Preparation method and application of nitroguanidine propellant with core-shell structure based on coaxial electrostatic spraying technology

Abstract

The invention discloses a preparation method and application of a core-shell nitroguanidine propellant based on a coaxial electrostatic spraying technology. The preparation method comprises the following steps: dissolving nitroguanidine in a polar solvent to form a core layer solution; dissolving an insensitive high polymer material or a high-energy binder in a polar solvent to form a shell solution; a solution (an inner needle conveys a core layer solution and an outer needle conveys a shell layer solution) is sucked into an injector with a coaxial needle head, is fixed on an electrostatic sprayer and is received by an aluminum foil baffle, a positive electrode is connected to the needle head of the injector, a negative electrode is connected to the aluminum foil baffle, parameters are adjusted, and the solution forms stable spray with a taper angle of 20-60 degrees at a nozzle of the needle head; and atomizing in a high-voltage electrostatic field to obtain the nitroguanidine propellant with the core-shell structure. According to the nitroguanidine propellant with the core-shell structure, a core layer is high-energy nitroguanidine, a shell layer is an insensitive polymer or an energetic binder, and collaborative optimization of sensitivity reduction and energy release can be achieved; the shell layer can form a microporous structure by controlling the volatilization rate of the solvent, so that the combustion efficiency of the propellant powder is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of composite energetic materials and explosives, and in particular relates to a preparation method and application of a nitroguanidine propellant with a core-shell structure based on a coaxial electrostatic spraying technology. Background Art

[0002] Nitroguanidine (NQ) is a highly insensitive energetic material with a high detonation velocity (7650 m / s) and high work capacity. It can significantly improve the energy density and detonation performance of explosives, and is widely used as a component of explosives, propellants, and propellants. However, the needle- or rod-shaped nature of NQ crystals results in poor fluidity and mechanical properties. Furthermore, in a dry state and at high temperatures, NQ is highly sensitive to friction, impact, and flame, which can easily trigger explosions, limiting its military applications. Core-shell energetic materials have been a hot topic of research in recent years. These materials not only leverage the synergistic and reinforcing effects of various functional materials but also effectively prevent the aggregation of individual components during use. Currently, the main methods for preparing core-shell energetic materials include electroless plating, liquid-phase reduction, spray drying, and electrostatic spraying.

[0003] The basic principle of electrostatic spraying technology is to use a high-voltage electrostatic field to break down polymer solutions, dispersing charged droplets into extremely small droplets. It is widely used in fields such as biopharmaceuticals, food engineering, catalysis, and energy. However, composite energetic materials prepared using traditional single-needle electrostatic spraying methods cannot achieve a core-shell separation structure, and existing research has mostly focused on the field of sustained drug release. To address the poor fluidity and safety of nitroguanidine, the present invention studies a method for preparing a core-shell nitroguanidine propellant. This method can produce a spherical nitroguanidine energetic material with a core-shell structure. Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these objects and other advantages of the present invention, a method for preparing a nitroguanidine propellant with a core-shell structure based on a coaxial electrostatic spraying technique is provided, comprising the following steps: Step 1: dissolving nitroguanidine in a core layer polar solvent, heating and stirring to form a core layer solution; dissolving an insensitive polymer material or a high-energy binder in a shell layer polar solvent, ultrasonically treating and stirring to form a shell layer solution; Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, wherein the inner needle delivers the core layer solution and the outer needle delivers the shell layer solution. After inhalation, fix it on an electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. Adjust the process parameters so that the suspension forms a stable spray with a cone angle of 20~60° at the needle nozzle to obtain a core-shell structured nitroguanidine propellant.

[0006] Preferably, in step 1, the core layer polar solvent is one of dimethyl sulfoxide (DMSO), N,N-dimethylformamide, and a dimethyl sulfoxide-ethanol mixed solution, and the dosage ratio of nitroguanidine to the core layer polar solvent is: g / mL=1:10~1:20.

[0007] Preferably, in step one, the insensitive polymer material is one or more of hydroxy-terminated polybutadiene (HTPB), ethylene propylene diene monomer (EPDM), acrylic rubber (ACM), and paraffin; the high-energy binder is one or more of glycidyl azide (GAP), nitroglycerin, macroheterocyclobutane, and nitrocellulose (NC); the shell polar solvent is one or more of ethanol, ethyl acetate, acetone, and n-hexane; and the dosage ratio of the insensitive polymer material or high-energy binder to the shell polar solvent is: g / mL=1:10~1:40.

[0008] Preferably, in step 1, when preparing the core layer solution, the stirring time is 30-60 min, the heating temperature is 30-50° C., and the viscosity of the core layer solution is 1-200 mPa·s.

[0009] Preferably, in step 1, when preparing the shell solution, ultrasonication is performed at 40 kHz for 10 to 30 minutes, and then stirring is performed on a magnetic stirrer at room temperature for 10 to 30 minutes.

[0010] Preferably, in step 1, nitroguanidine accounts for 40-90 wt % of the total drug amount; the insensitive polymer material or high-energy binder accounts for 10-60 wt % of the total drug amount; wherein the total drug amount is the total mass of nitroguanidine plus the insensitive polymer material or high-energy binder.

[0011] Preferably, in step 2, the ratio of the core layer solution to the shell layer solution is 1:1 to 1:20.

[0012] Preferably, in step 2, the outer diameter of the nozzle of the coaxial needle is 0.32-3.45 mm, and the inner diameter is 0.16-2.95 mm.

[0013] Preferably, in step 2, the process parameters of electrospinning are: injection speed 0.1 μL~1 mL / min, DC high voltage power supply controlled at 10~30 kV, and collection distance between 10~50 cm.

[0014] Preferably, in step one, when preparing the core layer solution, polyvinyl pyrrolidone (PVP) is added to the core layer polar solvent, and the amount of polyvinyl pyrrolidone added is 0.5~1wt% of the nitroguanidine; when preparing the shell layer solution, nano-molybdenum disulfide is added to the shell layer polar solvent, and the amount of nano-molybdenum disulfide added is 0.5~1wt% of the insensitive polymer material or high-energy binder.

[0015] The present invention also provides an application of a nitroguanidine propellant with a core-shell structure, wherein the nitroguanidine propellant with a core-shell structure is used as a propellant for explosives or propellants.

[0016] The present invention has at least the following beneficial effects: The core-shell structured nitroguanidine propellant prepared by the present invention comprises a core layer of high-energy nitroguanidine and a shell layer of an insensitive polymer or an energetic binder, thereby achieving synergistic optimization of sensitivity reduction and energy release. Furthermore, by controlling the solvent volatilization rate, the shell layer can be formed into a microporous structure, thereby improving the combustion efficiency of the propellant. The present invention uses less solvent in the preparation process, has low cost, light droplet drift, and a safe production process. The high-energy insensitive aluminum-containing explosive prepared by the method of the present invention has a particle size range of 2 to 10 μm. Furthermore, the present invention adds PVP to the core layer solution to inhibit nitroguanidine from forming needle-shaped or rod-shaped crystals, thereby improving the fluidity of nitroguanidine. Nano-molybdenum disulfide is also added to the shell layer solution to reduce the friction of the shell layer, thereby improving the impact strength.

[0017] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an SEM image of the core-shell nitroguanidine propellant prepared in Example 1 of the present invention; Figure 2 This is a flow chart of the coaxial electrostatic spraying process prepared in Example 3 of the present invention. DETAILED DESCRIPTION The present invention will be further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description. It should be understood that terms such as "having", "including" and "comprising" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0019] Example 1 A method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spray technology comprises the following steps: Step 1: Dissolve 1g of nitroguanidine (NQ) in 10mL of DMSO, heat to 40°C on a magnetic stirrer, and stir for 30 minutes to form a homogeneous core solution with a viscosity of 200mPa·s. Dissolve 1g of nitrocellulose (NC) in 20mL of acetone, sonicate at 40kHz for 30 minutes to break up the molecular chains, and then stir at room temperature on a magnetic stirrer for 10 minutes to form a shell solution. Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, where the inner needle transports the core layer solution and the outer needle transports the shell solution. After inhalation, fix it on the electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. The flow rate is controlled at 0.1 mL / min and the high-voltage power supply is controlled at 14 kV so that the solution forms a Taylor cone with a cone angle of 30° at the needle nozzle to obtain a core-shell structured NQ / NC propellant.

[0020] Figure 1 This is an SEM image of the core-shell structured nitroguanidine propellant prepared in Example 1 of the present invention. As can be seen from the figure, the NQ / NC propellant prepared by coaxial electrostatic spraying is spherical with a particle size of about 4 μm; the surface of the particles is rough, indicating that NC is successfully coated on the surface of NQ to form a core-shell structure.

[0021] Example 2 A method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spray technology comprises the following steps: Step 1: Dissolve 1g of nitroguanidine (NQ) in 10mL of a 1:1 mixture of DMSO and ethanol. Heat to 30°C on a magnetic stirrer and stir for 30 minutes to form a homogeneous core solution with a viscosity of 150mPa·s. Dissolve 1g of glycidyl azide (GAP) in 20mL of acetone and sonicate at 40kHz for 20 minutes to break up the molecular chains. Stir at room temperature for 15 minutes on a magnetic stirrer to form a shell solution. Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, where the inner needle transports the core layer solution and the outer needle transports the shell solution. After inhalation, fix it on the electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. The flow rate is controlled at 0.2 mL / min and the high-voltage power supply is controlled at 13.5 kV so that the solution forms a Taylor cone with a cone angle of 30° at the needle nozzle to obtain a core-shell structured NQ / GAP propellant.

[0022] Example 3 A method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spray technology comprises the following steps: Step 1: Dissolve 1g of nitroguanidine (NQ) in 10mL of a 1:1 mixture of DMSO and ethanol. Heat to 30°C on a magnetic stirrer and stir for 30 minutes to form a homogeneous core solution with a viscosity of 150mPa·s. Dissolve 1g of hydroxy-terminated polybutadiene (HTPB) in 10mL of ethyl acetate and sonicate at 40kHz for 20 minutes to break up the molecular chains. Stir at room temperature for 20 minutes on a magnetic stirrer to form a shell solution. Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, where the inner needle delivers the core layer solution and the outer needle delivers the shell solution. After inhalation, fix it on the electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. The flow rate is controlled at 0.1 mL / min and the high-voltage power supply is controlled at 12.8 kV so that the solution forms a Taylor cone with a cone angle of 30° at the needle nozzle to obtain a core-shell structured NQ / HTPB propellant.

[0023] Figure 2 This is a flow chart of the coaxial electrostatic spraying process for preparing a core-shell structured NQ / HTPB propellant according to Example 3 of the present invention. The electrostatic spraying coaxial needle is a special nozzle design with a dual liquid inlet design that can simultaneously inject two different mixed solutions, thereby forming a core-shell structure with an inner layer (NQ) and an outer layer (HTPB) of different materials. This allows the resulting core-shell structure to have better safety and mechanical properties.

[0024] Example 4 A method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spray technology comprises the following steps: Step 1: Dissolve 1g of nitroguanidine (NQ) in 10mL of DMSO, then add 0.01g of polyvinylpyrrolidone. Heat to 40°C on a magnetic stirrer and stir for 30 minutes to form a homogeneous core solution with a viscosity of 200mPa·s. Dissolve 1g of nitrocellulose (NC) in 20mL of acetone and sonicate at 40kHz for 30 minutes to break up the molecular chains. Stir at room temperature for 10 minutes on a magnetic stirrer to form a shell solution. Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, where the inner needle transports the core layer solution and the outer needle transports the shell solution. After inhalation, fix it on the electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. The flow rate is controlled at 0.1 mL / min and the high-voltage power supply is controlled at 14 kV so that the solution forms a Taylor cone with a cone angle of 30° at the needle nozzle to obtain a core-shell structured NQ / NC propellant.

[0025] Example 5 A method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spray technology comprises the following steps: Step 1: Dissolve 1g of nitroguanidine (NQ) in 10mL of DMSO, then add 0.01g of polyvinyl pyrrolidone, heat to 40°C on a magnetic stirrer, and stir for 30 minutes to form a uniform core layer solution with a viscosity of 200mPa·s. Dissolve 1g of nitrocellulose (NC) in 20mL of acetone, then add 0.01g of nano-molybdenum disulfide, sonicate at 40kHz for 30 minutes to break the entanglement between the molecular chains, and then stir at room temperature for 10 minutes on a magnetic stirrer to form a shell layer solution. Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, where the inner needle transports the core layer solution and the outer needle transports the shell solution. After inhalation, fix it on the electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. The flow rate is controlled at 0.1 mL / min and the high-voltage power supply is controlled at 14 kV so that the solution forms a Taylor cone with a cone angle of 30° at the needle nozzle to obtain a core-shell structured NQ / NC propellant.

[0026] Comparative Example 1 This comparative example is a conventional composite NQ / GAP propellant, and the preparation method is as follows: 1 g of nitroguanidine (NQ) and 1 g of glycidyl azide (GAP) are added together to 10 mL of a mixed solvent of DMSO and ethanol (the ratio of DMSO to ethanol is 1:1), heated to 30°C on a magnetic stirrer, and stirred for 30 minutes to form a uniform solution with a viscosity of 150 mPa·s; then the above solution is slowly injected into 50 mL of n-heptane, stirred, filtered, and dried to obtain the NQ / GAP propellant.

[0027] Comparative Example 2 This comparative example is a conventional composite NQ / HTPB propellant, and the preparation method is as follows: take 1g of nitroguanidine (NQ) and 1g of hydroxypolybutadiene (HTPB) and add them together to 10mL of a mixed solvent of DMSO and ethanol (the ratio of DMSO to ethanol is 1:1), heat to 30°C on a magnetic stirrer, and stir for 30 minutes to form a uniform solution with a viscosity of 150mPa·s; then slowly inject the above solution into 50ml of n-heptane, stir, filter, and dry to prepare the NQ / HTPB propellant.

[0028] The propellants prepared in the examples and comparative examples were subjected to impact strength tests, and the results are shown in Table 1 below.

[0029] Table 1 As can be seen from Table 1, compared with Comparative Examples 1-2, Examples 1-3 of the present invention use coaxial electrostatic spraying technology, use insensitive polymer materials or high-energy binders as shell layers, and use nitroguanidine as a core layer and wrap it inside, which greatly reduces the sensitivity of the prepared propellant, thereby greatly improving the impact strength of the propellant at different temperatures. In addition, Example 4 of the present invention is based on Example 1. When preparing the core layer solution, polyvinyl pyrrolidone is introduced to inhibit the formation of needle-like whiskers of nitroguanidine, further reducing the sensitivity to friction, flame, etc., and improving the fluidity of nitroguanidine, which is manifested as improved impact strength. Example 5 is based on Example 4. When preparing the shell layer solution, nano-molybdenum disulfide is introduced. Nano-molybdenum disulfide has a good lubricating effect and can effectively improve the lubricity and fluidity of the insensitive polymer material or high-energy binder shell layer, so as to reduce the friction of the propellant and thereby improve the impact strength.

[0030] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a core-shell nitroguanidine propellant based on coaxial electrostatic spray technology, characterized in that: The following steps are involved: Step 1: dissolving nitroguanidine in a core layer polar solvent, heating and stirring to form a core layer solution; dissolving an insensitive polymer material or a high-energy binder in a shell layer polar solvent, ultrasonically treating and stirring to form a shell layer solution; Step 2: Use a syringe with a coaxial needle to simultaneously inhale the core layer solution and the shell layer solution, wherein the inner needle delivers the core layer solution and the outer needle delivers the shell layer solution. After inhalation, fix it on an electrostatic sprayer and receive it with an aluminum foil baffle. The positive electrode is connected to the needle of the syringe and the negative electrode is connected to the aluminum foil baffle. Adjust the process parameters so that the suspension forms a stable spray with a cone angle of 20~60° at the needle nozzle to obtain a core-shell structured nitroguanidine propellant.

2. The method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spraying technology according to claim 1, wherein: In the step 1, the core layer polar solvent is one of dimethyl sulfoxide, N,N-dimethylformamide, and a dimethyl sulfoxide-ethanol mixed solution, and the dosage ratio of nitroguanidine to the core layer polar solvent is: g / mL=1:10~1:

20.

3. The method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spraying technology according to claim 1, wherein: In the step 1, the insensitive polymer material is one or more of hydroxy-terminated polybutadiene, EPDM rubber, acrylic rubber, and paraffin; the high-energy binder is one or more of azido glycidyl ether, nitroglycerin, macroheterocyclobutane, and nitrocellulose; the shell polar solvent is one or more of ethanol, ethyl acetate, acetone, and n-hexane; and the dosage ratio of the insensitive polymer material or high-energy binder to the shell polar solvent is: g / mL=1:10~1:

40.

4. The method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spraying technology according to claim 1, wherein: In the step 1, when preparing the core layer solution, the stirring time is 30-60 minutes, the heating temperature is 30-50° C., and the viscosity of the core layer solution is 1-200 mPa·s.

5. The method for preparing a nitroguanidine propellant with a core-shell structure based on coaxial electrostatic spraying technology as claimed in claim 1, characterized in that: In the step 1, when preparing the shell solution, ultrasonication is performed at 40 kHz for 10 to 30 minutes, and then stirring is performed on a magnetic stirrer at room temperature for 10 to 30 minutes.

6. The method for preparing a core-shell nitroguanidine propellant based on coaxial electrostatic spraying technology according to claim 1, characterized in that: In step 1, nitroguanidine accounts for 40-90 wt % of the total drug amount; the insensitive polymer material or high-energy binder accounts for 10-60 wt % of the total drug amount; the total drug amount is the total mass of nitroguanidine plus the insensitive polymer material or high-energy binder.

7. The method for preparing a core-shell nitroguanidine propellant based on coaxial electrostatic spraying technology according to claim 1, characterized in that: In the step 2, the ratio of the core layer solution to the shell layer solution is 1:1 to 1:

20.

8. The method for preparing a core-shell nitroguanidine propellant based on coaxial electrostatic spraying technology according to claim 1, wherein: In the step 2, the outer diameter of the nozzle of the coaxial needle is 0.32-3.45 mm, and the inner diameter is 0.16-2.95 mm.

9. The method for preparing a core-shell nitroguanidine propellant based on coaxial electrostatic spraying technology according to claim 1, wherein: In the step 2, the process parameters of electrospinning are: injection speed 0.1 μL~1 mL / min, DC high voltage power supply controlled at 10~30 kV, and collection distance between 10~50 cm.

10. An application of a nitroguanidine propellant with a core-shell structure prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The nitroguanidine propellant with a core-shell structure is used as a propellant for explosives or propellants.

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