High-strength energetic compound based on polydopamine and thiourea polymer and preparation method

Abstract

The invention discloses a high-strength energetic compound based on a polydopamine and thiourea polymer and a preparation method of the high-strength energetic compound, and the energetic compound is composed of energetic crystal 1, 3, 5-triamino-2, 4, 6-trinitrobenzene, the polydopamine and the thiourea polymer. The preparation method comprises the following steps: modifying an energetic crystal 1, 3, 5-triamino-2, 4, 6-trinitrobenzene through polydopamine in advance; the polythiourea is obtained through reaction of 2, 2 '-(ethylene dioxygen) diethylamine, carbon disulfide and trimethylolpropane tripolypropylene glycol ether, and the addition amount is 2.5 wt.%-10 wt.%; and mixing the two components by a kneading method, and drying to obtain the energetic compound. The obtained compound has the characteristics of strengthening and toughening, the Brazil mechanical strength reaches 14.76 MPa, and the fracture strain reaches 0.474%. By introducing polyphenol polydopamine and polythiourea to achieve a synergistic effect, the mechanical property of the explosive is greatly improved, and a technical support can be provided for the application of the explosive; meanwhile, the preparation method is simple, mild in reaction condition and easy for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of novel energetic composites, and particularly relates to a high-strength energetic composite based on polydopamine and thiourea polymer and a preparation method thereof. Background Art

[0002] Energetic composites generally consist of single-component explosives, binders, and functional additives, ensuring their good processing, safety, mechanical, and detonation properties. 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) is currently the only insensitive high-energy single-component explosive certified by eleven safety tests of the US Department of Energy. The pressed PBX based on TATB has the characteristics of being insensitive, high-energy, and low-vulnerability, and is widely used in various weapon charges. In energetic composites, although the binder accounts for a small proportion, it makes an important contribution to the processability and mechanical properties of the explosive. Fluoropolymers have the advantages of high density, good stability, and aging resistance, and are a widely used binder system [Central European Journal of Energetic Materials, 2020, 17(3): 428-450; Journal of Energetic Materials, 2023, 2023(1): 1-21]. However, the interfacial interaction between fluoropolymers and TATB crystals is weak, resulting in incomplete wetting and spreading during the coating process, which affects the practical application of energetic composites [J. Colloid. Interf. Sci., 2010, 352, 535-541]. Enhancing the interfacial interaction between the binder and the explosive can effectively improve the mechanical properties of energetic composites. For example, Zheng et al. reported grafting neutral polymers on the surface of TATB to construct a polymer brush structure, and the mechanical properties of the composite were improved by about 24% [Surfaces and Interfaces, 2024, 52, 104896]. There is a literature report on a mixed explosive with high-density hydrogen bond interactions, which enhances the interfacial strength through the interaction between multiple hydrogen bond molecules and the binder and the explosive [Energetic Materials Frontiers 2024, 5, 121-130].

[0003] On the other hand, by modifying the binder system, better adhesion ability and interaction with explosives can be obtained. Some studies have found that when using binders with higher strength and glass transition temperature (Tg) in explosives, the mechanical strength and creep resistance of the explosives are enhanced [RSC Advances, 2015, 5(39): 30592-30601]. However, too high Tg may make the material processing performance worse and even lead to a decrease in the toughness of the composite explosive. By introducing covalent bonds (such as disulfide bonds, Diels-Alder reactions, and acylhydrazone bonds) and supramolecular non-covalent bonds (such as hydrogen bonds, metal coordination bonds, hydrophobic interactions, host-guest interactions, and π-π stacking) into the polymer binder molecular chain, the binder can have dynamic properties, achieve self-healing under certain conditions, extend the service life of the binder, and can in-situ repair damages such as microcracks generated inside the polymer matrix composite, thereby improving safety and mechanical properties. Li Zijian et al. introduced thiourea polymers as binders in explosives. Compared with traditional fluorine-containing binders, the Brazilian strength and elongation rate were significantly improved [CN1116211011A; Energetic Materials Frontiers, 2023, 4(2): 85-92]. However, the method used N,N'-thiocarbonyl diimidazole as a condensing agent, which is expensive and the by-products are difficult to remove, not conducive to large-scale synthesis; at the same time, the obtained composite explosive has insufficient creep resistance. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-strength energetic composite based on polydopamine and thiourea polymer and its preparation method, which is used to enhance the interfacial interaction of the composite material and solve the technical problem of poor mechanical properties. The core of the present invention is to utilize the synergistic effect of polydopamine and cross-linked thiourea in explosives to obtain an energetic composite with significantly enhanced mechanical strength and toughness.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A high-strength energetic composite based on polydopamine and thiourea polymer, comprising: insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene with a particle size of 5-50 μm;

[0007] Polydopamine, formed by the self-polymerization of dopamine hydrochloride in a buffer solution with a pH of 8-8.5 and coated on the surface of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene;

[0008] Polythiourea, copolymerized from 2,2'-(ethylenedioxy)bisethylamine, carbon disulfide, and trimethylolpropane tripropyleneglycol ether, with a molecular weight of (10-50) kg / mol, a cross-linking degree of 2%-10%, and a mass ratio in the composite of (2.5-10) wt.%.

[0009] The high-strength energetic composite of polydopamine and thiourea polymer in this application utilizes the self-polymerization of polyphenol monomers to form a cross-linked network, forms a strong hydrogen bond cross-linked network between thiourea polymers, introduces a covalent cross-linked structure in the interfacial constraint layer, and introduces a strong hydrogen bond non-covalent cross-linked structure in the bonding layer.

[0010] This invention also provides a preparation method of a high-strength energetic composite based on polydopamine and polythiourea, including the following steps:

[0011] (1) Surface pretreatment: Adjust the pH of the buffer aqueous solution to (8 - 8.5) with dilute hydrochloric acid, add 1,3,5-triamino-2,4,6-trinitrobenzene explosive monomer and disperse it evenly, add dopamine hydrochloride, stir, filter by suction, and dry in vacuum to obtain the pretreated powder;

[0012] (2) Preparation of polythiourea solution: Add a certain amount of polythiourea to the dichloromethane / ethanol mixed solution, stir until the solid is completely dissolved to obtain a polythiourea solution with a certain concentration;

[0013] (3) Preparation of energetic composite: Add the pretreated powder obtained in step (1) to the solvent, heat and stir to form a mixed suspension, then add a certain amount of the polythiourea solution obtained in step (2), stir and mix, perform vacuum treatment, and heat and dry to obtain the composite explosive.

[0014] In step (1), the addition amount of dopamine hydrochloride is in a mass ratio of (1 / 200 - 1 / 50) to the mass of TATB, and the dopamine concentration in the buffer solution is (1 - 2) g / L, and the vacuum degree is (0.02 - 0.08) MPa.

[0015] In step (2), the ethanol / dichloromethane solvent ratio is 1 / 20 - 1 / 5, and the mass ratio of polythiourea to the solvent is (4 - 8) wt.%.

[0016] The heating temperature in step (2) is (40 - 70) °C, the stirring speed is (400 - 800) rpm, and the solvent is one of dichloromethane, ethyl acetate, and butyl acetate.

[0017] The beneficial effects brought by the high-strength energetic composite based on polydopamine and thiourea polymer and its preparation method disclosed in this application include but are not limited to:

[0018] The composite obtained by the present invention has the characteristics of strengthening and toughening. Its Brazilian mechanical strength reaches 14.76 MPa, the highest compressive fracture strength is 48.5 MPa, and the fracture strain reaches 0.474%. By introducing the synergistic effect of polyphenolic polydopamine and polythiourea, a significant improvement in the mechanical properties of the explosive is achieved, which can provide technical support for the application of the explosive. At the same time, the preparation method is simple, the reaction conditions are mild, and it is easy to scale up production. Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the structure of the energetic composite in the present invention;

[0020] Figure 2 It is a physical diagram of crosslinked polythiourea in the present invention;

[0021] Figure 3 It is a physical diagram of the mechanical test piece of the energetic composite in the present invention. Detailed Embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] On the contrary, the present application covers any alternatives, modifications, equivalent methods and solutions made within the spirit and scope of the present application defined by the claims. Further, in order to enable the public to have a better understanding of the present application, some specific details are described in detail in the following detailed description of the present application. Those skilled in the art can fully understand the present application without the description of these details.

[0024] The following will detail an energetic composite with high strength based on polydopamine and thiourea polymer and its preparation method involved in the embodiments of the present application.

[0025] Examples 1-3 are preparation methods of energetic composites with high strength based on polydopamine and thiourea polymer; Example 4 is a control group, a preparation method of an energetic composite obtained by bonding with crosslinked polythiourea; Example 5 is a control group, a preparation method of an energetic composite obtained by bonding with uncrosslinked polythiourea. Example 6 is a blank group, an energetic composite obtained by using a fluoropolymer as a binder.

[0026] Example 1

[0027] As Figure 1As shown, after adding 2.6 g of buffer into 2 L of pure water and stirring, dilute hydrochloric acid was added dropwise to adjust the pH value to 8.5. Then 100 g of 1,3,5-triamino-2,4,6-trinitrobenzene explosive powder was added, and the explosive crystals were dispersed at a rotation speed of 600 rpm. Subsequently, 4 g of dopamine hydrochloride was added and waited until it was completely dissolved. After continuing to stir for 6 h, filtration, washing, and vacuum drying were carried out to obtain the pretreated explosive. Through component analysis, the content of 1,3,5-triamino-2,4,6-trinitrobenzene in the pretreated explosive was about 99.6%. As Figure 1 shown.

[0028] 6 g of polythiourea with a molecular weight of 25.6 kg / mol (crosslinking degree of 5%) was put into 94 g of mixed solvent (ethanol / dichloromethane = 1 / 20), and stirred at 450 rpm for a certain time until all the solids were dissolved to obtain a pale orange polythiourea solution with a concentration of 6 wt.%.

[0029] 47.7 g of the above explosive (ensuring a solid content of 95%) was mixed with ethyl acetate, and the whole was treated in a 60°C water bath. Stirred at a rotation speed of (500 - 600) rpm, 62.5 g of polythiourea solution was added dropwise, and vacuum treatment was carried out. As the solvent continued to volatilize, the suspension gradually adhered and formed particles. When the material was not completely dry, it was taken out and put into an aluminum tray and dried at 60°C to obtain the shaped powder of the energetic composite explosive (total amount about 50 g). See Figure 2 Figure (a) in the attached drawings.

[0030] As Figure 3 shown, after weighing a certain amount of shaped powder and preheating it at 120°C, cylindrical charges with Φ20 mm×6 mm and Φ20 mm×20 mm were pressed at a pressure of 110 kN. The Brazilian strength (indirect tension) of the former was 14.76 MPa, and the fracture strain was 0.474%; the compressive strength of the latter was 48.5 MPa, and the compressive fracture strain was 3.01%.

[0031] Example 2

[0032] After adding 2.6 g of buffer into 2 L of pure water, dilute hydrochloric acid was added dropwise to adjust the pH value to 8.3. Then 100 g of 1,3,5-triamino-2,4,6-trinitrobenzene explosive powder was added, and the explosive crystals were dispersed at a rotation speed of 650 rpm. Subsequently, 4 g of dopamine hydrochloride was added, and after continuing to stir for 6 h, filtration, washing, and vacuum drying were carried out to obtain the pretreated explosive. Through component analysis, the content of 1,3,5-triamino-2,4,6-trinitrobenzene in the pretreated explosive was about 99.5%.

[0033] Take 48.99 g of the above explosive (ensuring a solid content of 97.5%) and mix it with ethyl acetate. Treat the whole in a 60°C water bath. Stir at a speed of (550 - 650) rpm, and gradually add dropwise 20.83 g of the polythiourea solution in Example 1. Conduct vacuum treatment. As the solvent continuously volatilizes, the suspension gradually agglomerates into particles. When the material is not completely dry, take it out and place it in an aluminum tray, and dry it at 60°C to obtain the shaped powder of the energetic composite explosive (total amount is about 50 g).

[0034] Weigh a certain amount of shaped powder, preheat it at 120°C, and then press it into a Φ20 mm × 6 mm under a pressure of 110 kN. The measured Brazilian strength is 10.59 MPa, and the fracture strain is 0.144%. After pressing it into a Φ20 mm × 20 mm explosive column, the measured compressive strength is 43.1 MPa, and the compressive fracture strain is 3.62%.

[0035] Comparing with Example 1, it can be seen that increasing the content of the explosive will significantly reduce the mechanical properties of the energetic composite. The main reason is that the content of the binder becomes less, and some explosive crystals are not completely coated by the binder, resulting in poor interfacial interaction and reduced mechanical properties.

[0036] Example 3

[0037] Adjust the pH value of 1 L of buffered aqueous solution to 8.5 with dilute hydrochloric acid, add 100 g of the single explosive 1,3,5-triamino-2,4,6-trinitrobenzene, add 2 g of dopamine hydrochloride, and conduct mechanical stirring at 450 rpm for 6 h. Then, conduct suction filtration, washing, and vacuum drying to obtain the pretreated explosive.

[0038] Take 4 g of polythiourea with a molecular weight of 27.1 kg / mol (crosslinking degree is 2%) and put it into 96 g of mixed solvent (ethanol / dichloromethane = 1 / 10). Stir at 400 rpm for a certain time. After complete dissolution, obtain a 4 wt.% polythiourea solution.

[0039] Take 47.7 g of the above explosive (ensuring a solid content of 95%) and mix it with butyl acetate. Place the whole in a 70°C water bath. Stir at a speed of (500 - 600) rpm, and gradually add dropwise 62.5 g of the 4% polythiourea solution in total amount. Conduct vacuum treatment. As the solvent continuously volatilizes, the suspension gradually agglomerates into particles. When the material becomes large particle powder, take it out and place it in an aluminum tray, and dry it at 70°C to obtain the shaped powder of the energetic composite explosive (total amount is about 50 g). See Figure 2 Figure (b) in

[0040] A certain amount of shaped powder was weighed, preheated at 120 °C, and then pressed into a Φ20mm×6mm sample under a pressure of 110 kN. The measured Brazilian strength was 12.98 MPa, and the fracture strain was 0.41%. After pressing into a Φ20mm×20mm charge, the measured compressive strength was 47.79 MPa, and the compressive fracture strain was 3.488%.

[0041] By comparison, in Example 1, polythiourea with a higher crosslinking degree was used as the binder. There are more contact interfaces between the binder network and the explosive crystals and polydopamine, and the interaction is stronger. Therefore, both the Brazilian and compressive strengths of Example 1 are better than those in this example.

[0042] Example 4

[0043] 4 g of polythiourea with a molecular weight of 25.6 kg / mol (crosslinking degree of 2%) was placed in 96 g of a mixed solvent (ethanol / dichloromethane = 1 / 10), and stirred at 400 rpm for a certain time. After complete dissolution, a 4 wt.% polythiourea solution was obtained.

[0044] 47.5 g of unmodified 1,3,5-triamino-2,4,6-trinitrobenzene explosive and dichloromethane were mixed, and the whole was placed in a 40 °C water bath. When stirring at a speed of (500 - 600) rpm, 62.5 g of 4% polythiourea solution was added dropwise. Through vacuum treatment, the solvent was volatilized, and the materials were gradually bonded and dried. Then, it was taken out and dried at 50 °C to obtain the shaped powder of the energetic composite explosive (total amount about 50 g).

[0045] A certain amount of shaped powder was weighed, preheated at 120 °C, and then pressed into a Φ20mm×6mm sample under a pressure of 110 kN. The measured Brazilian strength was 10.47 MPa, and the fracture strain was 0.335%. After pressing into a Φ20mm×20mm charge, the measured compressive strength was 36.35 MPa, and the compressive fracture strain was 3.53%.

[0046] By comparison, in this example, polydopamine was not used for surface pretreatment of the explosive, and only the same polythiourea as in Example 1 was used as the binder. Due to the lack of an explosive interface crosslinking layer, the hydrogen bond interaction with the binder was weakened, and the mechanical strength of the obtained energetic composite decreased significantly. Both the Brazilian and compressive strengths were lower than those in Example 1.

[0047] Example 5

[0048] 6 g of polythiourea with a molecular weight of 29.5 kg / mol (without adding trimethylolpropane tripropylene glycol ether as a crosslinking agent) was placed in 94 g of a mixed solvent (ethanol / dichloromethane = 1 / 15), and stirred at 500 rpm for a certain time. After complete dissolution, a 6 wt.% polythiourea solution was obtained.

[0049] Mix 47.5 g of untreated 1,3,5-triamino-2,4,6-trinitrobenzene explosive with ethyl acetate and place the whole in a 55 °C water bath. While stirring at a speed of (500 - 650) rpm, gradually add dropwise 41.7 g of a 6% polythiourea solution. Perform vacuum treatment to promote solvent evaporation. The material gradually adheres and dries. Take it out and dry it at 60 °C to obtain the shaped powder of the energetic composite explosive (total amount is about 50 g).

[0050] After preheating a certain amount of the shaped powder at 120 °C, press it into a Φ20 mm × 6 mm at a pressure of 110 kN. The measured Brazilian strength is 8.86 MPa and the fracture strain is 0.21%. After pressing it into a Φ20 mm × 20 mm explosive column, the measured compressive strength is 35.28 MPa and the compressive fracture strain is 3.05%.

[0051] By comparison, in this example, polydopamine was not used for surface pretreatment of the explosive, and an uncrosslinked polythiourea binder was used. Due to the lack of an explosive interface crosslinked layer, the hydrogen bond interaction with the binder is weakened; at the same time, the binder lacks the synergistic effect of physical and chemical crosslinking of hydrogen bonds. Therefore, the Brazilian and compressive strengths in this example are lower than those in Example 1 and Example 4.

[0052] Example 6

[0053] This example is a blank control example. Mix 47.5 g of untreated 1,3,5-triamino-2,4,6-trinitrobenzene with butyl acetate and stir to form a suspension in a 70 °C water bath at a speed of 650 rpm; slowly add dropwise about 31.25 g of an 8% fluorine-containing binder solution (copolymer of vinylidene fluoride and chlorotrifluoroethylene) of the binder. Perform vacuum treatment and stirring to make the suspension agglomerate into particles, and dry it at 70 °C to obtain the energetic composite.

[0054] Press the above energetic composite into a Φ20 mm × 6 mm explosive column at 110 °C and 120 KN pressure. The Brazilian fracture strength is 6.75 MPa and the Brazilian fracture strain is 0.197%; press it into a Φ20 mm × 20 mm explosive column, and the compressive fracture strength is 27.57 MPa and the compressive fracture strain is 2.93%.

[0055] By comparison, it can be seen that, under the condition of ensuring that the solid content of 1,3,5-triamino-2,4,6-trinitrobenzene in the composite is consistent, the compression fracture strength and Brazilian fracture strength of the explosive column obtained in Examples 1 and 3-5 are better than those in this example. Therefore, the introduction of polydopamine pretreatment to form a cross-linked interface layer on the surface of the explosive enhances the interface effect with the polymer binder compared to the untreated explosive, thereby improving the mechanical strength. On the other hand, the use of polythiourea binder and the introduction of a strong hydrogen bond non-covalent cross-linked structure in the mixed explosive can further enhance the hydrogen bonding effect with the cross-linked interface layer on the surface of the explosive, while enhancing the strength of the mixed explosive matrix, and ultimately achieving a significant improvement in the mechanics of the composite.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-strength energetic composite based on polydopamine and thiourea polymer, characterized in that: include: Insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene, particle size 5-50μm; Polydopamine, formed by self-polymerization of dopamine hydrochloride in a buffer solution of pH 8-8.5, and coated on the surface of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene; Polythiourea is prepared by copolymerization of 2,2'-(ethylenedioxy)diethylamine, carbon disulfide and trimethylolpropane tripropylene glycol ether, has a molecular weight of (10-50) kg / mol, a crosslinking degree of 2%-10%, and accounts for (2.5-10) wt.% of the mass in the composite.

2. The energetic composite according to claim 1, characterized in that: The high-strength energetic composite of polydopamine and thiourea polymer utilizes polyphenol monomers to self-polymerize to form a crosslinked network, a strong hydrogen bond crosslinked network is formed between thiourea polymers, a covalent crosslinked structure is introduced into the interface constraint layer, and a strong hydrogen bond non-covalent crosslinked structure is introduced into the bonding layer.

3. A method for preparing a high-strength energetic composite based on polydopamine and polythiourea, characterized in that: The following steps are involved: (1) Surface pretreatment: Use dilute hydrochloric acid to adjust the pH of the buffer solution to (8-8.5), add 1,3,5-triamino-2,4,6-trinitrobenzene explosive monomer to disperse evenly, add dopamine hydrochloride, stir, filter, and vacuum dry to obtain a pretreated powder; (2) Preparation of polythiourea solution: Add a certain amount of polythiourea to a dichloromethane / ethanol mixed solution and stir until the solid is completely dissolved to obtain a polythiourea solution with a certain concentration; (3) Preparation of energetic composite: the pre-treated powder obtained in step (1) is added to a solvent, heated and stirred to form a mixed suspension, and then a certain amount of the polythiourea solution obtained in step (2) is added, stirred and mixed, vacuum treated, heated and dried to obtain a composite explosive.

4. The method for preparing a high-strength energetic composite based on polydopamine and thiourea polymer according to claim 3, characterized in that: In step (1), the added amount of dopamine hydrochloride is a mass ratio of (1 / 200-1 / 50) to the mass of TATB, the dopamine concentration in the buffer solution is (1-2) g / L, and the vacuum degree is (0.02-0.08) MPa.

5. The method for preparing a high-strength energetic composite based on polydopamine and thiourea polymer according to claim 3, characterized in that: In step (2), the ethanol / dichloromethane solvent ratio is 1 / 20-1 / 5, and the mass ratio of polythiourea to solvent is (4-8) wt.%.

6. The method for preparing a high-strength energetic composite based on polydopamine and thiourea polymer according to claim 3, characterized in that: The heating temperature in step (2) is (40-70)°C, the stirring speed is (400-800) rpm, and the solvent is one of dichloromethane, ethyl acetate, and butyl acetate.

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