Method for carrying out moisture absorption prevention treatment on superfine AP by using modified silicon dioxide

Abstract

The invention discloses a method for carrying out moisture absorption prevention treatment on superfine AP by using modified silicon dioxide, which comprises the following steps of: introducing a functional group structure on the surface of nano silicon dioxide by using a silane coupling agent to carry out low surface energy modification, and preparing modified nano silicon dioxide with super-hydrophobic performance; and adding the modified nano silicon dioxide particles into a superfine AP organic solvent, and carrying out ultrasonic treatment and stirring for a certain time to obtain superfine AP particles coated with the modified nano silicon dioxide. As the particle size of the AP particles is reduced, the specific surface area is increased, and the binding sites with the nano silicon dioxide particles are increased, so that the AP particles are relatively firmly coated on the surface of the AP. The nano silicon dioxide particles coated on the superfine AP can bring certain steric hindrance and simultaneously endow the superfine AP with certain hydrophobic performance, so that the superfine AP particles are prevented from moisture absorption, agglomeration and caking. The method is simple to operate, safe and efficient, the superfine AP is uniformly coated, and the hygroscopicity of the AP is obviously reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of AP modification, and in particular relates to a method for performing moisture absorption prevention treatment on ultrafine AP by using modified silicon dioxide. Background Art

[0002] Ammonium perchlorate (AP) is a high-energy oxidant with the advantages of high oxygen content, large formation enthalpy, good compatibility, no residue after combustion, and high stability at room temperature. Therefore, it is widely used in aerospace technology, explosive materials and other related fields. It accounts for a large proportion in solid propellants and is the main energy component of propellants. The smaller the particle size of AP, the faster its thermal decomposition and combustion rate, and the more heat it releases in a short time. At the same time, it can also increase the packing density in the propellant and improve the performance of the propellant.

[0003] However, AP molecules have strong polarity and have electrostatic attraction with water molecules in the air. + and ClO4 - It is easy to form hydrogen bonds with H and O of water molecules in the air. After AP absorbs moisture, its crystals will continue to dissolve and precipitate, and the continuous growth between the crystals will lead to agglomeration. At the same time, the reduction of AP particle size will increase the specific surface area, resulting in increased hygroscopicity and more obvious particle agglomeration, thus affecting the packing density, combustion performance and mechanical properties of AP in solid propellants.

[0004] Therefore, the improvement of AP moisture absorption problem is of great significance to the field of energetic materials and solid propellants. Chinese patent CN210410686U adopts a three-dimensional porous silica skeleton structure material, which is then modified with polymethylhydrogensiloxane to prevent AP moisture absorption through a sol-gel method. The problem of excessive addition has not been studied yet, and there is a lack of relevant experimental data. Its effect needs further study. Chinese patent CN110845285B adopts a coating method, using polyacrylate as a coating material and fluororubber as a crosslinking agent to coat AP. At 25°C and 100%RH, the moisture absorption rate of AP decreased by 78% after 24 hours. Liu Wei et al. used benzimidazole (BIM) and Co 2+AP@Co / BIM composites were prepared by coordination reaction on the surface of small-sized AP (s-AP) particles. When the Co / BIM content was 25 wt%, the moisture absorption rate of the AP@Co / BIM composite decreased by more than 90% after being placed in an environment of 40 ℃ and 88% RH for 72 h (GOU Xiaodong et al. In-situ synthesis of AP@Co / BIM composites with improved thermal performance and anti-hygroscopicity[J].Materials Chemistry and Physics, 2023, 309: 128347.). Ma Zhongliang et al. deposited benzimidazole and Zn on the surface of AP particles. 2+ The ZIF-7 layer formed. With the increase of ZIF-7 content, the contact angle of AP@ZIF-7 composite material with water increases and the hygroscopicity decreases. When the ZIF-7 content is 25wt%, the contact angle of AP@ZIF-7 increases by 66.09° compared with pure AP (GOUXiaodong et al. Preparation of AP@ZIF-7 composite materials by chemicalprecipitation method: A good strategy for simultaneously improving itsthermal performance, energy property and moisture absorption[J]. PowderTechnology, 2024, 433: 119230). Summary of the invention

[0005] The present invention discloses a method for treating ultrafine AP with modified silicon dioxide to prevent moisture absorption, and aims to provide a treatment method with simple operation, low implementation cost, low amount of modifier added, and uniform coating to reduce the moisture absorption rate of AP. The present invention uses nano-silicon dioxide to modify ultrafine AP. Nano-silicon dioxide has good chemical inertness, stable chemical properties, low density, large specific surface area, and abundant silanol groups on its surface. By introducing a functional group structure on the surface of nano-silicon dioxide, its strong agglomeration tendency is improved, and ultra-hydrophobic nano-silicon dioxide particles with low surface energy are simply and quickly prepared. After being combined with ultrafine AP, its moisture absorption characteristics can be significantly improved.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for treating ultrafine AP to prevent moisture absorption by using modified silicon dioxide comprises the following steps: (1) Preparation of modified nano-silica particles: Nano-silica is uniformly dispersed in ethanol, ammonia water and deionized water, and a silane coupling agent is added to react. After the reaction is completed, the modified nano-silica particles are obtained after washing, centrifugation and drying; (2) Preparation of ultrafine AP particles with surface modification of nano-silica particles: The modified nano-silica particles prepared in step (1) are added to an organic solvent in which ultrafine AP particles are uniformly dispersed, and ultrasonic stirring is performed to obtain ultrafine AP particles with surface modification of the modified nano-silica particles and anti-hygroscopic properties.

[0007] As an improvement of the present invention, the composition and content of the modified nano-silica particles in step (1) are as follows by mass percentage: 1-10% nano-silica, 60-80% ethanol, 10-30% ammonia water, 5-15% deionized water, and 1-10% silane coupling agent.

[0008] As an improvement of the present invention, the particle size of the silicon dioxide in step (1) is 1 to 100 nm.

[0009] As an improvement of the present invention, the silane coupling agent in step (1) is selected from at least one of γ-aminopropyltriethoxysilane, methyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, tridecafluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0010] As an improvement of the present invention, the reaction temperature in step (1) is 40-80° C. and the reaction time is 0.5-5 h.

[0011] As an improvement of the present invention, the centrifugal speed in step (1) is 3000-6000 rpm, and the centrifugal time is 5-10 min.

[0012] As an improvement of the present invention, in step (2), the particle size of the ultrafine AP is 50 nm~50 μm.

[0013] As an improvement of the present invention, in step (2), the organic solvent is selected from at least one of ethyl acetate, dichloromethane, chloroform, ether, isobutanol or oleic acid, and the dropping speed of the saturated solution is 20-40 mL / min.

[0014] As an improvement of the present invention, the mass ratio of the modified nano-silica particles to AP in step (2) is 1:100 to 1:20.

[0015] As an improvement of the present invention, in step (2), the ultrasonic frequency is 40 kHz, the ultrasonic power is 300 W, the ultrasonic time is 1 to 10 min, the stirring speed is 100 to 1500 r / min, and the stirring time is 1 to 10 min.

[0016] The beneficial effects of the present invention are: (1) The present invention adopts a wet coating method, in which modified nano-silica is added to an organic solvent in which AP is uniformly dispersed. Under the action of ultrasonic stirring, the modified nano-silica can be uniformly coated on the surface of ultrafine AP, bringing a certain steric hindrance and a certain hydrophobicity, which can effectively prevent the ultrafine AP from agglomerating, and is of great help for the long-term storage and transportation of ultrafine AP.

[0017] (2) The preparation of modified ultrafine AP by the present invention is simple, safe and efficient, requires a small amount of modifier, has a low implementation cost, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is the SEM image of the ultrafine AP and the modified ultrafine AP prepared in Example 1.

[0019] Figure 2 The water contact angle diagram of ultrafine AP and ultrafine AP with different proportions of nano-silica added.

[0020] Figure 3 This is a hygroscopicity curve of ultrafine AP and ultrafine AP with different proportions of nano-silica added. DETAILED DESCRIPTION

[0021] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0023] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0024] Example 1 (1) Take 1.5 g of silica, 15 g of ethanol, 3 g of ammonia water, 2 g of deionized water, and 0.8 g of methyltrimethoxysilane, a modifier, and add them into a three-necked flask with a stirrer and a condenser. The speed is 800 r / min, and the temperature is raised to 80°C for 2 h. After the reaction, wash it with ethanol several times, put it into a vacuum oven, and dry it at 60°C for 24 h to obtain nano-silica particles with a methylsilane structure on the surface, i.e., modified nano-silica.

[0025] (2) Add 5 g of ultrafine AP into the organic solvent ethyl acetate and stir magnetically for 20 min to make it evenly distributed to obtain an ultrafine AP suspension; add 0.05 g of modified nano-silica to the suspension and ultrasonicate for 5 min. The frequency and power of the ultrasound are 40 kHz and 300 W respectively. Stir for 5 min at a stirring rate of 200 rpm. After stirring, filter and dry to obtain a modified ultrafine AP with a coating amount of 1%.

[0026] Example 2 The method is basically the same as Example 1, except that the modified nano-silica in step (2) is 0.15 g, and a modified ultrafine AP with a coating amount of 3% is obtained.

[0027] Example 3 The method is basically the same as Example 1, except that the modified nano-silica in step (2) is 0.25 g, and a modified ultrafine AP with a coating amount of 5% is obtained.

[0028] As shown in the figure, Figure 1 Figures 2 and 3 are SEM images of ultrafine AP without modified nano-silica and modified ultrafine AP prepared in Example 1, wherein (A) is the SEM image of ultrafine AP without modified nano-silica, and (B) is the SEM image of modified ultrafine AP prepared in Example 1. As shown in the figure, the modified nano-silica prepared in Example 1 is uniformly coated on the surface of ultrafine AP particles.

[0029] Figure 2 The water contact angle diagram of the ultrafine AP without modified nano-silica and the modified ultrafine AP prepared in each embodiment is shown in FIG. The water contact angle of the ultrafine AP without modified nano-silica is 19.1°±0.7°, while the water contact angles of Embodiment 1, Embodiment 2, and Embodiment 3 are 36.5°±1.0°, 38.1°±6.1°, and 43.3°±1.3°, respectively, indicating that the addition of modified nano-silica can give the ultrafine AP a certain hydrophobic property. As the amount of modified nano-silica added increases, the hydrophobic property of the ultrafine AP is gradually enhanced.

[0030] The moisture absorption rate of the ultrafine AP without modified nano-silicon dioxide and the modified ultrafine AP prepared in each embodiment was tested at 30°C and 91% humidity for different time periods. The moisture absorption curve is shown in FIG. Figure 3 As shown in the figure, the moisture absorption rate of the ultrafine AP without modified nano-silica after 96 hours reached 0.23%, and with the increase of the amount of modified nano-silica added, the moisture absorption rate gradually decreased. The moisture absorption rates of Example 1, Example 2, and Example 3 after 96 hours were 0.16%, 0.14%, and 0.12%, respectively. The hygroscopicity of the ultrafine AP was effectively controlled.

[0031] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made on the basis of the above embodiments without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for treating ultrafine AP to prevent moisture absorption by using modified silica, characterized in that: The steps include: (1) Preparation of modified nano-silica particles: Nano-silica is uniformly dispersed in ethanol, ammonia water and deionized water, and a silane coupling agent is added to react. After the reaction is completed, the modified nano-silica particles are obtained after washing, centrifugation and drying; (2) Preparation of ultrafine AP particles with surface modification of nano-silica particles: The modified nano-silica particles prepared in step (1) are added to an organic solvent in which ultrafine AP particles are uniformly dispersed, and ultrasonic stirring is performed to obtain ultrafine AP particles with surface modification of the modified nano-silica particles and anti-hygroscopic properties.

2. The method for anti-hygroscopic treatment of ultrafine AP by modified silica according to claim 1, characterized in that: The particle size of the silicon dioxide in step (1) is 1-100 nm.

3. The method for anti-hygroscopic treatment of ultrafine AP by modified silica according to claim 1, characterized in that: The composition and content of the modified nano-silica particles in step (1) are as follows by mass percentage: 1-10% nano-silica, 60-80% ethanol, 10-30% ammonia water, 5-15% deionized water, and 1-10% silane coupling agent.

4. The method for anti-hygroscopic treatment of ultrafine AP by modified silica according to claim 1, characterized in that: In the step (1), the silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, methyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, tridecafluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

5. The method for anti-hygroscopic treatment of ultrafine AP by modified silicon dioxide according to claim 1, characterized in that: In the step (1), the reaction temperature is 40-80° C. and the reaction time is 0.5-5 h.

6. The method for anti-hygroscopic treatment of ultrafine AP by modified silicon dioxide according to claim 1, characterized in that: The centrifugal speed in step (1) is 3000-6000 rpm, and the centrifugal time is 5-10 min.

7. The method for anti-hygroscopic treatment of ultrafine AP by modified silicon dioxide according to claim 1, characterized in that: The particle size of the ultrafine AP in step (2) is 50 nm~50 μm.

8. The method for anti-hygroscopic treatment of ultrafine AP by modified silicon dioxide according to claim 1, characterized in that: The organic solvent in step (2) is selected from at least one of ethyl acetate, dichloromethane, chloroform, ether, isobutanol or oleic acid.

9. The method for anti-hygroscopic treatment of ultrafine AP by modified silicon dioxide according to claim 1, characterized in that: In the step (2), the mass ratio of the modified nano-silica particles to AP is 1:100 to 1:

20.

10. The method for anti-hygroscopic treatment of ultrafine AP by modified silicon dioxide according to claim 1, characterized in that: In the step (2), the ultrasonic frequency is 40 kHz, the ultrasonic power is 300 W, the ultrasonic time is 1 to 10 min, the stirring speed is 100 to 1500 r / min, and the stirring time is 1 to 10 min.

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