Application of cyclodextrin potassium metal organic framework as flame extinguisher in the preparation of propellant

Abstract

The invention discloses the use of a cyclodextrin potassium metal organic framework as a flame extinguisher in the preparation of propellants. The invention mixes the cyclodextrin potassium metal organic framework with dry nitrocellulose, adds acetone and ethanol to mix evenly, and then extrude into a tubular structure of NC@CD-MOF propellant. The cyclodextrin potassium metal organic framework has good compatibility and flame suppression with nitrocellulose, the main energy material for propellants. When used as a flame extinguisher, the flame extinguishing element potassium in the cyclodextrin potassium metal organic framework is easy to decompose and release compared with inorganic potassium salts, and the hygroscopicity of a certain amount of cyclodextrin potassium metal organic framework is reduced after being compounded with nitrocellulose, which is beneficial to the storage stability of nitrocellulose, thereby obtaining a high-efficiency flame extinguisher with long storage performance that meets the use requirements, reducing the muzzle flame generated when a barreled weapon is fired, and will not affect the ballistic performance of the ammunition.

Description

Technical Field

[0001] The invention belongs to the field of flame extinguishers for propellants, and relates to the application of a cyclodextrin potassium metal organic framework as a flame extinguisher in the preparation of propellants. Background Art

[0002] High initial velocity and long range are the hallmarks of long-range suppression and efficient destruction of barreled weapons in modern warfare. The advanced nature of advanced artillery propulsion technology is often reflected in the ability to significantly increase the muzzle kinetic energy, and use this as a means to increase the lethality and comprehensive combat effectiveness of the weapon system (Xiao Zhongliang, Introduction to Explosives [M]. Beijing: National Defense Industry Press, 2019.). Energy-releasing progressive propellants play a vital role in improving the muzzle kinetic energy of barreled weapons. At present, energy-increasing propellants can be divided into burning surface progressive propellants and burning rate progressive propellants. Among them, the burning rate progressive combustion is obtained by the change of the chemical composition of each burning layer of the propellant, which can be achieved by surface insensitivity or coating methods. It is an important technical approach for small and medium-caliber weapons to obtain excellent ballistic effects of "high initial velocity and low chamber pressure". However, small molecule insensitive agents are easy to migrate in the propellant, resulting in "ballistic drift"; the "inert" components in the coated and insensitive propellant aggravate the negative oxygen balance of the formula, resulting in the formation of harmful phenomena such as gun / gun muzzle smoke, flame and residue (Liu Bo, Zheng Shuang, Liu Shaowu, et al. Research on reducing muzzle flame with flame suppressant [J]. Energetic Materials, 2012, 20(01): 80-82.). In addition, high-energy propellants and high-density charge structures are also used to further increase the muzzle kinetic energy of the projectile, but under the condition of large charge amount, it will lead to an increase in the intensity of the gun (gun) muzzle flame.

[0003] The flame and smoke performance of propellant charge has always been a research focus in the development of weapons and equipment. The large amount of smoke or flame produced by barreled weapons during firing will expose the weapon launch position in combat and will immediately be attacked by enemy artillery fire, which is even more important for naval ships. Strong secondary flames will affect the detection, locking and target tracking functions of the optoelectronic system of guided weapons, and even burn gunners, seriously affecting combat. At present, adding inorganic alkali metal salts such as sodium salts or potassium salts is an effective means to suppress the muzzle flame of guns (cannons). However, inorganic alkali metal salts, such as potassium nitrate (KNO3), potassium sulfate (K2SO4) and potassium bicarbonate (KHCO3), have problems such as poor dispersibility, strong hygroscopicity and difficulty in decomposition [Song Yufang, Xiao Leqin, Suga Xiaoxia, et al. Synthesis and application of low molecular weight potassium polyacrylate ([J]. Explosive Materials, 2019, 48(05): 40-45.; J. Lavoie, C.-F. Petre, S. Durand, C. Dubois, Stability and performance of gun propellants incorporating 3,6-dihydrazino-s-tetrazine and 5-aminotetrazolium nitrate, J. Hazard. Mater. 363 (2019) 457-463.), which leads to the accelerated autocatalysis and aging of nitrocellulose, the reduction of overall mechanical properties, and the reduction of the accuracy of weapon guidance. However, organic potassium salts, such as potassium fluoroaluminate, potassium hexafluoroaluminate (K3AlF6) and potassium benzoate (C7H5KO2), are limited due to the presence of combustion residues and the impact on the ballistic stability of barreled weapons (He Yun, Zhao Qilin, Chen Chunlin, et al. Research on the performance of spherical (flat) propellants containing potassium hexanitrocobaltate flame retardant [J]. Journal of Ordnance Equipment Engineering, 2021, 42(09): 259-263.).

[0004] Cyclodextrin potassium metal-organic framework (CD-MOF) is composed of organic ligand cyclodextrin and central potassium (K) metal ions. Due to its strong crystallinity, permanent porosity and good biocompatibility, CD-MOF has shown potential applications in various fields. However, CD-MOF as a flame extinguisher has not been reported at all. Summary of the invention

[0005] In view of the problems existing in the existing traditional flame extinguishers, the present invention provides an application of a cyclodextrin potassium metal organic framework as a flame extinguisher in the preparation of propellants. The cyclodextrin potassium metal organic framework is used as a flame extinguisher in the propellant, which can effectively reduce the muzzle flame of a barreled weapon gun (cannon) without destroying the storage stability and ballistic stability of the propellant.

[0006] The technical solution of the present invention is as follows:

[0007] The application of cyclodextrin potassium metal organic framework as a flame extinguisher in the preparation of propellant is as follows:

[0008] After the cyclodextrin potassium metal organic framework and dry nitrocellulose are evenly mixed, a mixed solvent of acetone and ethanol in a volume ratio of 1:1 is added, stirred until the mixture is evenly mixed, extruded into a tubular structure, and dried to obtain NC@CD-MOF propellant.

[0009] Preferably, the potassium cyclodextrin metal organic framework is selected from α-cyclodextrin potassium metal organic framework (α-CD-MOF), β-cyclodextrin potassium metal organic framework (β-CD-MOF) or γ-cyclodextrin potassium metal organic framework (γ-CD-MOF).

[0010] Preferably, the type of nitrocellulose is grade A nitrocellulose, grade B nitrocellulose or grade E nitrocellulose.

[0011] Preferably, the mass ratio of cyclodextrin potassium metal organic framework to nitrocellulose is 0.015:1 to 0.05:1.

[0012] Preferably, the mass ratio of the mixed solvent to the nitrocellulose is 0.58:1 to 0.63:1.

[0013] Preferably, the stirring time is 30 min to 60 min.

[0014] Preferably, the drying method is drying in an oven at 45° C. until the volatile matter is reduced to 1%.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention uses low-cost and environmentally friendly cyclodextrin potassium metal organic framework as a flame extinguishing agent for propellants. The cyclodextrin potassium metal organic framework is easy to decompose and will not decompose to produce toxic and harmful substances. It also contains the flame extinguishing element potassium and has good compatibility with the main component of the propellant, nitrocellulose, which makes the cyclodextrin potassium metal organic framework have certain flame retardant and flame extinguishing capabilities.

[0017] (2) The cyclodextrin potassium metal organic framework of the present invention has good compatibility with nitrocellulose, the main component of the propellant, and has obvious flame extinguishing effect without destroying the storage stability and ballistic stability of the propellant. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Differential scanning calorimetry (DSC) analysis curves and comprehensive thermal analysis of NC, NC@α-CD-MOF-1%, NC@β-CD-MOF-1%, and NC@γ-CD-MOF-1% prepared in Comparative Example 1, Examples 1, 2, and 3.

[0019] Figure 2This is the X-ray diffraction pattern (XRD) of β-CD-MOF prepared in Example 2.

[0020] Figure 3 The scanning electron microscope (SEM), polarizing microscope, and EDS energy spectrum diagram of the β-CD-MOF prepared in Example 2 are shown.

[0021] Figure 4 This is the thermogravimetric spectrum (TG) of β-CD-MOF and KNO3 prepared in Example 2.

[0022] Figure 5 The compatibility analysis diagram of β-CD-MOF and NC prepared in Example 2. GJB770B method 502.1 was used, and the heating rates from 100°C to 300°C were 2, 5, 10 and 20°C·min respectively. -1 .

[0023] Figure 6 This is the morphology of NC@β-CD-MOF-1% prepared in Example 2.

[0024] Figure 7 The flame morphology of NC@β-CD-MOF-1% and NC@KNO3-1% tubular propellants prepared in Example 2 and Comparative Example 2 is as follows: the prepared granular propellant sample is placed vertically on an ignition bracket, and then the ignition bracket is placed in a four-window combustion chamber, pressurized with nitrogen (3MPa), and the flame structure is recorded through the window by a high-speed camera at 20°C.

[0025] Figure 8 The static combustion performance test diagram of NC, NC@β-CD-MOF-1%, and NC@KNO3-1% tubular propellants prepared in Comparative Example 1, Example 2, and Comparative Example 2. A certain amount of sample was placed in a closed explosive device at a test temperature of 20°C. Based on the packing density of the test sample of 0.12 g·mL -1 . DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings, but the protection scope of the present invention is not limited to the following.

[0027] In the following examples, a scanning electron microscope (SEM) was used to analyze the surface morphology of the samples, a closed detonator was used to test the static combustion performance of the samples, and a four-window combustion chamber and high-speed photography were used to test the flame extinguishing performance.

[0028] Example 1

[0029] Accurately weigh 2g of α-CD-MOF with an average particle size of 0.15mm as a flame extinguisher. Mix 2g of α-CD-MOF flame extinguisher with 200g of dried NC and add them to a horizontal sigma kneader. Weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent doped with α-CD-MOF for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC@α-CD-MOF-1% propellant. Finally, the sample is dried in an oven at 45°C until the volatiles are reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0030] Example 2

[0031] Accurately weigh 2g of β-CD-MOF with an average particle size of 0.15mm as a flame extinguisher. Mix 2g of β-CD-MOF flame extinguisher with 200g of dried NC and add them to a horizontal sigma kneader. Weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent doped with β-CD-MOF for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC@β-CD-MOF-1% propellant. Finally, the sample is dried in an oven at 45°C until the volatiles are reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0032] Example 3

[0033] Accurately weigh 2g of γ-CD-MOF with an average particle size of 0.15mm as a flame extinguisher. Mix 2g of γ-CD-MOF flame extinguisher with 200g of dried NC and add them to a horizontal sigma kneader. Weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent doped with γ-CD-MOF for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC@γ-CD-MOF-1% propellant. Finally, the sample is dried in an oven at 45°C until the volatiles are reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0034] Example 4

[0035] Accurately weigh 6g of β-CD-MOF with an average particle size of 0.15mm as a flame extinguisher. Mix 6g of β-CD-MOF flame extinguisher with 200g of dried NC and add it to a horizontal sigma kneader. Weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent doped with β-CD-MOF for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC@β-CD-MOF-3% propellant. Finally, the sample is dried in an oven at 45°C until the volatiles are reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0036] Example 5

[0037] Accurately weigh 10g of β-CD-MOF with an average particle size of 0.15mm as a flame extinguisher. Mix 10g of β-CD-MOF flame extinguisher with 200g of dried NC and add it to a horizontal sigma kneader. Weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent doped with β-CD-MOF for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC@β-CD-MOF-5% propellant. Finally, the sample is dried in an oven at 45°C until the volatiles are reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0038] Comparative Example 1

[0039] Weigh 200g of dry NC and add it to a horizontal sigma kneader, weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC propellant. Finally, the sample is dried in an oven at 45°C until the volatile matter is reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0040] Comparative Example 2

[0041] Accurately weigh 2g of KNO3 with an average particle size of 0.15mm as a flame extinguisher. Mix 2g of KNO3 flame extinguisher with 200g of dry NC and add it to a horizontal sigma kneader. Weigh 60g of acetone and 60g of ethanol, stir evenly to obtain a mixed solution, add it to the kneader, and stir and mix the NC solvent doped with KNO3 for 1 hour. Then use a hydraulic press to extrude the propellant dough into a tubular structure to obtain NC@KNO3-1% propellant. Finally, the sample is dried in an oven at 45°C until the volatile matter is reduced to 1%. The sample is tested for flame morphology, static combustion performance, etc.

[0042] Figure 1 Table 1 shows the differential scanning calorimetry (DSC) analysis curves and comprehensive thermal analysis of NC, NC@α-CD-MOF-1%, NC@β-CD-MOF-1%, and NC@γ-CD-MOF-1% prepared in Comparative Example 1, Examples 1, 2, and 3. It can be seen that the heat release sizes are: NC (1596 J·g -1 )>NC@α-CD-MOF-1%(1555J·g -1 )>NC@β-CD-MOF-1%(1094J·g -1 )>NC@γ-CD-MOF-1%(1015J·g -1 ). The initial decomposition temperatures (T0) are NC (200.1℃) > NC@α-CD-MOF-1% (199.1℃) > NC@β-CD-MOF-1% (198.8℃) > NC@γ-CD-MOF-1% (197.0℃). After adding the CD-MOF series flame retardant, the overall heat release of the sample decreased, and the initial decomposition temperature was slightly advanced. In this regard, the use of CD-MOF should be considered in a comprehensive and balanced manner.

[0043] Table 1 Comprehensive thermal analysis of NC, NC@α-CD-MOF-1%, NC@β-CD-MOF-1%, NC@γ-CD-MOF-1%

[0044]

[0045] Figure 2 This is the X-ray diffraction test pattern (XRD) of β-CD-MOF. The results show that characteristic peaks of β-CD-MOF appear at 4.5° (001), 6.4° (10-1) and 9.2° (002).

[0046] Figure 3 The following are the scanning electron microscope test images (SEM), polarizing microscope images and EDS spectrum test images of β-CD-MOF. The results show that the β-CD-MOF crystal has a cubic structure and a smooth surface. In addition, the EDS spectrum shows the uniform distribution of C, O and K elements in the β-CD-MOF sample.

[0047] Figure 4 The thermogravimetric data spectra (TG) of the prepared β-CD-MOF and the traditional flame extinguisher KNO3. Compared with the traditional flame extinguisher KNO3 (605℃~830℃), β-CD-MOF is more likely to decompose at a lower temperature, which indicates that β-CD-MOF is more likely to release the flame extinguishing element potassium (K).

[0048] Figure 5The compatibility analysis diagram of the prepared β-CD-MOF and NC. The results show that the addition of β-CD-MOF has little effect on the exothermic peak temperature of NC (within an acceptable range of variation, 2°C). These results illustrate that NC and β-CD-MOF have no chemical reaction at low temperatures and have good compatibility. Therefore, β-CD-MOF can be used as an additive component for propellants, propellants, and explosives.

[0049] Table 2 shows the hygroscopicity analysis of NC@β-CD-MOF with different addition amounts under different humidity conditions. It can be seen that with the decrease in the addition amount of β-CD-MOF, this is attributed to the close intermolecular hydrogen bond network established between β-CD-MOF and NC, and the hygroscopicity of the sample is reduced to a certain extent, which is beneficial to the storage stability of the propellant.

[0050] Table 2 Hygroscopicity analysis of different addition amounts of NC@β-CD-MOF under different humidity conditions

[0051]

[0052]

[0053] Figure 6 This is the morphology of NC@β-CD-MOF-1% prepared in Example 2. It can be seen that the flame extinguisher CD-MOF is evenly distributed in NC.

[0054] Figure 7 The flame morphology diagrams of the NC@β-CD-MOF-1% tubular propellant prepared in Example 2 and the NC@KNO3-1% tubular propellant prepared in Comparative Example 2 show that the flame area and flash of the propellant containing β-CD-MOF are the smallest compared with those of the propellant containing KNO3, indicating that β-CD-MOF has a better flame extinguishing effect.

[0055] Figure 8 The static combustion performance test diagrams of the NC prepared in comparative example 1, NC@β-CD-MOF-1% prepared in example 2, and NC@KNO3-1% tubular propellant prepared in comparative example 1. There is almost no difference in the LB curve shape between the original NC propellant and the propellant containing β-CD-MOF, and both have good combustion consistency.

Claims

1. The use of cyclodextrin potassium metal organic framework as a flame extinguisher in the preparation of propellant, characterized in that: The specific method is: After the cyclodextrin potassium metal organic framework and the dried nitrocellulose are evenly mixed, a mixed solvent of acetone and ethanol in a volume ratio of 1:1 is added, and the mixture is stirred until evenly mixed, extruded into a tubular structure, and dried to obtain the NC@CD-MOF propellant. The mass ratio of the cyclodextrin potassium metal organic framework to the nitrocellulose is 0.01:1 or 0.015:1~0.05:

1.

2. The use according to claim 1, characterized in that: The potassium cyclodextrin metal organic framework is selected from α-potassium cyclodextrin metal organic framework, β-potassium cyclodextrin metal organic framework or γ-potassium cyclodextrin metal organic framework.

3. The use according to claim 1, characterized in that: The types of nitrocellulose are grade A nitrocellulose, grade B nitrocellulose or grade E nitrocellulose.

4. The use according to claim 1, characterized in that: The mass ratio of the mixed solvent to nitrocellulose is 0.58:1~0.63:

1.

5. The use according to claim 1, characterized in that: The stirring time is 30 min to 60 min.

6. The use according to claim 1, characterized in that: The drying method is to dry in an oven at 45°C until the volatile matter is reduced to 1%.

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