An in-situ modified spherical ADN moisture-wicking composite material and its preparation method

Abstract

This invention relates to the field of explosives technology, specifically disclosing an in-situ modified spherical ADN moisture-resistant composite material and its preparation method. The method includes adding crude ADN powder, a modifier, and an emulsifier to a dispersion medium and stirring to obtain an ADN particle dispersion; heating, stirring, and maintaining the temperature of the ADN particle dispersion to form a surface-modified ADN molten emulsion; cooling the surface-modified ADN molten emulsion to promote the aggregation of surface-modified ADN molten emulsion droplets into spheres, obtaining an in-situ modified spherical ADN moisture-resistant composite material suspension; transferring the in-situ modified spherical ADN moisture-resistant composite material suspension to a vacuum filter to achieve solid-liquid separation; transferring the solid to a vacuum drying oven for drying to obtain the in-situ modified spherical ADN moisture-resistant composite material. The introduction of a modifier in this method ensures strong inter-structural forces and the hydrophobicity of the composite material.

Description

Technical Field

[0001] This invention relates to the field of explosives technology, specifically to an in-situ modified spherical ADN moisture-resistant composite material and its preparation method. Background Technology

[0002] Ammonium dinitramide (ADN) contains both oxidant and fuel components in its molecular structure, has a high oxygen content, and a heat of formation of -148.4 to -149.6 kJ / mol. It can be used as both an explosive and an oxidant in solid propellants. Unlike AP (heat of formation of -295.5 kJ / mol), a widely used oxidant in propellants, ADN does not contain chlorine in its molecular structure, and its combustion products produce no smoke, resulting in lower signal characteristics and less environmental pollution during missile launches. ADN can be used not only in intercontinental ballistic missile boosters but also in small-sized surface-to-air missiles, making it one of the most promising high-energy components of a new generation of solid propellants urgently needed for future strategic and tactical missiles. However, ADN is an ionic compound, formed by NH4+... + and N(NO2)2 - The composition of ADN is characterized by negative charges distributed throughout the crystal surface, making it highly susceptible to forming hydrogen bonds with water. It is also highly hygroscopic and incompatible with commonly used propellant binder systems, which severely restricts its practical application. Therefore, solving the hygroscopicity and compatibility with propellant components of ADN is a bottleneck technology for the large-scale application of ADN in composite explosives and solid propellants.

[0003] Currently, the main domestic and international technologies for reducing the hygroscopicity of ADN (Aqueous Dioxide) through spheroidization include emulsion spheroidization, spray spheroidization, jet milling spheroidization, ultrasonic-assisted spheroidization, micro-reaction spheroidization, and membrane emulsion crystallization. For example, FOI in Sweden has used ADN emulsion spheroidization technology since the 1990s to produce spherical ADN particles with a diameter of approximately 700 μm. ICT in Germany has also obtained spherical ADN particles through a melt-emulsion crystallization process, with an average particle size of 106 μm. A US company has used spray spheroidization technology to produce spherical particles of different sizes. ADN products exhibit high sphericity and uniformity. Swedish researchers have also used this technology to produce ADN with an average particle size of 50–250 μm. Roxel has used membrane emulsification crystallization technology to prepare ADN spherical particles with a narrow particle size distribution of 10–50 μm, and has achieved kilogram-level production capacity. Germany has used online XRD and other methods to obtain the influence of process parameters such as solvent type, melting temperature, and holding time on the continuous change of ADN crystal form during the sphericification process, and further optimized the sphericification process parameters. Although the hygroscopicity is improved after sphericification, it is difficult to reach the level of engineering application. Therefore, researchers further coated the surface of ADN on top of spheroidization in an attempt to reduce its hygroscopicity. For example, Thomas et al. used ethyl cellulose to coat cyclohexane using a liquid-phase separation method to obtain spherical ADN-coated particles with relatively complete coating layers; Ulrich et al. used cellulose acetate butyrate to microencapsulate ADN using a liquid-phase separation method to obtain structurally complete coated ADN; Jessica et al. used HTPB glue to microencapsulate spheroidized ADN, improving the compatibility between ADN and propellant components; Rahman et al. used ultrasonic treatment technology with polystyrene (PS) and HTPB as coating polymers to prepare microencapsulated ADN, reducing the hygroscopicity of ADN; the German ICT Institute used small fluidized bed technology and a granulation process of coating ADN with GAP. However, the above-mentioned re-coating still failed to achieve the desired effect, mainly because the interface between the coating material and the spherical ADN was poor, making it difficult to obtain a complete coating layer and resulting in poor hygroscopic resistance. Summary of the Invention

[0004] To address the aforementioned problems, the first objective of this invention is to provide a method for preparing an in-situ modified spherical ADN moisture-wicking composite material. This method innovatively introduces a modifier during the spheroidization process to obtain an in-situ modified spherical ADN moisture-wicking composite material. The active group at one end of the modifier reacts chemically with the ADN surface, while the inert group at the other end is hydrophobic. This not only results in strong interaction forces but also strong water shielding in the shielded environment.

[0005] The second objective of this invention is to provide an in-situ modified spherical ADN moisture-proof composite material. In this in-situ modified spherical ADN moisture-proof composite material, the active functional groups of the modifier act on the surface of the spherical ADN and expose hydrophobic functional groups. The surface of the composite material changes from hydrophilic to hydrophobic, and the moisture absorption is significantly reduced.

[0006] The first technical solution adopted in this invention is: a method for preparing an in-situ modified spherical ADN moisture-wicking composite material, comprising the following steps:

[0007] S1: Add crude ADN powder, modifier and emulsifier to the dispersion medium and stir to obtain ADN particle dispersion;

[0008] S2: Heat the ADN particle dispersion, stir and keep it warm to form a surface-modified ADN melt emulsion;

[0009] S3: Cool the surface-modified ADN molten emulsion liquid to cause the surface-modified ADN molten emulsion droplets to coalesce into spheres, thereby obtaining an in-situ modified spherical ADN moisture-absorbing composite material suspension;

[0010] S4: The in-situ modified spherical ADN moisture-proof composite material suspension is subjected to solid-liquid separation, and the solid is dried to obtain the in-situ modified spherical ADN moisture-proof composite material.

[0011] Preferably, the modifier comprises a hydrophobic group R and a reactive group P; the hydrophobic group R is one or more of a straight-chain or branched alkyl group containing 6 to 36 carbons, a straight-chain or branched fluoroalkyl group containing 6 to 36 carbons, and a phenyl or substituted phenyl group; the reactive group P is one or more of a primary amino group, a secondary amino group, and an isocyanate group.

[0012] Preferably, the modifier comprises one or more of octadecylamine, perfluorooctadecylamine, hexadecylamine, perfluorohexadecylamine, tetradecylamine, perfluorotetradecylamine, dodecylamine, perfluorododecylamine, octylamine, perfluorooctylamine, bis(octadecylamine), fluorobis(octadecylamine), bis(hexadecylamine), fluorobis(hexadecylamine), bis(tetradecylamine), fluorobis(tetradecylamine), bis(dodecylamine), fluorobis(dodecylamine), octadecyl isocyanate, fluorobis(octadecylamine), hexadecyl isocyanate, fluorohexadecyl isocyanate, tetradecyl isocyanate, fluorotetradecyl isocyanate, dodecyl isocyanate, fluorododecyl isocyanate, methylbenzylamine, and 2,4-difluorobenzylamine.

[0013] Preferably, the emulsifier is one or more of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, dodecyl betaine, octadecyl ammonium bromide, octadecyl trimethyl ammonium chloride, dodecyl dimethylamine oxide, Tween 20, Tween 80, Span 20, Span 60 and Span 80.

[0014] Preferably, the dispersion medium is one or more of paraffin oil, silicone oil, white oil, dioctyl sebacate, dioctyl adipate, transformer oil, and homopolymer glycidyl azide polymer.

[0015] Preferably, the mass ratio of the crude ADN powder to the dispersion medium is 0.1:2 to 3:10, the mass ratio of the modifier to the crude ADN powder is 0.001:1 to 0.1:1, and the mass ratio of the emulsifier to the crude ADN powder is 0.0001:1 to 0.01:1.

[0016] Preferably, step S1 includes: stirring at room temperature for 5 to 20 minutes to obtain an ADN particle dispersion.

[0017] Preferably, step S2 includes:

[0018] The ADN particle dispersion is heated to 92℃~96℃, stirred at a stirring speed of 300rpm-1000rpm and kept at the temperature for 20min~60min to form a surface-modified ADN melt emulsion.

[0019] Preferably, step S3 includes:

[0020] The surface-modified ADN melt emulsion is cooled to 0-20°C at a cooling rate of 10-50°C / min, causing the surface-modified ADN melt emulsion droplets to coalesce into spheres, thus obtaining an in-situ modified spherical ADN moisture-wicking composite material suspension.

[0021] The second technical solution adopted in this invention is: an in-situ modified spherical ADN moisture-wicking composite material prepared by the preparation method described in the first technical solution. The in-situ modified spherical ADN moisture-wicking composite material is spherical, with an ADN core and an outer layer being the reaction product of the modifier and ADN.

[0022] The beneficial effects of the above technical solution are as follows:

[0023] (1) The present invention discloses an innovative method for preparing an in-situ modified spherical ADN moisture-proof composite material by introducing a modifier during the spheroidization process to obtain an in-situ modified spherical ADN moisture-proof composite material. The active group at one end of the modifier reacts chemically with the surface of the ADN, while the inert group at the other end is hydrophobic. It not only has strong interaction force, but also strong water shielding effect in the shielding environment.

[0024] (2) The in-situ modified spherical ADN moisture-proof composite material disclosed in this invention has a compact structure, adjustable composition and modification amount, adjustable particle size and particle size distribution, low cost, strong versatility, and can achieve ideal moisture-proof effect with only a very small amount of modifier, making it easy to industrialize.

[0025] (3) The preparation method disclosed in this invention is simple, fast, safe and low cost. It is fast, one-step molding and has good reproducibility. The material structure and properties are adjustable and controllable, and it is suitable for industrial production. Moreover, the preparation method disclosed in this invention can be used to modify the spherical surface of ADN in situ, which not only ensures the strong interaction between structures, but also ensures the energy performance of the composite material.

[0026] (4) The in-situ modified spherical ADN moisture-proof composite material disclosed in this invention has low moisture absorption. Under the conditions of temperature of 25°C and relative humidity of 57%, the saturated moisture absorption rate is less than 0.1% or no moisture absorption (tested using GJB770A-97).

[0027] (5) The in-situ modified spherical ADN moisture-proof composite material disclosed in this invention is used for high-energy solid propellants to meet the performance requirements of high-energy solid propellants. This composite material has good application prospects in the fields of high-energy solid propellants, explosives, and pyrotechnics.

[0028] (6) This invention differs from conventional methods for reducing the hygroscopicity of ADN—the typical "two-step method" of first spherifying and then coating with organic (inorganic) small molecules or polymers, which suffers from unsatisfactory anti-hygroscopic effects or a severe decrease in energy (oxidant function). This invention adds crude ADN powder, modifier, and emulsifier together to a dispersion medium, heating and stirring simultaneously to melt the crude ADN powder. Under the action of the emulsifier and stirring, molten emulsion droplets are formed. After the droplet surface reacts with the modifier, the molten emulsion droplets are rapidly cooled and agglomerated into spheres, thereby obtaining an in-situ modified spherical ADN anti-hygroscopic composite material. The method disclosed in this invention utilizes the active groups of the modifier... The group bonds ADN with chemical interactions such as ionic and covalent bonds, which not only have strong interactions but also counteract the charge polarization effect on the crystal surface. On the other hand, the other end of the modifier of this invention is a hydrophobic group, which can not only prevent water molecules from diffusing to the ADN surface and improve the compatibility of ADN with isocyanate (-N=C=O), but also maintain the energy, performance and efficiency of ADN as an oxidant. Therefore, the method disclosed in this invention improves the conventional ADN anti-hygroscopic process: the typical "two-step process" of first spheroidizing and then coating has the disadvantages of unsatisfactory anti-hygroscopic effect or serious reduction in energy (oxidant function). The preparation process is simple, low-cost and the structural composition is adjustable and controllable. Attached Figure Description

[0029] Figure 1 The following are scanning electron microscope (SEM) images of (a) crude ADN and (b) in-situ modified spherical ADN moisture-resistant composite material provided for an embodiment of the present invention.

[0030] Figure 2(a) A schematic diagram of the contact angle between crude ADN and water and (b) a schematic diagram of the contact angle between in-situ modified spherical ADN moisture-absorbing composite material and water, provided for an embodiment of the present invention;

[0031] Figure 3 The total elemental EDS spectrum of the surface of the in-situ modified spherical ADN moisture-wicking composite material provided in one embodiment of the present invention;

[0032] Figure 4 The following are EDS spectra of (a) O element, (b) N element, (c) C element, and (d) K element of the in-situ modified spherical ADN moisture-wicking composite material provided in an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further illustrated below with specific embodiments. It should be noted that those skilled in the art can make several modifications and improvements without departing from the principle of the present invention, and these should also be considered to fall within the protection scope of the present invention.

[0034] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0035] This invention discloses a method for preparing an in-situ modified spherical ADN moisture-wicking composite material, comprising the following steps:

[0036] S1: Add crude ADN powder, modifier and emulsifier to the dispersion medium and stir at room temperature for 5 to 20 minutes to obtain ADN particle dispersion;

[0037] S2: Heat the ADN particle dispersion to 92℃~96℃, stir at a stirring speed of 300rpm-1000rpm and keep warm for 20min~60min to form a surface-modified ADN melt emulsion.

[0038] S3: Cool the surface-modified ADN melt emulsion to 0-20°C at a cooling rate of 10-50°C / min to cause the surface-modified ADN melt emulsion droplets to coalesce into spheres, thereby obtaining an in-situ modified spherical ADN moisture-absorbing composite material suspension.

[0039] S4: The in-situ modified spherical ADN moisture-proof composite material suspension is transferred to a vacuum filtration device for vacuum filtration to remove solvent and emulsifier and achieve solid-liquid separation; the filtrate can be recycled, and the solid is transferred to a vacuum drying oven at 50-60°C for 6-8 hours to obtain the in-situ modified spherical ADN moisture-proof composite material.

[0040] The mass ratio of the crude ADN powder to the dispersion medium is 0.1:2 to 3:10, meaning that the mass of the ADN accounts for 5% to 30% of the mass of the dispersion medium.

[0041] The mass ratio of the modifier to the crude ADN powder is 0.001:1 to 0.1:1, that is, the mass of the modifier accounts for 0.1% to 10% of the mass of the crude ADN powder; the modifier includes a hydrophobic group R and a reactive group P; the hydrophobic group R is one or more of a straight-chain or branched alkyl group containing 6 to 36 carbons, a straight-chain or branched fluoroalkyl group containing 6 to 36 carbons, and a phenyl or substituted phenyl group; the reactive group P is one or more of a primary amino group (-NH2), a secondary amino group (-NH-), and an isocyanate group (-NCO).

[0042] Modifiers include, for example, one or more of octadecylamine, perfluorooctadecylamine, hexadecylamine, perfluorohexadecylamine, tetradecylamine, perfluorotetradecylamine, dodecylamine, perfluorododecylamine, octylamine, perfluorooctylamine, bis(octadecylamine), fluorobis(octadecylamine), bis(hexadecylamine), fluorobis(hexadecylamine), bis(tetradecylamine), fluorobis(tetradecylamine), bis(dodecylamine), fluorobis(dodecylamine), octadecyl isocyanate, fluorobis(octadecylamine), hexadecyl isocyanate, fluorohexadecyl isocyanate, tetradecyl isocyanate, fluorotetradecyl isocyanate, dodecyl isocyanate, fluorododecyl isocyanate, methylbenzylamine, and 2,4-difluorobenzylamine.

[0043] The mass ratio of the emulsifier to the crude ADN powder is 0.0001:1 to 0.01:1, that is, the mass of the emulsifier accounts for 0.01% to 1% of the mass of the crude ADN powder; the emulsifier is one or more of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, dodecyl betaine, octadecyl ammonium bromide, octadecyl trimethylammonium chloride, dodecyl dimethylamine oxide, Tween 20, Tween 80, Span 20, Span 60 and Span 80.

[0044] The dispersion medium is one or more of the following: paraffin oil, silicone oil, white oil, dioctyl sebacate, dioctyl adipate, transformer oil, homopolymer glycidyl azide polymer, etc.

[0045] The present invention controls the mass of crude ADN powder to be 5-30% of the mass of the dispersion medium, the mass of the modifier to be 0.1%-10% of the mass of the crude ADN powder, and the mass of the emulsifier to be 0.01%-1% of the mass of the crude ADN powder, which is beneficial to pellet formation and maintaining a relative balance between energy and hygroscopicity.

[0046] Furthermore, the above-mentioned method for preparing in-situ modified spherical ADN moisture-wicking composite material can yield an in-situ modified spherical ADN moisture-wicking composite material. This in-situ modified spherical ADN moisture-wicking composite material is spherical, with an ADN core and an outer layer consisting of the reaction product of the modifier and ADN. In-situ chemical bonding and physical interaction occur between the modifier and the spherical ADN, and the particle surface is hydrophobic. The chemical bonding includes ionic and covalent bonds; the physical interaction includes hydrogen bonds.

[0047] Example 1

[0048] 10g of crude ADN powder, 0.1g of octadecylamine, and 0.02g of octadecylammonium bromide were dispersed in a three-necked flask containing 500g of paraffin oil and kept suspended by stirring at 500rpm to form an ADN particle dispersion. The ADN particle dispersion was heated to 95℃, stirred at 300rpm, and kept at this temperature for 30min to form a surface-modified ADN melt emulsion. The surface-modified ADN melt emulsion was rapidly cooled to 20℃ at a cooling rate of 10℃ / min to obtain an in-situ modified spherical ADN moisture-absorbing composite material suspension. Solid-liquid separation was achieved by vacuum filtration, and the liquid was recovered and reused. The solid powder was kept at 50℃ and -0.1MP for 8h to obtain a light gray in-situ modified spherical ADN moisture-absorbing composite material, denoted as PADN-01.

[0049] Equal amounts of PADN-01 obtained in Example 1, spherical ADN, and crude ADN were placed under conditions of 25°C and 57% relative humidity for hygroscopicity testing. The results showed that the saturated hygroscopicity of PADN-01 was 0, the 24-hour moisture absorption weight gain of spherical ADN was 1.52%, and the saturated hygroscopicity (15 days) was 2.95%, while the 24-hour moisture absorption weight gain of crude ADN was 2.58%, and the saturated hygroscopicity (15 days) was 7.47%. Figure 1 As shown, the in-situ modified spherical ADN moisture-wicking composite material (PADN-01) is spherical, while the coarse ADN is rod-shaped or needle-shaped; as Figure 2 As shown, PADN-01 is hydrophobic, while crude ADN is hydrophilic. The contact angle between PADN-01 and water is greater than 90°, while the contact angle between crude ADN and water is less than 10°. Figure 3 and Figure 4 It can be seen that the C element is relatively uniformly distributed on the surface of the composite material, indicating that the outermost layer is a carbon-containing modifier, and that the modifier is on the surface of the spherical ADN. Figure 4 The O, N, and K element EDS spectra further demonstrate that the modifier is modified on the spherical ADN surface, and has a significant effect on... Figure 3 To provide supplementary explanations of the macroscopic phenomena.

[0050] Example 2

[0051] 20g of crude ADN powder, 0.2g of dioctadecylamine, and 0.01g of sodium dodecyl sulfonate were dispersed in a three-necked flask containing 600g of silicone oil and kept suspended by stirring at 450rpm to form an ADN particle dispersion. The ADN particle dispersion was heated to 96℃, stirred at 500rpm, and kept at this temperature for 40min to form a surface-modified ADN melt emulsion. The surface-modified ADN melt emulsion was rapidly cooled to 0℃ at a cooling rate of 20℃ / min to obtain an in-situ modified spherical ADN moisture-absorbing composite material suspension. Solid-liquid separation was achieved by vacuum filtration, and the liquid was recovered and reused. The solid powder was kept at 50℃ and -0.1MP for 8h to obtain a deep yellow in-situ modified spherical ADN moisture-absorbing composite material, denoted as PADN-02.

[0052] Equal amounts of PADN-02 obtained in Example 2, spherical ADN, and crude ADN were placed under conditions of 25°C and 57% relative humidity for hygroscopicity testing. The results showed that the saturated hygroscopicity of PADN-01 was 0.03%, the 24-hour hygroscopic weight gain of spherical ADN was 1.72%, and the saturated hygroscopicity (15 days) was 3.25%, while the 24-hour hygroscopic weight gain of crude ADN was 2.58%, and the saturated hygroscopicity (15 days) was 7.47%.

[0053] Example 3

[0054] 10g of crude ADN powder, 0.2g of perfluorooctyl primary amine, and 0.01g of Tween 20 were dispersed in a three-necked flask containing 500g of dioctyl sebacate and kept suspended by stirring at 400rpm to form an ADN particle dispersion. The ADN particle dispersion was heated to 94℃, stirred at 1000rpm, and kept at this temperature for 60min to form a surface-modified ADN melt emulsion. The surface-modified ADN melt emulsion was rapidly cooled to 0℃ at a cooling rate of 20℃ / min to obtain an in-situ modified spherical ADN moisture-wicking composite material suspension. Solid-liquid separation was achieved by vacuum filtration, and the liquid was recovered and reused. The solid powder was kept at 60℃ and -0.1MP for 6h to obtain a light yellow in-situ modified spherical ADN moisture-wicking composite material, denoted as PADN-03.

[0055] Equal amounts of PADN-03 obtained in Example 3, spherical ADN, and crude ADN were placed under conditions of 25°C and 57% relative humidity for hygroscopicity testing. The results showed that the saturated hygroscopicity of PADN-03 was 0.01%, the 24-hour hygroscopic weight gain of spherical ADN was 1.32%, and the saturated hygroscopicity (15 days) was 2.88%, while the 24-hour hygroscopic weight gain of crude ADN was 2.58%, and the saturated hygroscopicity (15 days) was 7.47%.

[0056] Example 4

[0057] 10g of crude ADN powder, 0.4g of octadecyl isocyanate, and 0.02g of Span 60 were dispersed in a three-necked flask containing 400g of transformer oil and kept suspended by stirring at 500rpm to form an ADN particle dispersion. The ADN particle dispersion was heated to 96℃, stirred at 800rpm, and kept at this temperature for 20min to form a surface-modified ADN melt emulsion. The surface-modified ADN melt emulsion was rapidly cooled to 20℃ at a cooling rate of 20℃ / min to obtain an in-situ modified spherical ADN moisture-absorbing composite material suspension. Solid-liquid separation was achieved by vacuum filtration, and the liquid was recovered and reused. The solid powder was kept at 50℃ and -0.1MP for 8h to obtain a deep yellow in-situ modified spherical ADN moisture-absorbing composite material, denoted as PADN-04.

[0058] Equal amounts of PADN-04 obtained in Example 4, spheroidized ADN, and crude ADN were placed under conditions of 25°C and 57% relative humidity for hygroscopicity testing. The results showed that the saturated hygroscopicity of PADN-04 was 0, the 24-hour hygroscopic weight gain of spheroidized ADN was 1.12%, and the saturated hygroscopicity (15 days) was 2.65%, while the 24-hour hygroscopic weight gain of crude ADN was 2.58%, and the saturated hygroscopicity (15 days) was 7.47%.

[0059] Example 5

[0060] 15g of crude ADN powder, 0.2g of 2,4-difluorobenzylamine, and 0.02g of dodecyl dimethylamine oxide were dispersed in a three-necked flask containing 400g of transformer oil and kept suspended by stirring at 500rpm to form an ADN particle dispersion. The ADN particle dispersion was heated to 92℃, stirred at 400rpm, and kept at this temperature for 60min to form a surface-modified ADN melt emulsion. The surface-modified ADN melt emulsion was rapidly cooled to 20℃ at a cooling rate of 10℃ / min to obtain an in-situ modified spherical ADN moisture-absorbing composite material suspension. Solid-liquid separation was achieved by vacuum filtration, and the liquid was recovered and reused. The solid powder was kept at 50℃ and -0.1MP for 8h to obtain a yellowish-brown in-situ modified spherical ADN moisture-absorbing composite material, denoted as PADN-05.

[0061] Equal amounts of PADN-05 obtained in Example 5, spherical ADN, and crude ADN were placed under conditions of 25°C and 57% relative humidity for hygroscopicity testing. The results showed that the saturated hygroscopicity of PADN-05 was 0.08%, the 24-hour hygroscopic weight gain of spherical ADN was 1.15%, and the saturated hygroscopicity (15 days) was 2.85%, while the 24-hour hygroscopic weight gain of crude ADN was 2.58%, and the saturated hygroscopicity (15 days) was 7.47%.

[0062] Comparative Example 1

[0063] Referring to the method in the published literature "Research on Spherical Ammonium Dinitramide" (Solid Rocket Technology, 2002, 1, 29-32), spherical products were prepared using the ADN melt spheroidization technique. Under the conditions of 35℃ and 75% relative humidity, the crude ADN product turned into an aqueous solution after 6 hours, and the moisture absorption rate of the spherical product after 96 hours was 1.99%.

[0064] Comparative Example 2

[0065] Following the method described in the published paper, "Construction of ammonium dinitramide@monoaminopropylheptaphenylsilsesquioxane core-shell energetic microspheres with enhanced hygroscopicity inhibition and thermal decomposition properties" (Materials Chemistry and Physics, 2023, 303, 127822), spherical products coated with POSS-NH2 were prepared by coating spherical ADN particles with POSS-NH2. Under conditions of 20°C and 50%–60% relative humidity, the moisture absorption rate of the spherical products coated with POSS-NH2 was measured to be 5–15%.

[0066] According to the experimental data in Examples 1 to 5, the in-situ modified spherical ADN moisture-wicking composite material prepared by the present invention has excellent performance. At the same time, compared with the technical solutions of only spheroidization and secondary coating after spheroidization shown in Comparative Examples 1 and 2, the moisture-wicking effect of the in-situ modified spherical ADN moisture-wicking composite material prepared by the present invention is greatly improved.

[0067] This invention discloses a method for preparing an in-situ modified spherical ADN anti-hygroscopic composite material. This method integrates in-situ emulsion spheroidization and surface modification, resulting in a simple process, low cost, controllable coating amount, and adjustable particle size. More importantly, this invention employs a one-step method to perform ADN spheroidization and surface modification. On one hand, ADN spheroidization reduces the specific surface area and surface energy; on the other hand, the active functional groups of the modifier coordinate with ADN via ionic (covalent) bonds, resulting in strong interactions and the ability to counteract the charge polarization of the crystal surface. Simultaneously, the modifier's hydrophobicity not only prevents water molecules from diffusing to the ADN surface, reducing hygroscopicity, but also improves its compatibility with isocyanates (-N=C=O), thereby maintaining its energy performance and combustion efficiency as a high-energy oxidant. This method is suitable for the preparation and production of in-situ modified ADN spheroidized anti-hygroscopic composite materials, and the results can be applied to the development of novel high-energy, green, and insensitive solid propellants.

[0068] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments; the above descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present invention without departing from the spirit and scope of the present invention, and all such modifications and improvements fall within the scope of the present invention; the scope of protection of the present invention is determined by the appended claims.

Claims

1. A method for preparing an in-situ modified spherical ADN moisture-wicking composite material, characterized in that, Includes the following steps: S1: Add crude ADN powder, a modifier, and an emulsifier to a dispersion medium and stir to obtain an ADN particle dispersion; the modifier includes one or more of perfluorooctadecylamine, hexadecylamine, perfluorohexadecylamine, tetradecylamine, perfluorotetradecylamine, dodecylamine, perfluorododecylamine, octylamine, perfluorooctylamine, bis(octadecylamine), fluorobis(octadecylamine), bis(hexadecylamine), fluorobis(hexadecylamine), bis(tetradecylamine), fluorobis(tetradecylamine), bis(dodecylamine), fluorobis(dodecylamine), octadecyl isocyanate, fluorobis(octadecylamine), hexadecyl isocyanate, fluorohexadecyl isocyanate, tetradecyl isocyanate, fluorotetradecyl isocyanate, dodecyl isocyanate, fluorododecyl isocyanate, methylbenzylamine, and 2,4-difluorobenzylamine; the mass ratio of the modifier to the crude ADN powder is 0.001:1 to 0.1:1; S2: Heat the ADN particle dispersion, stir and keep it warm to form a surface-modified ADN melt emulsion; S3: Cool the surface-modified ADN molten emulsion liquid to cause the surface-modified ADN molten emulsion droplets to coalesce into spheres, thereby obtaining an in-situ modified spherical ADN moisture-absorbing composite material suspension; S4: The in-situ modified spherical ADN moisture-proof composite material suspension is subjected to solid-liquid separation, and the solid is dried to obtain the in-situ modified spherical ADN moisture-proof composite material.

2. The preparation method according to claim 1, characterized in that, The emulsifier is one or more of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, dodecyl betaine, octadecyl ammonium bromide, octadecyl trimethyl ammonium chloride, dodecyl dimethylamine oxide, Tween 20, Tween 80, Span 20, Span 60 and Span 80.

3. The preparation method according to claim 1, characterized in that, The dispersion medium is one or more of the following: paraffin oil, silicone oil, white oil, dioctyl sebacate, dioctyl adipate, transformer oil, and homopolymer glycidyl azide polymer.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the crude ADN powder to the dispersion medium is 0.1:2 to 3:10, and the mass ratio of the emulsifier to the crude ADN powder is 0.0001:1 to 0.01:

1.

5. The preparation method according to claim 1, characterized in that, Step S1 includes: stirring at room temperature for 5 to 20 minutes to obtain an ADN particle dispersion.

6. The preparation method according to claim 1, characterized in that, Step S2 includes: The ADN particle dispersion is heated to 92℃~96℃, stirred at a stirring speed of 300rpm-1000rpm and kept at the temperature for 20min~60min to form a surface-modified ADN melt emulsion.

7. The preparation method according to claim 1, characterized in that, Step S3 includes: The surface-modified ADN melt emulsion is cooled to 0-20°C at a cooling rate of 10-50°C / min, causing the surface-modified ADN melt emulsion droplets to coalesce into spheres, thus obtaining an in-situ modified spherical ADN moisture-wicking composite material suspension.

8. An in-situ modified spherical ADN moisture-wicking composite material prepared by the preparation method according to any one of claims 1-7, characterized in that, The in-situ modified spherical ADN moisture-wicking composite material is spherical, with an ADN core and an outer layer consisting of the reaction product of the modifier and ADN.

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