraviolet light irradiation, the outer shell of the dual emulsion droplets solidifies. The resulting microcapsules are washed three times with pure water and dried to obtain fire extinguishing microcapsules.

[0075] In step (3) of this embodiment, an optical micrograph of the double emulsion droplet after rotating for 10 minutes is shown below. Figure 3 As shown. An optical micrograph of the fire extinguishing microcapsule prepared in step (3) of this embodiment is shown below. Figure 4 As shown, combined with Figure 4 Statistical analysis shows that the perfluorohexanone fire extinguishing microcapsules prepared in this embodiment have uniform size and good monodispersity. The outer diameter of the prepared fire extinguishing microcapsules is 285 μm, the coefficient of variation of the outer diameter is 0.5%, the diameter of the core is 225 μm, the thickness of the shell is 30 μm, the eccentricity between the shell and the core (core-shell structure eccentricity) is 0.05 (when the eccentricity is <0.1, the core is basically concentric, the shell thickness is uniform, and the structure is close to perfect), and the ratio of the shell thickness to the outer diameter of the fire extinguishing microcapsule is 0.105:1.

[0076] Comparative Example 1

[0077] The operation of this comparative example is basically the same as that of Example 1. The only difference is that in step (3), a rotating platform is not introduced to drive the collection container to rotate. After collecting the double emulsion in step (2), ultraviolet light is directly applied to solidify the shell of the double emulsion droplets while the collection container is stationary. The obtained microcapsules are washed with pure water 3 times and dried to obtain fire extinguishing microcapsules.

[0078] Optical micrographs of the fire extinguishing microcapsules prepared in this comparative example are shown below. Figure 5 As shown.

[0079] As can be seen from Example 1 and Comparative Example 1, before applying ultraviolet light to solidify the outer shell of the dual emulsion droplets, rotating the collection container around its axis using a rotating platform can significantly improve the concentricity between the core and the outer shell of the fire extinguishing microcapsule. Figure 5 It can be seen that the fire extinguishing microcapsules prepared in Comparative Example 1 exhibited a severe eccentricity problem, resulting in a very thin outer shell on the side where the core was offset; while the microcapsules prepared by Comparative Example 1... Figure 4 It can be seen that the core and shell of the fire extinguishing microcapsule prepared in Example 1 have a high degree of concentricity, and the shell thickness of the fire extinguishing microcapsule is uniform. However, the boiling point of perfluorohexanone is only 48°C. When the fire extinguishing microcapsule prepared in Comparative Example 1 is heated, the perfluorohexanone inside is easily vaporized due to the eccentricity problem and bursts out of the shell from the thinner part, thus failing to effectively encapsulate the fire extinguishing agent.

[0080] Comparative Example 2

[0081] The operation of this comparative example is basically the same as that of Example 1, except that the concentration of HMPP in the intermediate phase fluid prepared in step (1) is 3 wt%.

[0082] Comparative Example 3

[0083] The operation of this comparative example is basically the same as that of Example 1, except that the concentration of HMPP in the intermediate phase fluid prepared in step (1) is 0.3 wt%.

[0084] Figure 6 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 2. Figure 7 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 3. Examples 1 and Comparative Examples 2-3 were subjected to ultraviolet light for the same duration, and the... Figure 4 , 6 As shown in Figure 7, when the HMPP content in the mesophase fluid is 3 wt% and 0.3 wt%, the prepared fire extinguishing microcapsules also exhibit the problem of eccentricity, especially when the HMPP content in the mesophase fluid is 0.3 wt%, the eccentricity problem is more severe; however, when the HMPP content in the mesophase fluid is 2 wt%, fire extinguishing microcapsules with highly concentric cores and shells are prepared. This is mainly because the HMPP content in the mesophase fluid affects the photocrosslinking rate of tripropylene glycol diacrylate, and both excessively fast and slow photocrosslinking rates of tripropylene glycol diacrylate will affect the concentricity of the core and shell of the fire extinguishing microcapsule. Rotational synergistic UV curing can significantly improve the concentricity and wall thickness uniformity of the microcapsules, the key being that the photocrosslinking rate matches the rate of dynamic centering of the core of the dual emulsion droplets. When the photocrosslinking rate is too fast, the shell of the dual emulsion droplet solidifies before the dynamic correction of the core eccentricity is completed in the rotating field, easily causing core eccentricity and a decrease in sphericity. When the photocrosslinking rate is too slow, the shell remains in a flowing state for a long time, and the core is prone to displacement, rupture, or even failure to solidify under the disturbance of gravity, shear force, and rotating flow field, thus failing to maintain a stable concentric structure. Only at a suitable photocrosslinking rate can the dual emulsion droplet fully realize the centripetal movement and sphericity of the core in the rotating field and be solidified in the optimal structural state, thereby obtaining microcapsules with high concentricity and uniform wall thickness.

[0085] Example 2

[0086] In this embodiment, a microfluidic controllable preparation method for fire extinguishing microcapsules is provided, the steps of which are as follows:

[0087] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0088] Perfluorohexanone was used as the internal phase fluid. A 1 wt% PVA aqueous solution was used as the external phase fluid.

[0089] The photoinitiator HMPP and the phosphorus-based flame retardant were thoroughly mixed with propoxylated glycerol triacrylate to obtain an intermediate phase fluid; in the intermediate phase fluid, the concentration of HMPP was 2 wt% and the concentration of the phosphorus-based flame retardant was 5 wt%.

[0090] (2) Preparation of double emulsion

[0091] The structure adopted is as follows Figure 1 The coaxial capillary microfluidic device shown was prepared.

[0092] The external phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump to wet the collection tube. Then, the intermediate phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump until a stable oil-in-water monoemulsion can be formed. Then, the internal phase fluid is injected into the injection tube of the coaxial capillary microfluidic device using a syringe pump to form a monodisperse oil-in-water (O1 / O2 / W) dual emulsion in the collection tube. The dual emulsion is collected in a collection container containing the external phase fluid.

[0093] In this step, the inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device is 100 μm, and the inner diameter of the receiving tube is 300 μm; the flow rate of the inner phase fluid is controlled at 25 μL / min, the flow rate of the intermediate phase fluid is 35 μL / min, and the flow rate of the outer phase fluid is 100 μL / min.

[0094] (3) Preparation of fire extinguishing microcapsules

[0095] When the total volume of the external phase fluid and the dual emulsion in the collection container reaches 95% of the collection container's volume, the collection container is sealed. The collection container is placed on a rotating platform with its axis parallel to the horizontal plane. The rotating platform drives the collection container to rotate around its axis for 10 minutes, controlling the rotation speed at 50 rpm. While maintaining the rotation, uniform ultraviolet light is applied from above the collection container to initiate photocrosslinking of propoxylated glycerol triacrylate. After 8 minutes of ultraviolet irradiation, the outer shell of the dual emulsion droplets solidifies. The resulting microcapsules are washed three times with pure water and dried to obtain fire extinguishing microcapsules.

[0096] In step (3) of this embodiment, an optical micrograph of the double emulsion droplet after rotating for 10 minutes is shown below. Figure 8 As shown. An optical micrograph of the fire extinguishing microcapsule prepared in step (3) of this embodiment is shown below. Figure 9 As shown, combined with Figure 9 Statistical analysis shows that the perfluorohexanone fire extinguishing microcapsules prepared in this embodiment have uniform size and good monodispersity. The outer diameter of the prepared fire extinguishing microcapsules is 300 μm, the coefficient of variation of the outer diameter is 0.7%, the diameter of the core is 245 μm, the thickness of the shell is 27.5 μm, the eccentricity between the shell and the core (core-shell structure eccentricity) is 0.04, and the ratio of the shell thickness to the outer diameter of the fire extinguishing microcapsule is 0.092:1.

[0097] Comparative Example 4

[0098] The operation of this comparative example is basically the same as that of Example 2. The only difference is that in step (3), a rotating platform is not introduced to drive the collection container to rotate. After collecting the double emulsion in step (2), ultraviolet light is directly applied to solidify the shell of the double emulsion droplets while the collection container is stationary. The obtained microcapsules are washed with pure water 3 times and dried to obtain fire extinguishing microcapsules.

[0099] Optical micrographs of the fire extinguishing microcapsules prepared in this comparative example are shown below. Figure 10 As shown.

[0100] As can be seen from Example 2 and Comparative Example 4, before applying ultraviolet light to solidify the outer shell of the dual emulsion droplets, rotating the collection container around its axis using a rotating platform can significantly improve the concentricity between the core and the outer shell of the fire extinguishing microcapsule. Figure 10 It can be seen that the fire extinguishing microcapsules prepared in Comparative Example 4 exhibited an eccentricity problem, while those prepared by... Figure 9 It can be seen that the core and shell of the fire extinguishing microcapsule prepared in Example 2 have a high degree of concentricity. However, the boiling point of perfluorohexanone is only 48°C. When the fire extinguishing microcapsule prepared in Comparative Example 4 is heated, the perfluorohexanone inside is easily vaporized due to the eccentricity problem and bursts out of the shell from the thinner part, thus failing to effectively encapsulate the fire extinguishing agent.

[0101] Comparative Example 5

[0102] The operation of this comparative example is basically the same as that of Example 2, except that the concentration of HMPP in the intermediate phase fluid prepared in step (1) is 3 wt%.

[0103] Comparative Example 6

[0104] The operation of this comparative example is basically the same as that of Example 2, except that the concentration of HMPP in the intermediate phase fluid prepared in step (1) is 0.3 wt%.

[0105] Figure 11 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 5. Figure 12 This is an optical micrograph of the fire extinguishing microcapsules prepared in Comparative Example 6. In Example 2, the ultraviolet light irradiation time applied to Comparative Examples 5 and 6 was the same, and... Figure 9 , 11As shown in section 12, when the HMPP content in the mesophase fluid is 3 wt% and 0.3 wt%, the prepared fire extinguishing microcapsules also suffer from eccentricity and cannot successfully encapsulate perfluorohexanone. However, when the HMPP content in the mesophase fluid is 2 wt%, fire extinguishing microcapsules with highly concentric cores and shells are obtained. This is mainly because the HMPP content in the mesophase fluid affects the photocrosslinking rate of propoxylated glycerol triacrylate, and both excessively fast and slow photocrosslinking rates of propoxylated glycerol triacrylate affect the concentricity of the core and shell of the fire extinguishing microcapsule. This indicates that the method described in this invention requires an appropriate photocrosslinking rate of the photocrosslinking monomer and controlled rotation of the collection container around its axis at an appropriate speed to achieve the effect of improving the concentricity of the core and shell of the fire extinguishing microcapsule.

[0106] Example 3

[0107] In this embodiment, a microfluidic controllable preparation method for fire extinguishing microcapsules is provided, the steps of which are as follows:

[0108] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0109] Perfluorohexanone was used as the internal phase fluid. A 5 wt% PVA aqueous solution was used as the external phase fluid.

[0110] The photoinitiator HMPP and the phosphorus-based flame retardant were thoroughly mixed with propoxylated glycerol triacrylate to obtain an intermediate phase fluid. In the intermediate phase fluid, the concentration of HMPP was 2.5 wt% and the concentration of the phosphorus-based flame retardant was 10 wt%.

[0111] (2) Preparation of double emulsion

[0112] The structure adopted is as follows Figure 1 The coaxial capillary microfluidic device shown was prepared.

[0113] The external phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump to wet the collection tube. Then, the intermediate phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump until a stable oil-in-water monoemulsion can be formed. Then, the internal phase fluid is injected into the injection tube of the coaxial capillary microfluidic device using a syringe pump to form a monodisperse oil-in-water (O1 / O2 / W) dual emulsion in the collection tube. The dual emulsion is collected in a collection container containing the external phase fluid.

[0114] In this step, the inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device is 100 μm, and the inner diameter of the receiving tube is 300 μm; the flow rate of the inner phase fluid is controlled at 20 μL / min, the flow rate of the intermediate phase fluid is 40 μL / min, and the flow rate of the outer phase fluid is 80 μL / min.

[0115] (3) Preparation of fire extinguishing microcapsules

[0116] When the total volume of the external phase fluid and the dual emulsion in the collection container reaches 85% of the collection container's volume, the collection container is sealed. The collection container is placed on a rotating platform with its axis parallel to the horizontal plane. The rotating platform drives the collection container to rotate around its axis for 15 minutes, controlling the rotation speed at 15 rpm. While maintaining the rotation, uniform ultraviolet light is applied from above the collection container to initiate photocrosslinking of propoxylated glycerol triacrylate. After 5 minutes of ultraviolet irradiation, the outer shell of the dual emulsion droplets solidifies. The resulting microcapsules are washed three times with pure water and dried to obtain fire extinguishing microcapsules.

[0117] Example 4

[0118] In this embodiment, a microfluidic controllable preparation method for fire extinguishing microcapsules is provided, the steps of which are as follows:

[0119] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0120] Perfluorohexanone was used as the internal phase fluid. A PVA aqueous solution with a PVA concentration of 2 wt% was used as the external phase fluid.

[0121] The photoinitiator HMPP and the phosphorus-based flame retardant were thoroughly mixed with propoxylated glycerol triacrylate to obtain an intermediate phase fluid. In the intermediate phase fluid, the concentration of HMPP was 0.5 wt% and the concentration of the phosphorus-based flame retardant was 5 wt%.

[0122] (2) Preparation of double emulsion

[0123] The structure adopted is as follows Figure 1 The coaxial capillary microfluidic device shown was prepared.

[0124] The external phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump to wet the collection tube. Then, the intermediate phase fluid is injected into the collection tube of the coaxial capillary microfluidic device using a syringe pump until a stable oil-in-water monoemulsion can be formed. Then, the internal phase fluid is injected into the injection tube of the coaxial capillary microfluidic device using a syringe pump to form a monodisperse oil-in-water (O1 / O2 / W) dual emulsion in the collection tube. The dual emulsion is collected in a collection container containing the external phase fluid.

[0125] In this step, the inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device is 100 μm, and the inner diameter of the receiving tube is 700 μm; the flow rate of the inner phase fluid is controlled at 140 μL / min, the flow rate of the intermediate phase fluid is 230 μL / min, and the flow rate of the outer phase fluid is 1500 μL / min.

[0126] (3) Preparation of fire extinguishing microcapsules

[0127] When the total volume of the external phase fluid and the dual emulsion in the collection container reaches 90% of the collection container's volume, the collection container is sealed. The collection container is placed on a rotating platform with its axis parallel to the horizontal plane. The rotating platform drives the collection container to rotate around its axis for 5 minutes, controlling the rotation speed of the collection container at 100 rpm. While maintaining rotation, uniform ultraviolet light is applied from above the collection container to initiate photocrosslinking of propoxylated glycerol triacrylate. After 10 minutes of ultraviolet light irradiation, the outer shell of the dual emulsion droplets solidifies. The resulting microcapsules are washed three times with pure water and dried to obtain fire extinguishing microcapsules.

[0128] Example 5

[0129] In this embodiment, three fire extinguishing microcapsules with different shell materials were prepared, and their mechanical properties were investigated.

[0130] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0131] Perfluorohexanone was used as the internal phase fluid. A 1 wt% PVA aqueous solution was used as the external phase fluid.

[0132] The photoinitiator HMPP and the phosphorus-based flame retardant were thoroughly mixed with the photocurable polymer monomer to obtain an intermediate phase fluid. In the intermediate phase fluid, the concentration of HMPP was 2 wt% and the concentration of the phosphorus-based flame retardant was 5 wt%. In this step, three different intermediate phase fluids were prepared by using tripropylene glycol diacrylate, propoxylated glycerol triacrylate, or trimethylolpropane triacrylate as photocurable polymer monomers, respectively.

[0133] (2) Preparation of double emulsion

[0134] The same procedure as step (2) of Example 1 was followed to prepare three different dual emulsions of photocurable polymer monomers. The only difference was that in this step, the inner diameter of the conical opening of the injection tube of the coaxial capillary microfluidic device was 100 μm and the inner diameter of the receiving tube was 300 μm. The flow rate of the inner phase fluid was controlled to be 25 μL / min, the flow rate of the intermediate phase fluid was 25 μL / min, and the flow rate of the outer phase fluid was 120 μL / min.

[0135] (3) Preparation of fire extinguishing microcapsules

[0136] Following the same procedure as step (3) in Example 1, three types of fire extinguishing microcapsules with different shell materials were obtained.

[0137] (4) Mechanical property testing

[0138] Three types of fire extinguishing microcapsules with different outer shell materials were placed in test chambers and tested on a mechanical strength tester using a 250g sensor and an 800 μm probe. The force-displacement curves of the fire extinguishing microcapsules were obtained, as shown below. Figure 13 As shown in the figure, TPGDA represents fire extinguishing microcapsules prepared using tripropylene glycol diacrylate as a photocurable polymer monomer, GPTA represents fire extinguishing microcapsules prepared using propoxylated glycerol triacrylate as a photocurable polymer monomer, and TMPTA represents fire extinguishing microcapsules prepared using trimethylolpropane triacrylate as a photocurable polymer monomer. Figure 13 It can be seen that when trimethylolpropane triacrylate is used as the photocurable polymer monomer, the mechanical properties of the fire extinguishing microcapsule are the best, followed by propoxylated glycerol triacrylate, and lastly tripropylene glycol diacrylate. This shows that under the same preparation conditions, the mechanical properties of the fire extinguishing microcapsule can be controlled by changing the type of photocurable polymer monomer to regulate the shell material.

[0139] Example 6

[0140] In this embodiment, fire extinguishing microcapsules were prepared under different conditions, and their thermal response temperatures were investigated.

[0141] (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid

[0142] Perfluorohexanone was used as the internal phase fluid. A 1 wt% PVA aqueous solution was used as the external phase fluid.

[0143] The photoinitiator HMPP and the phosphorus-based flame retardant were thoroughly mixed with the photocurable polymer monomer to obtain an intermediate phase fluid. In the intermediate phase fluid, the concentration of HMPP was 2 wt% and the concentration of the phosphorus-based flame retardant was 5 wt%. In this step, three different intermediate phase fluids were prepared by using tripropylene glycol diacrylate, propoxylated glycerol triacrylate, or trimethylolpropane triacrylate as photocurable polymer monomers, respectively.

[0144] (2) Preparation of double emulsion

[0145] This step sets up four sets of experiments. The experimental operation is basically the same as step (2) of Example 1, with the only difference being:

[0146] Experiment 1: The intermediate phase fluid used was prepared with tripropylene glycol diacrylate as the photocurable polymer monomer. The inner diameter of the conical nozzle of the injection tube of the coaxial capillary microfluidic device was 100 μm, and the inner diameter of the receiving tube was 300 μm. The flow rate of the inner phase fluid was controlled at 25 μL / min, the flow rate of the intermediate phase fluid was 25 μL / min, and the flow rate of the outer phase fluid was 120 μL / min.

[0147] Experiment 2: The intermediate phase fluid used was prepared with tripropylene glycol diacrylate as the photocurable polymer monomer. The inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device was 100 μm, the inner diameter of the receiving tube was 700 μm, and the flow rate of the inner phase fluid was controlled at 80 μL / min, the flow rate of the intermediate phase fluid was 120 μL / min, and the flow rate of the outer phase fluid was 800 μL / min.

[0148] Experiment 3: The intermediate phase fluid used was prepared with propoxylated glycerol triacrylate as the photocurable polymer monomer. The inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device was 100 μm, the inner diameter of the receiving tube was 700 μm, and the flow rate of the inner phase fluid was controlled at 70 μL / min, the flow rate of the intermediate phase fluid was 230 μL / min, and the flow rate of the outer phase fluid was 1200 μL / min.

[0149] Experiment 4: The intermediate phase fluid used was prepared with trimethylolpropane triacrylate as the photocurable polymer monomer. The inner diameter of the conical inlet of the injection tube of the coaxial capillary microfluidic device was 100 μm, the inner diameter of the receiving tube was 700 μm, and the flow rate of the inner phase fluid was controlled at 70 μL / min, the flow rate of the intermediate phase fluid was 230 μL / min, and the flow rate of the outer phase fluid was 1200 μL / min.

[0150] (3) Preparation of fire extinguishing microcapsules

[0151] The same procedure as step (3) in Example 1 was followed to obtain four types of fire extinguishing microcapsules. The fire extinguishing microcapsules prepared based on the dual emulsions prepared in Experiments 1 to 4 were respectively named TPGDA1, TPGDA2, GPTA and TMPTA.

[0152] (4) Thermal response temperature test

[0153] Thermogravimetric analysis was performed on 5-10 mg of the fire extinguishing microcapsules (TPGDA1, TPGDA2, GPTA, TMPTA) prepared in Example 3, and the results are as follows. Figures 14-15 As shown.

[0154] Depend on Figure 14It is known that, under the same shell material conditions, microfluidic conditions affect the thermal response temperature of the fire extinguishing microcapsule. The fire extinguishing microcapsule TPGDA1, prepared under conditions of smaller channel size and lower fluid flow rate, has a lower thermal response temperature, around 80 °C. Conversely, the fire extinguishing microcapsule TPGDA2, prepared under conditions of larger channel size and higher fluid flow rate, has a higher thermal response temperature, around 180 °C. This is mainly due to the increased particle size and shell thickness of the fire extinguishing microcapsule. This indicates that, using the method of the present invention, under the same shell material conditions, the size and shell thickness of the fire extinguishing microcapsule can be controlled by adjusting the microfluidic conditions, thereby controlling its thermal response temperature.

[0155] Depend on Figure 15 It is known that, under the same microfluidic conditions, the shell material affects the thermal response temperature of the fire extinguishing microcapsule. When trimethylolpropane triacrylate is used as the photocurable polymer monomer, the thermal response temperature of the prepared fire extinguishing microcapsule is approximately 250 °C. When propoxylated glycerol triacrylate is used as the photocurable polymer monomer, the thermal response temperature of the prepared fire extinguishing microcapsule is approximately 200 °C. This indicates that, using the method of the present invention, under the same microfluidic conditions, the thermal response temperature of the fire extinguishing microcapsule can be controlled by adjusting the type of photocurable polymer monomer.

[0156] As can be seen from Examples 5 and 6, the method of the present invention can control the shell material, shell thickness, and particle size of the fire extinguishing microcapsules by adjusting microfluidic conditions and shell material, thereby achieving precise control of mechanical properties and thermal response temperature. In practical applications, the controllable adjustment of the mechanical properties and thermal response temperature of the fire extinguishing microcapsules is beneficial to the controllable release of the extinguishing agent within the microcapsules, thereby improving the stability of the fire extinguishing microcapsules during storage, transportation, and in actual environments, and preventing premature leakage or failure of the extinguishing agent. Through the synergistic optimization of mechanical properties and thermal response behavior, the fire extinguishing microcapsules can achieve precise triggering and efficient flame suppression during a fire, while simultaneously meeting the comprehensive requirements of engineering applications for material strength, durability, and environmental adaptability.

Claims

1. A microfluidic controllable preparation method for fire extinguishing microcapsules, characterized in that, Includes the following steps: (1) Preparation of internal phase fluid, intermediate phase fluid and external phase fluid Using liquid fluorine-containing fire extinguishing agents as the internal phase fluid; A photoinitiator is fully dispersed or dissolved in a liquid photocurable polymer monomer to obtain an intermediate phase fluid, wherein the concentration of the photoinitiator in the intermediate phase fluid is 0.5 wt% to 2.5 wt%; a surfactant is dissolved in water to obtain an external phase fluid, wherein the concentration of the surfactant in the external phase fluid is 1 wt% to 5 wt%; the internal phase fluid and the intermediate phase fluid are immiscible. (2) Preparation of double emulsion The inner phase fluid is introduced into the injection tube of the coaxial capillary microfluidic device, and the intermediate phase fluid and the outer phase fluid are introduced into the collection tube of the coaxial capillary microfluidic device to form a monodisperse oil-in-water double emulsion in the collection tube. The double emulsion is collected in a collection container containing the outer phase fluid. The main body of the collection container is cylindrical and made of a light-transmitting material. (3) Preparation of fire extinguishing microcapsules Seal the collection container, keep its axis horizontal, and rotate it around its axis for 1-15 minutes. While keeping the container rotating, apply light to it to induce photo-crosslinking of the photocurable polymer monomers in the double emulsion droplets until the outer shell of the double emulsion droplets is cured. Then clean and dry to obtain the fire extinguishing microcapsules.

2. The microfluidic controllable preparation method of the fire extinguishing microcapsule according to claim 1, characterized in that, In step (3), the rotation speed of the collection container around its axis is controlled to be 15~100 rpm.

3. The microfluidic controllable preparation method of the fire extinguishing microcapsule according to claim 1, characterized in that, In step (3), when the total volume of the external phase fluid and the dual emulsion in the collection container reaches 85% to 100% of the volume of the collection container, the collection container is sealed.

4. The microfluidic controllable preparation method of the fire extinguishing microcapsule according to any one of claims 1 to 3, characterized in that, The illumination time in step (3) is 1~10 min.

5. A microfluidic controllable preparation method of the fire extinguishing microcapsule according to any one of claims 1 to 3, characterized in that, The photocurable polymer monomer is an acrylate-based photocurable polymer monomer.

6. The microfluidic controllable preparation method of the fire extinguishing microcapsule according to any one of claims 1 to 3, characterized in that, The mesophase fluid also contains flame retardant materials, and the content of flame retardant materials in the mesophase fluid is 5 wt% to 15 wt%.

7. A microfluidic controllable preparation method of the fire extinguishing microcapsule according to any one of claims 1 to 3, characterized in that, In step (2), the flow rate ratio of the inner phase fluid, the intermediate phase fluid and the outer phase fluid is controlled to be (20~140):(25~230):(80~1500).

8. A fire extinguishing microcapsule prepared by the method of any one of claims 1 to 7, the fire extinguishing microcapsule being composed of an outer shell and a liquid fluorine-containing fire extinguishing agent encapsulated within the outer shell, wherein the outer shell of the fire extinguishing microcapsule has a uniform thickness and the eccentricity between the outer shell and the inner core of the fire extinguishing microcapsule is less than 0.

1.

9. The fire extinguishing microcapsule according to claim 8, characterized in that, The outer shell of the fire extinguishing microcapsule has a thickness of 1~100 mm, and the ratio of the outer shell thickness to the outer diameter of the fire extinguishing microcapsule is (0.01~0.6):

1.

10. The fire extinguishing microcapsule according to claim 8 or 9, characterized in that, The thermal response temperature of the fire extinguishing microcapsule is 80~250℃.

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