A solid propellant based on an imidazolium salt ionic liquid bonding agent

Abstract

The application provides a solid propellant based on an imidazolium salt ionic liquid bonding agent, which comprises a bonding agent, and the bonding agent is an imidazolium salt ionic liquid. + [X] ‑ ; wherein [R1R2IM] + is a 1,3-disubstituted imidazolium cation; [X] ‑ is an anion. The solid propellant based on the imidazolium salt ionic liquid bonding agent comprises a binder, a plasticizer, a curing agent, an ionic oxidizer, a metal fuel and the bonding agent; the imidazolium salt ionic liquid bonding agent of the application can be highly matched with the surface characteristics of high-polarity and ionic oxidizers, and has a brand-new action mechanism, so that the mechanical properties and process properties of the solid propellant containing AP, ADN, TKX-50, TYX and other oxidizers are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of solid propellant materials technology, and relates to solid propellants containing ionic oxidants, specifically to a solid propellant based on imidazolium salt ionic liquid bonding agent. Background Technology

[0002] Solid propellants, as the power source of solid rocket engines, are energetic materials with specific energy and mechanical properties, composed of a polymer binder matrix, solid oxidizer, metallic fuel, and various functional additives. Their performance directly determines the range and penetration capability of missile weapons, as well as the launch efficiency and reliability of space launch vehicles. From a microstructural perspective, solid propellants are a typical particle-reinforced composite material, and their macroscopic mechanical behavior is jointly determined by the continuous phase (binder matrix), the dispersed phase (solid filler particles), and the interfacial phase between them.

[0003] Throughout the entire service life of a propellant grain—from casting and curing, demolding and shaping, long-term storage, logistical transport to final ignition and launch—it continuously endures complex multiaxial stresses caused by thermal stress, gravity, vibration, and high-pressure overload in the combustion chamber. This necessitates that the propellant possess excellent mechanical properties, especially sufficient tensile strength and elongation, to resist crack initiation and propagation and maintain the geometric integrity of the propellant grain structure. Structural failure, resulting in internal cracks or interface debonding, will lead to a sharp increase in the combustion surface area, potentially causing an abnormal rise in combustion chamber pressure or even an explosion, resulting in catastrophic consequences.

[0004] Extensive basic research and engineering practice have repeatedly confirmed that the interfacial region between the binder matrix and solid oxidizer particles is the weakest link within solid propellants. Commonly used binders, such as hydroxyl-terminated polybutadiene (HTPB), polyethylene glycol (PEG), and glycidyl azidophosphate (GAP), have molecular chains primarily composed of nonpolar or weakly polar organic segments; while high-energy oxidizers, such as ammonium perchlorate (AP), RDX, octogen (HMX), ammonium dinitramide (ADN), and even newer generations of high-nitrogen energetic ionic salts (such as TKX-50) and bis(triazolotetraazine) bis(intrinsic) salts (TYX), exhibit strongly polar or ionic properties on their surfaces. This fundamental difference in chemical structure and physical properties means that the molecular interactions at the interface (mainly van der Waals forces and weak hydrogen bonds) are far from sufficient to resist stress concentration caused by external loads. When the local stress exceeds the interfacial bonding strength, the binder matrix peels off from the surface of the filler particles, forming micropores, a phenomenon known as "dewetting." The occurrence and spread of dehydration drastically reduces the propellant's modulus and load-bearing capacity, and provides a channel for the intrusion of combustion gases, which is the main cause of the deterioration of propellant mechanical properties and combustion instability.

[0005] To overcome this key technical challenge, since A.E. Oberth pioneered the interfacial bonding theory in the 1960s, introducing "bonding agents" into propellant formulations has become the most mainstream and effective means of enhancing the interface and inhibiting dehydration. Bonding agents, also known as coupling agents, are compounds that carry different reactive or polar functional groups at both ends or on the side groups of their molecular chains. Their ideal working model is as follows: one end is firmly anchored to the oxidant crystal surface through strong physical or chemical interactions (such as electrostatic attraction, hydrogen bonding, coordination bonds, or ionic bonds); the other end carries groups that can participate in the curing reaction (such as hydroxyl or amino groups), chemically incorporating them into the three-dimensional network structure of the adhesive during the cross-linking reaction between the adhesive prepolymer and the polyisocyanate curing agent. Thus, the bonding agent constructs a "molecular bridge" between the oxidant particles and the adhesive matrix, transforming the originally weak physical contact interface into a high-strength chemically bonded transition layer with a modulus gradient, thereby effectively transferring and dispersing stress and greatly improving interfacial adhesion and tear resistance. The amount of bonding agent used is extremely small, usually only a few thousandths of the total mass of the propellant, but it can have a decisive influence on the mechanical properties. Therefore, it is regarded as the core functional additive in the formulation of high-energy solid propellants.

[0006] After decades of unremitting research, the industry has developed bonding agents with diverse structures and mechanisms for different adhesive systems and oxidant types, which can be roughly summarized into the following categories:

[0007] First, aziridine-based bonding agents.

[0008] Representative products of this type of bonding agent are tri-(2-methylaziridinyl)phosphine oxide (MAPO) and isophthaloyl di(2-methylaziridinyl) (HX-752). Infrared spectroscopy and quantitative calculations reveal that the highly polar phospho group (P=O) in the MAPO molecule can bind with ammonium ions (NH4+) on the surface of AP crystals. + MAPO forms strong hydrogen bonds, thus achieving initial adsorption on the AP surface. More uniquely, the weakly acidic environment of AP catalyzes the ring-opening self-polymerization of the aziridine ring on MAPO, generating a tough, high-modulus polymer coating layer in situ on the AP particle surface. This coating layer not only enhances interfacial adhesion but also improves the thermal stability of AP through steric hindrance. Experiments have confirmed that MAPO can significantly improve the mechanical properties of HTPB / AP propellants. However, the bonding of MAPO is highly selective: its interaction mechanism with AP depends on the acidity of AP and the presence of ammonium ions. For nitramine oxidants (RDX, HMX) with neutral surface groups such as nitro groups, MAPO cannot form effective adsorption, resulting in minimal enhancement.

[0009] Second, alcoholic amines and polyamines as bonding agents.

[0010] These compounds include triethanolamine (TEA), boron trifluoride triethanolamine complex (T313), and various polyethylenepolyamines. Their bonding mechanism primarily utilizes the tertiary or primary / secondary amine groups in the molecule as Lewis bases, which react with weakly acidic ammonium ions on the AP surface through an acid-base neutralization reaction, forming ionic bonds and achieving tight adsorption. T313 is a standout among these compounds; it not only enhances interfacial adhesion, but its boron content is also believed to participate in the regulation of the matrix network. However, the application of such bonding agents has significant limitations: First, the high reactivity of the amine groups with isocyanate curing agents leads to a rapid increase in the viscosity of the propellant slurry during casting, resulting in poor flowability and a significantly shortened pot life. Second, amines are alkaline and have poor compatibility with nitrate ester plasticizers (such as nitroglycerin NG and glycerol trinitrate BTTN), accelerating the decomposition of nitrate esters and posing serious safety hazards. Therefore, they cannot be used in higher-energy NEPE propellants.

[0011] Third, borate ester bonding agents.

[0012] Boron ester bonding agents (BEBA) are an important class of bonding agents developed for nitramine oxidant (RDX, HMX) systems. Their core mechanism of action lies in utilizing the electron-deficient property of the boron atom (B), i.e., sp... 2 The empty p orbitals present in the hybrid orbitals act as Lewis acids, accepting the lone pair electrons from the nitrogen (N) or oxygen (O) atoms on the nitro group (-NO2) in the nitramine molecule, forming N→B or O→B coordination bonds of a certain strength. Simultaneously, by introducing flexible segments containing hydroxyl groups into the molecule, it can participate in the curing reaction.

[0013] To overcome the shortcomings of early linear borate esters, which are prone to hydrolysis and failure, researchers have continuously improved their performance through structural modification. For example, Yu Haijiang, Mao Jiagan, and others designed and synthesized borate esters containing five- or six-membered cyclic structures, significantly improving their hydrolytic stability by utilizing the steric hindrance effect of the cyclic structure. Huang Wenqian et al. systematically studied the application of cyclic borate esters (CBE) with different alkyl chain lengths in the HTPB / RDX system using a combination of molecular dynamics simulations and experiments. They found that CBEs can form strong van der Waals interactions and hydrogen bonds on the RDX surface, significantly improving interfacial tensile strength and separation work, with the effect increasing with increasing chain length. Hu Qunzhi et al. introduced flexible polyester segments and strongly polar groups such as cyano (-CN) and amino groups into the borate ester molecule to synthesize the multifunctional bonding agent DBA. While improving interfacial adhesion, DBAs also significantly reduced the viscosity of the propellant slurry through "internal lubrication," increasing the room temperature and high temperature tensile strength of the propellant by 33.4% and 21.1%, respectively. Although borate ester bonding agents have achieved remarkable results in nitramine systems, the strength of their coordination bonds is still weaker than that of ionic bonds. When faced with ionic oxidants such as ADN or TKX-50, which have stronger surface ionic fields and higher polarity, their adsorption competitiveness and stability face severe challenges.

[0014] Fourth, neutral polymer bonding agent (NPBA).

[0015] In the 1990s, to address the challenges posed by the large amount of nitrate plasticizers in NEPE propellants, American scholars Kim CS et al. creatively proposed the concept of neutral polymer bonding agents (NPBA). In NEPE propellants, polar nitrate plasticizers tend to migrate and dissolve on the surface of polar nitramine fillers (such as HMX), forming a "soft interface layer" with extremely poor mechanical properties. Meanwhile, traditional small-molecule polar bonding agents also dissolve in the plasticizer due to the "like dissolves like" principle, failing to exert their bonding effect. NPBA is a high-molecular-weight polymer randomly copolymerized from monomers such as acrylonitrile (AN), methyl acrylate (MA), and hydroxyethyl acrylate (HEA). Its ingenious design lies in precisely controlling the proportion of comonomers so that their solubility parameters are compatible with the system during high-temperature mixing, allowing them to dissolve. During cooling and curing, phase separation occurs, coating the surface of the nitramine filler in a "precipitation-deposition" manner, thus avoiding interference from plasticizers.

[0016] Zhang Pingan, Feng Zhuokeng, and others, combining experiments and molecular dynamics simulations, have revealed the mechanism of action of NPBA: the cyano groups (-CN) on the NPBA molecular chain can generate strong van der Waals forces with the nitro groups on the HMX surface, while the hydroxyl groups (-OH) form hydrogen bonds. The synergistic effect of these two groups ensures strong adsorption. The hydroxyl groups then participate in the cross-linking reaction, "anchoring" the HMX particles to the adhesive network, forming a high-modulus tear-resistant layer. Despite the great success of NPBA, it also has certain limitations. As a random copolymer, the sequence structure and functional group distribution of its molecular chain are difficult to control precisely, which hinders in-depth analysis of structure-activity relationships and refined performance regulation. More importantly, the interaction between NPBA and oxidant surfaces is still mainly based on van der Waals forces and dipole interactions. For ionic oxidants (AP, ADN, TYX, etc.), its adsorption strength may be insufficient due to the strong ionic fields present on their surfaces.

[0017] Fifth, hyperbranched polymer bonding agents.

[0018] To overcome the limitations of linear polymers in terms of functional group density and structural precision, hyperbranched polymers have been introduced into the design of bonding agents. Hu Weiyu et al. synthesized terminally hydroxyl hyperbranched polyethers (HPMs) via cationic ring-opening polymerization and prepared a series of hyperbranched polyether bonding agents (GHPBs) by introducing different proportions of cyano and ester groups at their ends through transesterification. Benefiting from the three-dimensional spherical structure and abundant terminal functional groups of hyperbranched polymers, GHPBs exhibit excellent adsorption performance on RDX surfaces, and their interfacial adhesion work increases with increasing generation and cyano content. However, the synthesis of such bonding agents is complex and costly, and they are currently still in the laboratory research stage.

[0019] In summary, while the existing bonding agent technology system is relatively rich, its inherent limitations become increasingly apparent when facing the increasing number of highly polar and ionic oxidizers (such as AP, ADN, TKX-50, TYX, etc.) in next-generation solid propellants. These limitations are mainly reflected in the following aspects: First, the mechanism of action is mismatched.

[0020] The adsorption of existing bonding agents on oxidant surfaces mainly relies on secondary bonding interactions such as hydrogen bonds, van der Waals forces, and coordination bonds. The strength of these forces differs in energy level from the strong electrostatic field formed by positive and negative ions on the surface of ionic oxidants. This makes it difficult for bonding agent molecules to form a stable and dense adsorption layer on the surface, making them easily displaced by other polar components in the system (such as plasticizers), resulting in insufficient interfacial adhesion strength.

[0021] Second, interfacial wetting and stress transfer barriers.

[0022] Ionic oxidants exhibit high hydrophilicity, while commonly used binder matrices (such as HTPB) are hydrophobic. Traditional bonding agents have limited ability to reduce interfacial tension when reconciling such drastically different hydrophilic / hydrophobic interfaces, leading to insufficient spread of the binder on the filler surface and micro-defects at the interface. Furthermore, the interfacial layer formed by traditional bonding agents struggles to establish a continuous modulus gradient between rigid inorganic crystals and flexible organic matrices, resulting in low stress transfer efficiency and a tendency for stress concentration at abrupt interfacial changes.

[0023] Third, the side effects of process performance.

[0024] Some bonding agents that interact with AP (such as alcohol amines) are too reactive, which can sacrifice the process flowability and pot life of the slurry and affect the casting quality of large and complex shaped slurries.

[0025] Fourth, sensitivity to plasticizer environment.

[0026] In NEPE propellants containing a large amount of polar plasticizers, the adsorption stability of existing bonding agents in the plasticizer environment is significantly reduced, and the interfacial softening phenomenon is difficult to eliminate. Summary of the Invention

[0027] To address the shortcomings of existing technologies, the present invention aims to provide a solid propellant based on an imidazolium salt ionic liquid bonding agent, thereby solving the technical problem that the matching degree between the traditional bonding agent and the surface characteristics of the highly polar ionic oxidant in existing solid propellants needs to be further improved.

[0028] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0029] A solid propellant based on an imidazolium salt ionic liquid bonding agent includes a bonding agent, wherein the bonding agent is an imidazolium salt ionic liquid.

[0030] Specifically, the structural formula of the imidazolium salt ionic liquid is [R1R2IM]. + [X] - ; In the formula: [R1R2IM] + It is a 1,3-disubstituted imidazole cation; [X] - It is an anion; R1 and R2 are each independently selected from straight-chain or branched alkyl groups from C1 to C6; The anion is selected from thiocyanate (SCN). - ), dicyandiamide ([N(CN)2]) - ), tricyanomethane ([C(CN)3) -), Tetracyanoborate ([B(CN)4)) - ) or tetrafluoroborate (BF) - ).

[0031] The present invention also has the following technical features.

[0032] Preferably, R1 is methyl, R2 is n-butyl, and [R1R2IM] + The cation is 1-butyl-3-methylimidazolium; the anion is thiocyanate (SCN). - ).

[0033] Preferably, the imidazolium salt ionic liquid has a mass percentage content of 0.05% to 0.50% in the solid propellant.

[0034] More preferably, the imidazolium salt ionic liquid has a mass percentage content of 0.10% to 0.30% in the solid propellant.

[0035] Most preferably, the imidazolium salt ionic liquid has a mass percentage content of 0.15% to 0.20% in the solid propellant.

[0036] Specifically, the solid propellant based on imidazolium salt ionic liquid bonding agent includes a binder, plasticizer, curing agent, ionic oxidant, metallic fuel, and bonding agent.

[0037] Preferably, the adhesive is hydroxyl-terminated polybutadiene (HTPB) or polyglycidyl azidophosphate (GAP).

[0038] Preferably, the plasticizer is dioctyl sebacate (DOS) or bis(2,2-dinitropropyl)formaldehyde (BDNPF / A).

[0039] Preferably, the curing agent is toluene diisocyanate (TDI) or a polyfunctional isocyanate.

[0040] Preferably, the ionic oxidant is ammonium perchlorate (AP) or ammonium dinitramide (ADN).

[0041] Preferably, the metal fuel is spherical aluminum powder (Al).

[0042] Furthermore, by weight, the raw materials consist of the following components: 10.00 to 12.00 parts of adhesive, 2.00 to 3.00 parts of plasticizer, 0.80 to 1.35 parts of curing agent, 65.50 to 68.00 parts of oxidant, 18.00 to 19.00 parts of aluminum powder, and 0.15 to 0.20 parts of bonding agent, with the total weight of the raw materials being 100 parts.

[0043] Compared with the prior art, the present invention has the following technical effects.

[0044] (I) The imidazolium salt ionic liquid bonding agent of the present invention can be highly matched with the surface characteristics of highly polar and ionic oxidants, and has a novel mechanism of action to significantly improve the mechanical and processing properties of solid propellants containing oxidants such as AP, ADN, TKX-50, and TYX.

[0045] (II) Innovative Mechanism of the Invention: This invention proposes and verifies the concept of "ionic bonding agent," pioneering the application of the self-assembly principle of the interfacial electric double layer of ionic liquids to the interfacial strengthening of solid propellants. This bonding mechanism based on strong electrostatic interactions between "ions" fundamentally solves the problem of mismatch between the surface interaction mechanisms of traditional neutral macromolecular bonding agents and highly polar ionic oxidants.

[0046] (III) The highly efficient enhancement effect of the present invention: Experimental data show that only 0.1% to 0.3% of [R1R2IM] by the total mass of the propellant needs to be added. + [X] - This invention can increase the tensile strength of AP-containing HTPB propellants by 50% to 150% and the elongation at break by 20% to 60%, far exceeding the effect of traditional bonding agents with the same amount added. For propellant systems containing novel oxidizers such as ADN, TKX-50, and TYX, the enhancing effect of this invention is even more pronounced.

[0047] (IV) Optimization of process performance of the present invention: The bonding agent of the present invention has the dual functions of interface enhancer and high-efficiency internal lubricant, which can significantly reduce the viscosity of propellant slurry, improve its fluidity and castability, and provide a strong guarantee for the high-quality manufacturing of propellant grains with high solid content, large size and complex configuration.

[0048] (V) Universality and Synergy of the Invention: This ionic liquid bonding agent is not only effective for single AP or ADN systems, but also exhibits good adaptability to mixed oxidant systems such as AP / ADN / TKX-50 / TYX. Furthermore, it can be used in combination with a small amount of traditional bonding agents to produce a synergistic enhancement effect, providing ample room for flexible formulation design.

[0049] (VI) The high stability and security of the present invention: [R1R2IM] + [X] - It has extremely high thermal stability and chemical inertness, extremely low vapor pressure, is not easily volatilized or migrated, and has good compatibility with all components of the propellant (including nitrate ester plasticizer), which can ensure the structural integrity and performance stability of the propellant during long-term storage.

[0050] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0051] It should be noted that all materials and equipment used in this invention, unless otherwise specified, are those known in the art. Unless otherwise specified, "parts" and "%" in the following text refer to percentages by mass.

[0052] The overall technical concept of this invention is as follows: If an ionic liquid with a specific structure is introduced into a solid propellant system, its cations and anions are highly likely to undergo a similar spontaneous assembly process under the induction of a strong ionic field on the surface of an ionic oxidant (such as AP, ADN). The anions are tightly anchored to the surface cation sites, forming a high-modulus inner layer; the imidazole ring of the cation pairs with the anion, and its alkyl side chain faces the external binder matrix, forming a flexible outer layer with good compatibility with the matrix. This biomimetic "electric double layer" interface structure will fundamentally change the interface bonding mode from traditional neutral molecule adsorption to strong electrostatic anchoring and self-assembly between ions, and is expected to overcome a series of problems such as the mismatch of the action mechanism of existing bonding agents in ionic oxidant systems, poor interface wetting, and low stress transfer efficiency.

[0053] Based on the above technical concept, this invention proposes for the first time the use of imidazolium salt ionic liquids with specific structures, particularly [R1R2IM]. + [X] - This is a technical solution for applying a highly efficient "ionic bonding agent" in the field of solid propellants.

[0054] The core innovation of this invention lies in its innovative application, for the first time, of the unique interfacial self-assembly behavior of ionic liquids to the interfacial strengthening of solid propellants. Its mechanism of action is fundamentally different from any existing bonding agent. The core innovation of this invention is detailed below. First, strong electrostatic anchoring and interface reconstruction: when the [R1R2IM] of the present invention... + [X] - After the bonding agent is introduced into the propellant system, its molecules come into contact with the surface of the ionic oxidant (such as AP) during mixing and curing. The periodically arranged positive ions (NH4+) on the AP crystal surface... + ) and negative ions (ClO4) - A strong electrostatic field is formed. Under the induction of this strong electrostatic field, [R1R2IM]... + [X] - The cations and anions will undergo directional migration and rearrangement. SCN, with its smaller size and highly localized charge, - Anions will preferentially react with NH4 on the AP surface. + A strong Coulombic attraction occurs, forming a tight anionic inner layer characterized by chemisorption. Subsequently, [BMIM] + Cations react with SCN under electrostatic forces- Anions pair to form a second layer. Due to the delocalized π electrons of the imidazole ring, it tends to adsorb in a planar manner on the plane composed of anions, while its flexible butyl side chains extend outward toward the binder matrix. This process is similar to the formation of a Helmholtz double layer on the electrode surface, but its essence is the in-situ construction of a nanoscale interfacial transition layer composed of ordered cations and anions on the oxidant surface.

[0055] Second, a modulus gradient interface layer is constructed: the aforementioned ordered ion assembly layer itself possesses unique mechanical properties. The dense ion pairs in the inner layer endow this region with high modulus and rigidity, effectively transferring stress from the high-modulus oxidant crystal outwards. Meanwhile, the flexible butyl chains in the outer layer interpenetrate and entangle with the adhesive matrix molecular chains, forming a gradient region with gradually decreasing modulus that matches the bulk modulus of the adhesive matrix. This continuous modulus transition structure from an inorganic rigid crystal to an organic flexible matrix is ​​key to the efficient stress transfer and avoidance of interfacial stress concentration in the bonding agent of this invention, similar to the effect of setting a stress-relieving layer in macroscopic engineering.

[0056] Third, enhance interfacial compatibility and adhesion: [BMIM] + The cation is a typical amphiphilic ion. Its imidazole ring head has a certain polarity, exhibiting good affinity with polar adhesive segments such as polyether (PEG) and polyester (PCL); while its butyl side chain is nonpolar, exhibiting good compatibility with nonpolar adhesive backbones such as HTPB. This unique amphiphilic property makes the bonding agent of this invention an ideal "interfacial compatibilizer." It can significantly reduce the interfacial tension between the oxidant and the adhesive matrix, greatly improve the wetting and spreading behavior of the adhesive on the surface of oxidant particles, thereby significantly enhancing interfacial adhesion work and reducing the formation of initial defects such as interfacial micropores.

[0057] Fourth, viscosity reduction and process optimization of the slurry: room temperature ionic liquid [R1R2IM] + [X] - It possesses a viscosity significantly lower than that of traditional polymeric bonding agents. When it adsorbs onto the surface of oxidant particles through the aforementioned mechanism, its flexible alkyl chain layer acts as a "molecular lubricating film" on the particle surface, effectively reducing friction between oxidant particles and between particles and the container wall in high-solids-content systems. Therefore, the bonding agent of this invention can significantly reduce the initial viscosity and yield stress of propellant slurry, improve its leveling and castability, and is particularly suitable for manufacturing high-fill-fraction propellant columns with complex geometries.

[0058] In this invention, the structural formula of the imidazolium salt ionic liquid can also be represented as follows: ; In the formula: [R1R2IM] + It is a 1,3-disubstituted imidazole cation; [X] - It is an anion.

[0059] The preferred embodiment of this invention is the imidazolium salt ionic liquid [R1R2IM]. + [X] - In this context, R1 is methyl, R2 is n-butyl, and [R1R2IM] is a methyl group. + It is a 1-butyl-3-methylimidazolium cation; the anion is thiocyanate (SCN). - The imidazolium salt ionic liquid is an imidazolium salt ionic liquid known in the art; the preparation method of the imidazolium salt ionic liquid also adopts the preparation method of imidazolium salt ionic liquid known in the art.

[0060] The role of the preferred imidazolium salt ionic liquid in this invention is completely different from its role in the prior art, specifically in the following aspects.

[0061] First, the dimensional isolation of application domains is completely different from that of technical issues.

[0062] The existing technology pertains to electrochemical energy storage, and the technical problem it aims to solve is how to understand and optimize the electric double layer (EDL) structure of ionic liquid electrolytes on the surface of electrode materials to improve the capacitance performance of supercapacitors. The research focuses on graphene electrodes immersed in a large volume of ionic liquid, with key performance indicators including specific capacitance, energy density, and power density.

[0063] This invention belongs to the field of solid propellant materials technology. The technical challenge it addresses is how to enhance the bonding strength at the interface between two phases and suppress the "dewetting" phenomenon under stress in a solid multiphase system composed of a polymer binder and a highly polar ionic oxidant (AP, ADN, etc.), thereby improving the tensile strength, elongation at break, and other mechanical properties of the propellant. Simultaneously, it is also necessary to reduce the processing viscosity of high-solids-content propellant slurries.

[0064] Second, the fundamental difference between the driving force and the essential attributes of the interface.

[0065] This is the most core and essential difference between the two.

[0066] In the existing technology, [R1R2IM] + [X] -The sole and direct driving force for the formation of an ordered electric double layer structure by ionic liquids on the graphene electrode surface is the externally applied electric field. When the external electric field is removed or the voltage polarity is changed, the electric double layer structure will dissociate, reconstruct, or even dissipate. Essentially, it is a physical, dynamically reversible ion arrangement phenomenon driven by external energy.

[0067] In contrast, the interface formation of this invention is entirely completed in a chemical curing environment without any external electric field. The driving force originates from the strong Coulombic interaction spontaneously generated by the chemical potential between the target compound—3,3'-([4,4'-bipyridine]-1,1'-diyl-1,1'-dimethylene)bis(propane-1-sulfonate)—and the static, periodic, strong ionic field built into the crystal surface of the ionic oxidant (such as AP). As a result, this zwitterionic compound, through its sulfonate anion (-SO32-), allows the interface to be formed... - ) group, and ammonium ions (NH4) on the AP surface + This forms a stable, irreversible ionic chemisorption. This is a thermodynamically stable chemical interface, not a physical double layer dependent on external energy. To classify a dynamic physical structure maintained by external electrical energy as the same as a static chemical interface spontaneously formed by internal chemical energy represents a fundamental confusion in scientific principles.

[0068] Third, the resulting interfaces have vastly different structures and functions.

[0069] Based on the aforementioned differences in driving forces and essence, the two interfaces exhibit distinctly different characteristics in terms of structure, composition, and function.

[0070] The interfaces formed in existing technologies are classic bilayer structures composed of alternating layers of anions and cations. The function of this structure is purely electrical: to store charge and facilitate rapid charging and discharging. Ideally, the interface should allow ions to migrate and deflect rapidly under the influence of an electric field; that is, from a mechanical perspective, the interface should be soft and unstable.

[0071] The interface formed in this invention is an integrated gradient interface consisting of a chemisorbed sulfonate inner layer and an oriented bipyridine organic framework outer layer. Its function is mechanical: to transfer and disperse stress. The inner layer exhibits high modulus due to strong ionic bonds, while the outer layer exhibits flexibility due to the entanglement of alkyl chains with the binder matrix, thus constructing a mechanical buffer layer with a continuous modulus transition between the rigid oxidant and the flexible matrix. This structure is designed to resist interfacial separation, which is completely opposite in design goals and structural characteristics to existing interfacial structures that pursue rapid ion migration.

[0072] Fourth, unexpected technological effects.

[0073] It is important to emphasize that the technical solution of this invention not only solves the problem of interfacial mechanical enhancement, which has never been addressed in existing technologies, but also achieves the unexpected dual effects of "mechanical enhancement" and "process viscosity reduction." Existing technologies teach the electrochemical behavior of ionic liquids as the main electrolyte, while this invention utilizes the unique function of zwitterionic compounds as interfacial modifiers and molecular lubricants when added in trace amounts (0.1wt% to 0.3wt%). This "small amount, high efficiency" and "killing two birds with one stone" characteristic is the unexpected technical effect brought about by this invention.

[0074] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of the present invention fall within the protection scope of the present invention.

[0075] Example 1: This embodiment provides a solid propellant based on an imidazolium salt ionic liquid bonding agent, which comprises the following raw materials in parts by mass.

[0076] Hydroxyl-terminated polybutadiene (HTPB) adhesive (R-45M, number average molecular weight 2800): 10.00 parts.

[0077] Dioctyl sebacate (DOS) plasticizer: 2.00 parts.

[0078] Toluene diisocyanate (TDI) curing agent (purity >99%): 0.80 parts.

[0079] Ammonium perchlorate (AP) ionic oxidant (using III gradation, average particle size range of 5 μm to 200 μm): 68.00 parts.

[0080] Spherical aluminum powder (Al, average particle size 29μm): 19.00 parts.

[0081] Bonding agent: 0.20 parts.

[0082] In this embodiment, the bonding agent used is an imidazolium salt ionic liquid [R1R2IM]. + [X] - Where R1 is methyl, R2 is n-butyl, [R1R2IM] + It is a 1-butyl-3-methylimidazolium cation; the anion is thiocyanate (SCN). - (The purity of this imidazolium salt ionic liquid is >99%, and it was purchased from Anage Reagent or Inokai Reagent).

[0083] The preparation method of the solid propellant based on imidazolium salt ionic liquid bonding agent in this embodiment includes the following steps: A 5L standard vertical mixer is used. First, HTPB, DOS, and [R1R2IM] are mixed... +[X] - The bonding agent is added to a mixing pot and premixed at 60°C for 15 minutes until homogeneous. Then, aluminum powder and each grade of AP are added sequentially, and mixed under vacuum (≤10 mmHg) for 60 minutes. Finally, TDI is added, and vacuum mixing continues for 30 minutes. The resulting slurry is poured into a standard PTFE mold coated with a release agent and cured in a 70°C oven for 7 days to obtain the propellant billet.

[0084] Performance Testing: Referring to GJB770B-2005 "Test Methods for Gunpowder", the cured propellant billet was cut into standard dumbbell-shaped specimens and subjected to uniaxial tensile testing on an INSTRON 5567 electronic universal testing machine. The test temperature was 20℃, and the tensile rate was 100 mm / min. The tensile strength was recorded. s m ) and elongation at break ( e b (See Table 1 for detailed data.) The viscosity of the slurry after mixing was tested using a HAAKEMARS 60 rotational rheometer.

[0085] Example 2: This embodiment provides a solid propellant based on an imidazolium salt ionic liquid bonding agent, which comprises the following raw materials in parts by mass.

[0086] Glycidyl azide (GAP) adhesive (number average molecular weight 3000): 12.00 parts.

[0087] Bis(2,2-dinitropropyl)formaldehyde (BDNPF / A) plasticizer: 3.00 parts.

[0088] Multifunctional isocyanate curing agent (N100): 1.35 parts.

[0089] Spherical dinitramide ammonium (ADN) ionic oxidant (average particle size approximately 100 μm): 65.50 parts.

[0090] Spherical aluminum powder (Al): 18.00 parts.

[0091] Bonding agent: 0.15 parts.

[0092] In this embodiment, the bonding agent is the same as that in Example 1.

[0093] The preparation method in this embodiment is basically the same as that in Example 1, except that in this embodiment, the curing temperature is 50°C and the curing time is 7 days.

[0094] The performance testing method in this embodiment is the same as that in Embodiment 1, and the mechanical performance data is recorded in Table 1.

[0095] Comparative Example 1: (Blank Control) This comparative example provides a solid propellant, which differs from Example 1 in that it does not contain the imidazolium salt ionic liquid [R1R2IM]. + [X] - The bonding agent is replaced with an equal amount (0.2 parts) of ammonium perchlorate (AP) ionic oxidant.

[0096] The preparation method of this comparative example is basically the same as that in Example 1.

[0097] The performance testing method for this comparative example is the same as that for Example 1, and the mechanical performance data are recorded in Table 1.

[0098] Comparative Example 2: (Traditional bonding agent control) This comparative example provides a solid propellant, which differs from Example 1 in that an equal amount (0.20 parts) of a conventional bonding agent, namely tri-(2-methylaziridinyl)phosphine oxide (MAPO), is used instead of the imidazolium salt ionic liquid [R1R2IM] given in Example 1. + [X] - Bonding agent.

[0099] In this comparative example, the tri-(2-methylaziridinyl)phosphine oxide (MAPO) bonding agent used is a tri-(2-methylaziridinyl)phosphine oxide (MAPO) bonding agent known in the art.

[0100] The preparation method of this comparative example is basically the same as that in Example 1.

[0101] The performance testing method for this comparative example is the same as that for Example 1, and the mechanical performance data are recorded in Table 1.

[0102] Comparative Example 3: (Blank Control) This comparative example provides a solid propellant, which differs from Example 2 in that it does not contain the imidazolium salt ionic liquid [R1R2IM]. + [X] - The bonding agent is replaced with an equal amount (0.15 parts) of spheroidized dinitramide ammonium (ADN) ionic oxidant.

[0103] The preparation method of this comparative example is basically the same as that in Example 2.

[0104] The performance testing method for this comparative example is the same as that for Example 2, and the mechanical performance data are recorded in Table 1.

[0105] Comparative Example 4: (Traditional bonding agent control) This comparative example provides a solid propellant, which differs from Example 2 in that an equal amount (0.15 parts) of a conventional bonding agent, namely a neutral polymeric bonding agent (NPBA), is used instead of the imidazolium salt ionic liquid [R1R2IM] given in Example 1. + [X] - Bonding agent.

[0106] In this comparative example, the neutral polymer bonding agent (NPBA) used is a neutral polymer bonding agent (NPBA) known in the art; the number average molecular weight of the neutral polymer bonding agent (NPBA) is ( M n The value is 25000. In the neutral polymer bonding agent (NPBA), the molar ratio of the three comonomers acrylonitrile (AN), methyl acrylate (MA), and hydroxyethyl acrylate (HEA) is 1:0.3:0.2.

[0107] The preparation method of this comparative example is basically the same as that in Example 1.

[0108] The performance testing method for this comparative example is the same as that for Example 1, and the mechanical performance data are recorded in Table 1.

[0109] Table 1 Comparison of mechanical properties and slurry viscosity between the examples and comparative examples

[0110] Results analysis.

[0111] As shown in Table 1, the mechanical properties are significantly improved: compared to Comparative Example 1, the tensile strength of Example 1 jumps from 0.68 MPa to 1.48 MPa, an increase of 117%; the elongation at break also increases from 22.5% to 46.2%, an increase of over 105%. For Example 2 of the ADN system, compared to Comparative Example 3, its strength and elongation also show astonishing improvements of over 116% and 134%, respectively. This eloquently demonstrates the unparalleled reinforcing efficacy of the ionic bonding agent of the present invention in systems such as AP and ADN.

[0112] As shown in Table 1, the comparative advantage is significant: compared with Comparative Example 2 (MAPO) and Comparative Example 4 (NPBA) which use the best existing bonding agents, the mechanical properties of the embodiments of the present invention have an overwhelming advantage, further verifying that the "ion-ion" bonding mechanism of the present invention has a more fundamental compatibility with ionic oxidants.

[0113] As shown in Table 1, the simultaneous optimization of process performance: the viscosity of the slurry in the examples is significantly lower than that in their respective comparative examples. This intuitively demonstrates the unique advantage of the bonding agent of the present invention as a "molecular lubricant", which has significant engineering implications for the manufacture of high solids content propellants.

[0114] Under the influence of a strong ionic field in an AP crystal, [R1R2IM] + [X] - The cations and anions spontaneously assemble into an ordered electric double layer structure. SCN - The anion is tightly anchored to the NH4+ of AP. + On the surface, a high-modulus inner layer is formed; while [BMIM] + The cations are oriented, with their alkyl chains extending outward and entangled with the HTPB molecular chains, thus constructing a gradient interface layer with a continuous modulus transition from a rigid oxidant to a flexible adhesive. This innovative interface structure is the fundamental reason for the superior performance of the bonding agent of this invention.

[0115] In summary, the present invention provides [R1R2IM] + [X] - Imidazolium salt ionic liquid bonding agents, represented by [example agent name], have revolutionized traditional bonding agents by solving the problems of mechanism mismatch and limited enhancement effects in ionic oxidant systems through unique ionic electrostatic anchoring and interfacial self-assembly mechanisms. They also possess excellent process optimization capabilities. Their superior versatility, high efficiency, and stability indicate broad application prospects and immeasurable technological value in the research and development and production of next-generation high-energy, high-structural-integrity solid propellants.

Claims

1. A solid propellant based on an imidazolium salt ionic liquid bonding agent, comprising the bonding agent, characterized in that, The bonding agent is an imidazolium salt ionic liquid.

2. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 1, characterized in that, The structural formula of the imidazolium salt ionic liquid is [R1R2IM]. + [X] - ; In the formula: [R1R2IM] + It is a 1,3-disubstituted imidazole cation; [X] - It is an anion; R1 and R2 are each independently selected from straight-chain or branched alkyl groups from C1 to C6; The anion is selected from thiocyanate, dicyandiamide, tricyanomethane, tetracyanoborate, or tetrafluoroborate.

3. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 2, characterized in that, R1 is methyl, R2 is n-butyl, [R1R2IM] + The cation is 1-butyl-3-methylimidazolium; the anion is thiocyanate (SCN). - ).

4. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 1, characterized in that, The imidazolium salt ionic liquid has a mass percentage content of 0.05% to 0.50% in the solid propellant.

5. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 4, characterized in that, The imidazolium salt ionic liquid has a mass percentage content of 0.10% to 0.30% in the solid propellant.

6. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 5, characterized in that, The imidazolium salt ionic liquid has a mass percentage content of 0.15% to 0.20% in the solid propellant.

7. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 1, characterized in that, The solid propellant based on imidazolium salt ionic liquid bonding agent includes a binder, plasticizer, curing agent, ionic oxidant, metallic fuel, and bonding agent.

8. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 7, characterized in that, The adhesive is hydroxyl-terminated polybutadiene or polyazoyl glycidyl ether; The plasticizer is dioctyl sebacate or bis(2,2-dinitropropyl)formaldehyde; The curing agent is toluene diisocyanate or a polyfunctional isocyanate; The ionic oxidant is ammonium perchlorate or ammonium dinitramide; The metal fuel is spherical aluminum powder.

9. The solid propellant based on imidazolium salt ionic liquid bonding agent as described in claim 7, characterized in that, The product comprises the following raw materials by weight: 10.00 to 12.00 parts of adhesive, 2.00 to 3.00 parts of plasticizer, 0.80 to 1.35 parts of curing agent, 65.50 to 68.00 parts of oxidant, 18.00 to 19.00 parts of aluminum powder, and 0.15 to 0.20 parts of bonding agent, with a total weight of 100 parts.

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