Safe and environment-friendly microcapsule energetic material and preparation method thereof

Abstract

The invention relates to a safe and environment-friendly microcapsule energetic material and a preparation method thereof, and belongs to the technical field of energetic materials. According to the energetic material, a polymer fluorine polymer / active metal powder mixture serves as a core material and is coated with a polymer wall material through a microencapsulation packaging technology, and the surface of a microcapsule is coated with a nano flame-retardant coating, so that the energetic material with the characteristics of impact resistance, heat resistance, slight smoke, low mechanical sensitivity, high safety and environmental protection is obtained.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials technology, specifically relating to safe and environmentally friendly microcapsule energetic materials and their preparation methods. Background Technology

[0002] In the industrial production of energetic materials, traditional materials such as black powder mainly consist of potassium nitrate (oxidant), charcoal (reducing agent), and sulfur (flammable agent). This formula is inexpensive, safe to operate, and easy to manufacture. However, from an environmental perspective, black powder produces a large amount of black smoke when burning, affecting the performance of fireworks. Furthermore, incomplete combustion leaves behind a large amount of carbon, sulfur, potassium oxides, and solid residue, severely polluting the environment. From a safety perspective, black powder has high mechanical sensitivity and is easily ignited or exploded under strong impact or friction. Therefore, it has low safety during production and transportation, posing a significant danger to human life and property.

[0003] In recent years, research on novel energetic materials that improve the environmental protection and safety performance of energetic materials by constructing polymer materials and active metal systems has become a hot topic in the industry. Requirements for high reliability, long-term stability, and anti-aging performance under harsh conditions are constantly increasing. Based on these issues and practical needs, the research and development of safe, reliable, and efficient environmentally friendly energetic materials and their preparation methods has become an urgent problem to be solved by the industry. Summary of the Invention

[0004] To address the aforementioned issues, this invention aims to overcome the shortcomings of existing energetic materials in terms of safety and environmental adaptability. By employing microencapsulation technology, a mixture of polymeric fluorinated polymers and active metal powders is used as the core material, encapsulated with a polymeric wall material, and coated with a nano-flame-retardant coating on the surface of the microcapsules. This results in an energetic material with impact resistance, heat resistance, low smoke, low mechanical sensitivity, high safety, and environmental friendliness.

[0005] To achieve the above-mentioned technical effects, the present invention provides a method for preparing a safe and environmentally friendly microcapsule energetic material, comprising the following steps: S1: preparing surface-modified active metal powder; S2: coating the active metal powder obtained in S1 with a binder and mixing it with a polymeric fluorinated polymer to obtain a polymeric fluorinated polymer / active metal powder core mixed slurry; S3: further emulsifying the slurry obtained in S3 in an aqueous phase containing a stabilizer, and obtaining a uniform emulsion suspension with no obvious particle sedimentation by ultrasonic dispersion treatment, heating under an inert gas atmosphere, and uniformly adding synthetic polymers to the emulsion suspension. The monomers of the coating material are used to initiate and maintain the polymerization reaction. After cooling, filtration, washing, and drying, polymer fluorinated polymer / active metal powder microcapsules with preliminary polymer coating material are obtained; S4: The polymer fluorinated polymer / modified active metal powder microcapsules obtained in S3 are coated to obtain polymer fluorinated polymer / active metal powder microcapsule energetic material particles with a continuous and dense nanocomposite flame retardant layer on the surface; S5: The polymer fluorinated polymer / active metal powder microcapsule energetic material particles obtained in S4 are screened and packaged to obtain safe and environmentally friendly microcapsule energetic material.

[0006] Optionally, S1 specifically includes: S11: adding the silane coupling agent to an organic solvent and stirring until homogeneous to obtain a mixed solution; S12: under an inert gas atmosphere, dispersing the active metal powder into the solution obtained in S11, soaking for a certain period of time, and then filtering and drying to obtain surface-modified active metal powder.

[0007] Optionally, the silane coupling agent in S11 is one or more of aminosilane, epoxysilane, methacryloxysilane, mercaptosilane, vinylsilane, etc.; the organic solvent in S11 is one or more of ethyl acetate, acetone, toluene, xylene, n-hexane, cyclohexane, chloroform, dichloromethane, tetrahydrofuran, etc.; the stirring time in S11 is 1~6h, and the stirring rate is 100~200rpm; the inert gas in S12 is composed of nitrogen, argon, or helium, etc.; the active metal powder in S12 is one or more of aluminum powder, magnesium powder, boron powder, zirconium powder, zinc powder, titanium powder, silicon powder, tin powder, etc.; and the soaking time in S12 is 6~12h.

[0008] Optionally, S2 specifically includes: S21: adding a binder to an organic solvent and stirring until completely dissolved; S22: adding the surface-modified active metal powder obtained in S1 to the binder-containing solution obtained in S21, stirring for a certain time to obtain a dispersion containing active metal powder coated with binder; S23: adding a polymeric fluorinated polymer to the dispersion, and continuing to stir for a certain time to obtain a polymeric fluorinated polymer / active metal powder core mixed slurry.

[0009] Optionally, the organic solvent in S21 is one or more of ethyl acetate, acetone, toluene, xylene, n-hexane, cyclohexane, chloroform, dichloromethane, tetrahydrofuran, etc.; the stirring time in S21 is 2-4 hours, and the stirring speed is 200-400 rpm; the binder in S21 is one or more of nitrocellulose, ethyl cellulose, cellulose acetate, polymethyl methacrylate (PMMA), polyvinyl acetate, epoxy resin, phenolic resin, fluororubber, hydroxyl-terminated polybutadiene, etc.; the stirring time in S22 is 1-3 hours, and the stirring speed is 300-500 rpm; the high molecular weight fluorinated polymer in S23 is any one or more of perfluoropolyether, polyvinylidene fluoride, polyfluoroolefin, polyfluoroalkane, and perfluoroethylene; the stirring time in S23 is 2-4 hours, and the stirring speed is 400-600 rpm.

[0010] Optionally, in step S3, the stabilizer is one or more of water-soluble polymeric emulsifiers with similar functions, such as polyvinyl alcohol, hydroxyethyl cellulose, sodium carboxymethyl cellulose, gelatin, gum arabic, and polyvinylpyrrolidone; the ultrasonic dispersion time is 0.5-1 h, the temperature rise is 40-80 °C, and the drying time is 4-6 h; the inert gas is one of nitrogen, argon, or helium; the temperature rise range is from room temperature to 40-80 °C, and the heating rate is 1-5 °C / min; the synthetic polymeric coating material is selected from any one or more of methyl methacrylate (MMA), styrene, acrylonitrile, ε-caprolactam, undecylactam, and acrylamide; the polymerization reaction is maintained for 4-8 h, and the drying time is 4-6 h.

[0011] Optionally, S4 specifically includes: S41: adding nano flame retardant material and water-based wetting agent to deionized water or ethanol in a certain proportion, and performing ultrasonic dispersion treatment to prepare nano flame retardant coating liquid; S42: using the nano flame retardant coating liquid obtained in S41 to spray or dip the polymer fluorinated polymer / active metal powder microcapsules initially coated with polymer coating material obtained in S3 at least sequentially to obtain polymer fluorinated polymer / active metal powder microcapsule energetic material particles with a continuous and dense nanocomposite flame retardant layer formed on the surface.

[0012] Optionally, the nano-flame retardant material in S41 is any one of nano-alumina, nano-alumina hydroxide, nano-silica, or nano-phosphorus flame retardants, or a combination of multiple thereof; the aqueous wetting agent in S41 is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium polyacrylate, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, sodium polyacrylate dispersant, etc.; the ratio of nano-flame retardant material to aqueous wetting agent in S41 is 1:0.01~1:0.2; the ultrasonic dispersion treatment time in S41 is 0.5~2h; the number of spraying or dipping treatments in S42 is 1-2 times, and the spraying or dipping rate is 0.4-0.8mL / min.

[0013] Optionally, in step S5: the sieve used for sieving is 80-120 mesh; the particle size obtained by sieving is 150-180 μm, and the particles are vacuum dried after sieving, wherein the vacuum drying pressure is <0.1 Pa, the temperature is 50-60℃, and the time is 4-6 h; the packaging uses a protective bag under inert gas protection.

[0014] In another aspect, the present invention provides a safe and environmentally friendly microcapsule energetic material, prepared by the aforementioned preparation method, wherein the safe and environmentally friendly microcapsule energetic material is used in the field of environmentally friendly energetic materials.

[0015] The beneficial effects of this invention are as follows: (1) According to the microcapsule coating technology provided by the present invention, the polymerization reaction of polymer material coating is carried out on the outer surface of the core formed by the mixture of polymer fluorinated polymer / active metal powder, which can significantly reduce the probability of external mechanical, friction or thermal stimulation being transmitted to the core, while achieving uniform dispersion and stable storage of microcapsule particles.

[0016] (2) Introduce a nano flame-retardant coating on the surface of the microcapsule structure that forms a polymer material coating to ensure the formation of a heat-insulating carbonized layer or the release of inert gas under high temperature conditions, thereby enhancing the heat resistance and insulation performance and further improving the safe storage and use performance of energetic materials.

[0017] (3) In the overall preparation process, chemical modification, coating, powder mixing, emulsion polymerization microcapsule coating and nano flame retardant coating were used in succession. The process relationship between the preceding and following processes was standardized. The overall process conditions were relatively mild and the raw materials were easy to obtain, which well met the needs of industrial production.

[0018] (4) Compared with traditional black powder, the prepared energetic material has advantages such as being sulfur-free and nitrogen-free, environmentally friendly and producing little smoke, having low mechanical sensitivity, high safety, heat resistance and insulation, controllable release, and stable storage.

[0019] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0020] The accompanying drawings, which are provided to further illustrate the invention and form part of this application, do not constitute a limitation thereof; it should be noted that the drawings themselves are not within the scope of protection of this patent.

[0021] Figure 1 This is a flowchart illustrating the preparation method of the safe and environmentally friendly microcapsule energetic material of this invention. Figure 2 This is a flowchart illustrating the preparation of the environmentally friendly microcapsule energetic material in this invention. Figure 3 This is a diagram showing the combustion effect of the safe and environmentally friendly microcapsule energetic material obtained in Example 1 of the present invention; Figure 4 This is a diagram showing the combustion effect of the energetic material obtained in Comparative Example 2 of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention. It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only structures and / or processing steps closely related to the solutions according to the invention are shown in the accompanying drawings, while other details not closely related to the invention are omitted.

[0023] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0024] The embodiments of the present invention will now be described in detail and clearly with reference to the accompanying drawings.

[0025] The first aspect of the embodiments of the present invention, as follows: Figure 1As shown, a method for preparing a safe and environmentally friendly microcapsule energetic material is provided, comprising the following steps: S1: preparing surface-modified active metal powder; S2: coating the active metal powder of S1 with a binder and mixing it with a polymeric fluorinated polymer to obtain a polymeric fluorinated polymer / active metal powder core mixed slurry; S3: further emulsifying the slurry obtained in S3 in an aqueous phase containing a stabilizer, and obtaining a uniform emulsion suspension with no obvious particle sedimentation by ultrasonic dispersion treatment; heating under an inert gas atmosphere, uniformly adding monomers of the synthesized polymeric coating material to the emulsion suspension and initiating... The polymerization reaction is carried out and maintained. After cooling, filtration, washing and drying, polymer fluorinated polymer / active metal powder microcapsules with preliminary polymer coating material are obtained; S4: The polymer fluorinated polymer / modified active metal powder microcapsules obtained in S3 are coated to obtain polymer fluorinated polymer / active metal powder microcapsule energetic material particles with a continuous and dense nanocomposite flame retardant layer on the surface; S5: The polymer fluorinated polymer / active metal powder microcapsule energetic material particles obtained in S4 are screened and packaged to obtain safe and environmentally friendly microcapsule energetic material.

[0026] Optionally, S1 specifically includes: S11: adding the silane coupling agent to an organic solvent and stirring until homogeneous to obtain a mixed solution; S12: under an inert gas atmosphere, dispersing the active metal powder into the solution obtained in S11, soaking for a certain period of time, and then filtering and drying to obtain surface-modified active metal powder.

[0027] Optionally, the silane coupling agent in S11 is one or more of aminosilane, epoxysilane, methacryloxysilane, mercaptosilane, vinylsilane, etc.; the organic solvent in S11 is one or more of ethyl acetate, acetone, toluene, xylene, n-hexane, cyclohexane, chloroform, dichloromethane, tetrahydrofuran, etc.; the stirring time in S11 is 1~6h, and the stirring rate is 100~200rpm; the inert gas in S12 is composed of nitrogen, argon, or helium, etc.; the active metal powder in S12 is one or more of aluminum powder, magnesium powder, boron powder, zirconium powder, zinc powder, titanium powder, silicon powder, tin powder, etc.; and the soaking time in S12 is 6~12h.

[0028] Optionally, S2 specifically includes: S21: adding a binder to an organic solvent and stirring until completely dissolved; S22: adding the surface-modified active metal powder obtained in S1 to the binder-containing solution obtained in S21, stirring for a certain time to obtain a dispersion containing active metal powder coated with binder; S23: adding a polymeric fluorinated polymer to the dispersion, and continuing to stir for a certain time to obtain a polymeric fluorinated polymer / active metal powder core mixed slurry.

[0029] Optionally, the organic solvent in S21 is one or more of ethyl acetate, acetone, toluene, xylene, n-hexane, cyclohexane, chloroform, dichloromethane, tetrahydrofuran, etc.; the stirring time in S21 is 2-4 hours, and the stirring speed is 200-400 rpm; the binder in S21 is one or more of nitrocellulose, ethyl cellulose, cellulose acetate, polymethyl methacrylate (PMMA), polyvinyl acetate, epoxy resin, phenolic resin, fluororubber, hydroxyl-terminated polybutadiene, etc.; the stirring time in S22 is 1-3 hours, and the stirring speed is 300-500 rpm; the high molecular weight fluorinated polymer in S23 is any one or more of perfluoropolyether, polyvinylidene fluoride, polyfluoroolefin, polyfluoroalkane, and perfluoroethylene; the stirring time in S23 is 2-4 hours, and the stirring speed is 400-600 rpm.

[0030] Optionally, in S3, the stabilizer is one or more of the following water-soluble polymeric emulsifiers with similar functions: polyvinyl alcohol, hydroxyethyl cellulose, sodium carboxymethyl cellulose, gelatin, gum arabic, polyvinylpyrrolidone, etc.; the ultrasonic dispersion time is 0.5-1 h, the temperature rise is 40-80℃, and the drying time is 4-6 h; the inert gas is one of nitrogen, argon, or helium; the temperature rise range is from room temperature to 40-80℃, and the heating rate is 1-5°C / min; the synthesized polymeric coating material is any one or more selected from methyl methacrylate (MMA), styrene, acrylonitrile, ε-caprolactam, undecylactam, acrylamide, etc.; the polymerization reaction time is 4-8 h, and the drying time is 4-6 h.

[0031] Optionally, S4 specifically includes: S41: adding nano flame retardant material and water-based wetting agent to deionized water or ethanol in a certain proportion, and performing ultrasonic dispersion treatment to prepare nano flame retardant coating liquid; S42: using the nano flame retardant coating liquid obtained in S41 to spray or dip-coat the polymer fluorinated polymer / active metal powder microcapsules initially coated with polymer coating material obtained in S3 to obtain polymer fluorinated polymer / active metal powder microcapsule energetic material particles with a continuous and dense nanocomposite flame retardant layer formed on the surface.

[0032] Optionally, the nano-flame retardant material in S41 is any one of nano-alumina, nano-alumina hydroxide, nano-silica, or nano-phosphorus flame retardants, or a combination of multiple thereof; the water-based wetting agent in S41 is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium polyacrylate, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, sodium polyacrylate dispersant, etc.; the ratio of nano-flame retardant material to water-based wetting agent in S41 is 1:0.01 to 1:0.2; the ultrasonic dispersion treatment time in S41 is 0.5 to 2 hours; the number of spraying or dipping treatments in S42 is 1 to 2 times, and the spraying or dipping rate is 0.4 to 0.8 mL / min.

[0033] Optionally, in S5: the sieve used for sieving is 80-120 mesh; the particle size obtained by sieving is 150-180μm, and the particles are vacuum dried after sieving, wherein the vacuum drying pressure is <0.1Pa, the temperature is 50-60℃, and the time is 4-6h; the packaging uses a protective bag under inert gas protection.

[0034] In another aspect, this invention provides a safe and environmentally friendly microcapsule energetic material, prepared by a preparation method, which is used in the field of environmentally friendly energetic materials.

[0035] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0036] Example 1 Appendix Figure 2 The document illustrates the preparation process of the safe and environmentally friendly microcapsule energetic material in Embodiment 1 of the present invention. Unless otherwise specified, all proportions in the embodiments of the present invention are expressed in units of mass. The specific steps are as follows: (1) Modification of metal powder Surface modification: 1 part of aminosilane was weighed and added to ethyl acetate, stirred for 2 hours at a stirring speed of 150 rpm, and 32 parts of aluminum powder were dispersed in the solution under nitrogen protection, soaked for 6 hours, filtered and dried to obtain modified metal powder; wherein, the active metal powder is spherical with a particle size of 10 μm; (2) Preparation of core mixed slurry Coating: Weigh 2 parts of nitrocellulose and add it to ethyl acetate. Stir for 3 hours at a stirring speed of 300 rpm until completely dissolved. Disperse the above 32 parts of modified metal powder into the solution and stir for 2 hours at a stirring speed of 400 rpm to obtain a dispersion of binder-coated metal powder.

[0037] Powder mixing: Weigh 67 parts of polytetrafluoroethylene powder and add it to the dispersion obtained by coating the metal powder with the above binder. Stir for 3 hours at a stirring speed of 500 rpm to obtain a slurry; wherein the particle size of the polytetrafluoroethylene powder is 200 μm. (3) Microencapsulation The above slurry was emulsified in 500 mL of aqueous phase containing 1 part polyvinyl alcohol and ultrasonically dispersed for 0.5 h. Then, under nitrogen protection, the temperature was raised to 80 °C, and a mixed solution of 2 parts MMA and 0.1 parts benzoyl peroxide was slowly added dropwise to initiate polymerization for 6 h. After cooling, filtration, washing, and drying at 60 °C for 6 h, high molecular weight fluorinated polymer / metal powder microcapsules with polymethyl methacrylate (PMMA) shell were obtained. (4) Preparation of nano flame retardant coating Five parts of nano-aluminum hydroxide and 0.2 parts of sodium dodecyl sulfate were added to 200 mL of deionized water and ultrasonically dispersed for 1 h to prepare a composite nano flame retardant coating liquid. The microcapsule powder was placed in a fluidized bed and heated to 50 °C. The composite nano flame retardant coating liquid was sprayed at a rate of 0.5 mL / min until 5 parts of the composite nano flame retardant coating liquid were sprayed. After spraying, the fluidization was continued and the mixture was heated and dried for 4 h to finally form a continuous and dense nano composite flame retardant layer on the surface of the microcapsules. The nano-aluminum hydroxide had a particle size of 60 nm.

[0038] (5) Screening and packaging The sprayed powder was sieved through a sieve, and particles with a diameter of 170 μm were collected. The powder was then vacuum dried at 60 °C and 0.05 MPa for 4 hours. The powder was then sealed in a nitrogen-protected bag for later use, resulting in a safe and environmentally friendly microcapsule energetic material.

[0039] The combustion effect of the energetic material prepared according to Example 1 is as follows: Figure 3 As shown.

[0040] Example 2 The preparation method of a novel high-safety and environmentally friendly microcapsule energetic material with a nano-flame-retardant coating includes the following specific steps: (1) Modification of metal powder Surface modification: Weigh 1 part of epoxy silane and add it to ethyl acetate. Stir for 2 hours at a stirring speed of 150 rpm. Under nitrogen protection, disperse 45 parts of magnesium powder into the solution, soak for 6 hours, filter and dry to obtain modified metal powder. The active metal powder is spherical with a particle size of 10 μm.

[0041] (2) Preparation of core mixed slurry Coating: Weigh 2 parts of ethyl cellulose and add it to ethyl acetate. Stir for 3 hours at a stirring speed of 300 rpm until completely dissolved. Disperse the above 45 parts of modified metal powder into the solution and stir for 2 hours at a stirring speed of 400 rpm to obtain a dispersion of binder-coated metal powder. Mixing: Weigh 52 parts of polyvinylidene fluoride and add them to the dispersion of the above binder-coated metal powder. Stir for 3 hours at a stirring speed of 500 rpm to obtain a slurry; wherein the polyvinylidene fluoride powder has a particle size of 100 μm.

[0042] (3) Microencapsulation The above slurry was emulsified in 600 mL of aqueous phase containing 1 part polyvinyl alcohol and ultrasonically dispersed for 0.6 h. Then, under nitrogen protection, the temperature was raised to 65 °C, and 3 parts undecyllactam monomer and 0.3 parts ammonium persulfate were slowly added dropwise to initiate polymerization for 5 h. After the reaction was completed, the mixture was cooled, filtered, washed, and dried at 65 °C for 4 h to obtain polyundecyllactam (PA-11) shell-coated polymeric fluorinated polymer / metal powder microcapsules.

[0043] (4) Preparation of nano flame retardant coating Five parts of nano-silica and 0.3 parts of sodium polyacrylate dispersant were added to 150 mL of deionized water and ultrasonically dispersed for 0.7 h to prepare a composite nano flame retardant coating liquid. In a 60℃ spraying chamber, it was sprayed once at 0.7 mL / min, air-dried for 10 min, and then sprayed once more. After spraying, it was heated and dried at 65℃ for 6 h to finally form a continuous and dense nano-composite flame retardant layer on the surface of the microcapsules. The nano-silica particles had a diameter of 100 nm.

[0044] (5) Screening and packaging The sprayed powder was sieved through a sieve, and particles with a diameter of 150 μm were collected. The powder was then vacuum dried at 55 °C and 0.06 MPa for 6 hours. After drying, the powder was sealed in a nitrogen-protected bag for later use, thus obtaining a safe and environmentally friendly microcapsule energetic material.

[0045] Example 3 The preparation method of a novel high-safety and environmentally friendly microcapsule energetic material with a nano-flame-retardant coating includes the following specific steps: (1) Modification of metal powder Surface modification: Weigh 1 part of methacryloxysilane and add it to ethyl acetate. Stir for 2 hours at a stirring speed of 150 rpm. Under nitrogen protection, disperse 55 parts of boron powder into the solution, soak for 6 hours, filter and dry to obtain modified metal powder. The active metal powder is spherical with a particle size of 10 μm.

[0046] (2) Preparation of core mixed slurry Coating: Weigh 2 parts of fluororubber and add it to ethyl acetate. Stir for 3 hours at a stirring speed of 300 rpm until completely dissolved. Disperse the above 55 parts of modified metal powder into the solution and stir for 2 hours at a stirring speed of 400 rpm to obtain a dispersion of binder-coated metal powder. Mixing powder: Weigh 42 parts of polyhexafluoropropylene powder and add it to the dispersion obtained by the above fluororubber-coated metal powder. Stir for 3 hours at a stirring speed of 500 rpm to obtain a slurry; wherein the polyhexafluoropropylene powder has a particle size of 120 μm.

[0047] (3) Microencapsulation The above slurry was emulsified in 700 mL of aqueous phase containing 2 parts of polyvinyl alcohol and ultrasonically dispersed for 1 h. Then, under nitrogen protection, the temperature was raised to 70 °C, and 3 parts of ε-caprolactam monomer and 0.4 parts of ammonium persulfate were slowly added dropwise to initiate polymerization for 5 h. After the reaction was completed, the mixture was cooled, filtered, washed, and dried at 70 °C for 5 h to obtain poly(ε-caprolactam) (PA-6) shell-coated polymeric fluorinated polymer / metal powder microcapsules.

[0048] (4) Preparation of nano flame retardant coating Four parts of nano-alumina, one part of nano-silica, and 0.25 parts of sodium polyacrylate dispersant were added to 200 mL of ethanol and ultrasonically dispersed for 0.8 h to prepare a composite nano-flame retardant coating liquid. The coating liquid was sprayed once in a fluidized bed at 60 °C at a speed of 0.4 mL / min, and then sprayed again after weathering for 10 min. After spraying, the fluidized bed was kept at 60 °C and dried for 5 h to finally form a continuous and dense nano-composite flame retardant layer on the surface of the microcapsules. The nano-alumina particles had a diameter of 50 nm and the nano-silica particles had a diameter of 80 nm.

[0049] (5) Screening and packaging The sprayed powder was sieved through a sieve, and particles with a diameter of 180 μm were collected. The powder was then vacuum dried at 60 °C and 0.08 MPa for 6 hours. After drying, the powder was sealed in a nitrogen-protected bag for later use, thus obtaining a safe and environmentally friendly microcapsule energetic material.

[0050] Comparative Example 1: Energetic materials were prepared according to the method of Example 1, except that a flame-retardant coating was not applied (i.e., step 4 was omitted).

[0051] Comparative Example 2: Energetic materials were prepared according to the method in Example 1, except that microencapsulation and flame-retardant coating were not performed (i.e., steps 3 and 4 were omitted). The post-ignition effect was as follows: Figure 4 As shown.

[0052] The data obtained after safety performance testing of the safe and environmentally friendly microcapsule energetic materials prepared by Examples 1-3 above and the energetic materials prepared by Comparative Examples 1 and 2 are shown in Table 1 below.

[0053] Table 1 Safety Performance Test Data In recent years, polymeric fluorinated polymers / active metal powder systems have gradually become a research hotspot to replace traditional gunpowder due to their advantages such as high energy output, low smoke, sulfur- and nitrogen-free properties, mechanical insensitivity, and high safety. However, as civilian and military applications increasingly demand high reliability, long-term stability, and anti-aging performance under harsh conditions for energetic materials, single-material systems may struggle to meet multiple requirements, including moisture resistance, heat resistance, and delayed ignition.

[0054] Therefore, this invention utilizes microencapsulation technology to encapsulate the core active material with a polymer wall material. By controlling the composition and thickness of the wall material, the probability of external mechanical, frictional, or thermal stimuli being transmitted to the core is significantly reduced. Simultaneously, uniform particle dispersion and stable storage are achieved. Furthermore, introducing a nano-flame-retardant coating onto the surface of the microcapsule wall material can form a heat-insulating carbonized layer or release inert gas under high-temperature conditions, enhancing heat resistance and insulation performance, and further improving the safe storage and use performance of the energetic material. The energetic material prepared by the method of this invention, compared to black powder or other existing energetic materials, possesses advantages such as being sulfur- and nitrogen-free, environmentally friendly with minimal smoke, low mechanical sensitivity, high safety, heat resistance and insulation, controllable release, and stable storage, and can be widely applied in the production of civilian or military energetic materials.

[0055] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a safe and environmentally friendly microcapsule energetic material, characterized in that, Includes the following steps: S1: Preparation of surface-modified active metal powder; S2: The active metal powder described in S1 is coated with a binder and then mixed with a polymeric fluorinated polymer to obtain a polymeric fluorinated polymer / active metal powder core mixed slurry. S3: The slurry obtained in S2 is further emulsified in an aqueous phase containing a stabilizer, and a uniform emulsion with no obvious particle sedimentation is obtained by ultrasonic dispersion. The mixture is heated in an inert gas atmosphere, and monomers of the synthetic polymer coating material are uniformly added dropwise to the emulsion to initiate and maintain the polymerization reaction. After cooling, filtration, washing, and drying, polymer fluorinated polymer / active metal powder microcapsules with preliminary polymer coating material are obtained. S4: The polymer fluorinated polymer / modified active metal powder microcapsules obtained in S3 are coated to obtain polymer fluorinated polymer / active metal powder microcapsule energetic material particles with a continuous and dense nanocomposite flame retardant layer on the surface. S5: The high-molecular fluorinated polymer / active metal powder microcapsule energetic material particles obtained in S4 are screened and packaged to obtain safe and environmentally friendly microcapsule energetic material.

2. The preparation method according to claim 1, characterized in that, S1 specifically includes: S11: Add the silane coupling agent to the organic solvent and stir until homogeneous to obtain a mixed solution; S12: Under the protection of an inert gas atmosphere, the active metal powder is dispersed into the solution obtained in S11, soaked for a certain period of time, filtered and dried to obtain surface-modified active metal powder.

3. The preparation method according to claim 2, characterized in that: The silane coupling agent in S11 is one or more of aminosilane, epoxysilane, methacryloxysilane, mercaptosilane, vinylsilane, etc. The organic solvent in S11 is one or more of the following: ethyl acetate, acetone, toluene, xylene, n-hexane, cyclohexane, chloroform, dichloromethane, tetrahydrofuran, etc. The stirring time in S11 is 1~6h, and the stirring speed is 100~200rpm; The inert gas in S12 is composed of any one of nitrogen, argon, or helium. The active metal powder in S12 is one or more of the following: aluminum powder, magnesium powder, boron powder, zirconium powder, zinc powder, titanium powder, silicon powder, tin powder, etc. The soaking time in S12 is 6~12h.

4. The preparation method according to claim 1, characterized in that, S2 specifically includes: S21: Add the binder to the organic solvent and stir until completely dissolved; S22: Add the surface-modified active metal powder obtained in S1 to the binder-containing solution obtained in S21, stir for a certain time, and obtain a dispersion containing active metal powder coated with binder. S23: Add polymeric fluorinated polymer to the dispersion and continue stirring for a certain period of time to obtain a polymeric fluorinated polymer / active metal powder core mixed slurry.

5. The preparation method according to claim 4, characterized in that: The organic solvent in S21 is one or more of the following: ethyl acetate, acetone, toluene, xylene, n-hexane, cyclohexane, chloroform, dichloromethane, tetrahydrofuran, etc. The stirring time in S21 is 2-4 hours, and the stirring speed is 200-400 rpm. The binder in S21 is one or more of the following: nitrocellulose, ethyl cellulose, cellulose acetate, polymethyl methacrylate, polyvinyl acetate, epoxy resin, phenolic resin, fluororubber, hydroxyl-terminated polybutadiene, etc. The stirring time in S22 is 1~3h, and the stirring speed is 300~500rpm; The high molecular weight fluorinated polymer in S23 is any one or more of perfluoropolyether, polyvinylidene fluoride, polyfluoroolefin, polyfluoroalkane, and perfluoroethylene. The stirring time in S23 is 2-4 hours, and the stirring speed is 400-600 rpm.

6. The preparation method according to claim 1, characterized in that, In S3: The stabilizer is one or more of the following water-soluble polymeric emulsifiers with similar functions: polyvinyl alcohol, hydroxyethyl cellulose, sodium carboxymethyl cellulose, gelatin, gum arabic, polyvinylpyrrolidone, etc. The ultrasonic dispersion time is 0.5-1 hour, the temperature rise is 40-80℃, and the drying time is 4-6 hours. The inert gas is composed of any one of nitrogen, argon, or helium. The temperature rise range is from room temperature to 40-80℃, and the heating rate is 1~5°C / min. The synthetic polymer coating material is selected from any one or more of methyl methacrylate, styrene, acrylonitrile, ε-caprolactam, undecanolactam, acrylamide, etc. The polymerization reaction is maintained for 4-8 hours, and the drying time is 4-6 hours.

7. The preparation method according to claim 1, characterized in that, S4 specifically includes: S41: Nano flame retardant material and water-based wetting agent are added to deionized water or ethanol in a certain proportion and ultrasonically dispersed to prepare nano flame retardant coating liquid. S42: The nano flame-retardant coating liquid obtained in S41 is used to spray or dip the polymer fluorinated polymer / active metal powder microcapsules initially coated with polymer coating material obtained in S3 to obtain polymer fluorinated polymer / active metal powder microcapsule energetic material particles with a continuous and dense nanocomposite flame-retardant layer on the surface.

8. The preparation method according to claim 7, characterized in that: The nano flame retardant material in S41 is any one of nano alumina, nano aluminum hydroxide, nano silica or nano phosphorus flame retardant, or a combination of multiple of them. The aqueous wetting agent in S41 is one or more of the following: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium polyacrylate, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, sodium polyacrylate dispersant, etc. The ratio of the nano-flame retardant material to the water-based wetting agent in S41 is 1:0.01 to 1:0.2; The ultrasonic dispersion treatment in S41 takes 0.5 to 2 hours; The number of spraying or dipping treatments in S42 is 1-2 times, and the spraying or dipping rate is 0.4-0.8 mL / min.

9. The preparation method according to claim 1, characterized in that, In S5: The sieve used for the screening is 80-120 mesh. The particles obtained by sieving have a particle size of 150-180μm, and the particles are vacuum dried after sieving, wherein the vacuum drying pressure is <0.1Pa, the temperature is 50-60℃, and the time is 4-6h. The packaging uses a protective bag under inert gas protection.

10. A safe and environmentally friendly microcapsule energetic material, prepared by the preparation method according to any one of claims 1-9, characterized in that: The safe and environmentally friendly microcapsule energetic material is used in the field of environmentally friendly energetic materials.

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