A silicone block copolymer, a method for preparing the same, and use thereof in solid propellants

Abstract

The application discloses a kind of organic silicon block copolymer and its preparation method and application in solid propellant.The block copolymer is obtained by coupling carbon chain polymer copolymerized by butyl acrylate and acrylonitrile with silicon oil synthesized by isocyanate base double end cap and cyclosiloxane.The block copolymer can be physically adsorbed on the surface of oxidant particle in solid propellant by cyano and urethane group generated in coupling process, and crosslinked into solid propellant binder network structure by hydroxyl in bonding agent molecular structure, which can easily infiltrate the surface of oxidant particle in solid propellant, thereby providing very excellent bonding effect.In addition, the bonded solid propellant grain of the application is not easy to be damaged and "dewetted" even in high temperature condition, which is very effective for improving the high temperature mechanical properties of composite solid propellant.The bonding agent has the advantages of easy to obtain raw materials, easy to realize preparation process, and is conducive to popularization and application.

Description

Technical Field

[0001] This invention relates to an organosilicon block copolymer, its preparation method, and its application as a solid propellant bonding agent, belonging to the technical fields of polymer synthesis, fine chemicals, and solid propellant applications. Background Technology

[0002] Composite solid propellants are energetic composite polymer materials with polymers as the continuous phase and solid particles as fillers. Their mechanical properties are influenced by many factors, and ensuring effective adhesion between the solid particles and the binder interface is a necessary condition for composite solid propellants to achieve excellent mechanical properties. To improve the bonding strength between the oxidizer and binder interface in solid propellants, bonding agents are often added to the propellant formulation. According to the bonding principle of solid propellants, the bonding agent molecule design must meet three conditions: it must be able to aggregate on the surface of the oxidizer solid particles filling the propellant; it must be able to form a hard and tough outer shell layer on the surface of the oxidizer particles; and it must have sufficient remaining functional groups to form the main chemical bonds, enabling the binder network to chemically bond with the aforementioned hard shell layer.

[0003] Currently, most small-molecule bonding agents used in solid propellants are small-molecule polar compounds effective against ammonium perchlorate (AP), such as aziridines and alkanolamine derivatives. Among them, aziridines (such as tri-(2-methylaziridine)phosphine oxide, code name MAPO) are the most widely used. In addition, a polymeric macromolecular bonding agent (NPBA) was first disclosed in 1990. NPBA is a neutral polymeric bonding agent that is a copolymer of acrylonitrile and hydroxyl acrylate, with nitrile groups (C≡N) and hydroxyl groups (OH) introduced into the macromolecular structure. The inventors previously disclosed a macromolecular bonding agent composed of acrylate copolymers containing dicyano groups. Due to the presence of two nitrile groups on the functional units of the copolymer, it has strong adsorption and achieves excellent bonding effect. However, the surface migration characteristics of this bonding agent still need improvement. How to promote the surface migration of the bonding agent while ensuring compatibility, thereby achieving efficient bonding, has been a long-term goal pursued by energetic materials experts. Summary of the Invention

[0004] This invention utilizes the coupling of organosilicon segments and polar polymer segments to obtain a block copolymer type bonding agent with high migration characteristics that can improve the high-temperature mechanical properties of solid propellants.

[0005] The technical solution adopted in this invention is: An organosilicon block copolymer has the following chemical structural formula: ; Where X is 4-cyanopentyl; p = 2–50; q = 2–50; m = 4–100; n = 1–10.

[0006] This invention discloses a method for preparing the above-mentioned organosilicon block copolymer, comprising the following steps: reacting a cyano polymer and an isocyanate-based silicone oil to obtain the organosilicon block copolymer.

[0007] In this invention, the reaction of the cyanopolymer and isocyanate-based silicone oil is carried out under the catalysis of an organotin compound, such as dibutyltin dilaurate; the reaction temperature is 50–120°C, and the reaction time is 1–8 hours. Preferably, the mass ratio of the cyanopolymer, isocyanate-based silicone oil, and organotin compound is (100–500):(5–30):(0.005–0.05). More preferably, the mass ratio of the cyanopolymer, isocyanate-based silicone oil, and organotin compound is (150–300):(8–20):(0.01–0.03).

[0008] In this invention, isocyanate-based silicone oil is prepared using cyclosiloxane monomers and isocyanate double-ended caps as raw materials; cyanopolymer is prepared by polymerization using 4,4-azobis(4-cyanopentanol) as an initiator and butyl acrylate and acrylonitrile as raw materials. Preferably, methanesulfonic acid compound is used as a catalyst in the preparation of isocyanate-based silicone oil; the polymerization temperature is below 90°C, and the time is 1–24 hours. Preferably, the polymer reaction is carried out under nitrogen atmosphere, and the polymerization temperature is 85–90°C.

[0009] This invention discloses a composite solid propellant comprising an oxidant and a binder, and further comprising the aforementioned organosilicon block copolymer as a bonding agent.

[0010] This invention discloses the application of the above-mentioned organosilicon block copolymer in solid propellants.

[0011] Specifically, the organosilicon block copolymer is used as a bonding agent in solid propellants. Preferably, the organosilicon block copolymer improves the mechanical properties of the solid propellant.

[0012] The present invention discloses a method for preparing an organosilicon block copolymer, comprising isocyanate dual-end synthesis, ring-opening polymerization to prepare isocyanate-based silicone oil, free radical polymerization to prepare cyano polymer, and coupling copolymerization reaction to obtain the organosilicon block copolymer. Specifically, isocyanate dual-ends are prepared using amino dual-ends and solid phosgene as raw materials; isocyanate silicone oil is prepared using cyclosiloxane monomers and isocyanate dual-ends as raw materials; cyano polymer is prepared by polymerizing butyl acrylate and acrylonitrile with 4,4-azobis(4-cyanopentanol); and organosilicon block copolymer is prepared by copolymerization reaction of isocyanate silicone oil and cyano polymer.

[0013] The significant advantages of this invention compared to the prior art are: (a) With the bonding agent polymer side group containing amide groups and organosilicon precursors that can adsorb with oxidants, the block copolymer has excellent surface migration properties and is very easy to wet and spread into a film on the surface of oxidant solid particles in the composite solid propellant when in contact with the surface of the particles.

[0014] (b) The introduction of active groups such as hydroxyl groups into the molecular structure of block copolymer bonding agents can react with isocyanate-based curing agents in propellant formulations. Combined with the polymer's own coating of oxidant particles, a "toughening coating layer" can be formed on the surface of solid oxidant particles. This is the principle behind its bonding properties and prevention of propellant grain "dewetting".

[0015] (c) Organic block copolymer bonding agents have excellent high and low temperature characteristics, that is, their mechanical properties change slowly with temperature. They will not become sticky at high temperatures or brittle at low temperatures. When introduced into the molecular structure of block copolymer bonding agents, they can form a "toughening" layer on the surface of the oxidant in solid propellants. This can combine the multi-point physical adsorption with the strong flexibility of the organosilicon molecular chain, thereby improving the high temperature mechanical properties of composite solid propellants. Attached Figure Description

[0016] Figure 1 This is a hydrogen nuclear magnetic resonance image of the block copolymer type bonding agent prepared according to Example 1 of the present invention.

[0017] Figure 2 This is the infrared spectrum of the block copolymer bonding agent prepared according to Example 1 of the present invention.

[0018] Figure 3 This is a gel permeation chromatogram of the block copolymer bonding agent prepared according to Example 1 of the present invention.

[0019] Figure 4 To prepare solid propellant grains using the bonding agent prepared in Example 2 of this invention and according to Example 3, the percentage content of various elements on the surface of the oxidant particles was measured by EDS. Detailed Implementation

[0020] The specific preparation of the organosilicon block copolymer of the present invention is as follows: (1) Synthesis of isocyanate with two heads By weight, dissolve 10-80 parts of amino double-ended head and 2-30 parts of organic base in 10-80 parts of dehydrated toluene and place in a dropping device; Add 1-20 parts solid phosgene and 10-80 parts toluene to the reactor and cool to -20℃ to -10℃. Add the mixture of amino double-headed compound and organic base dropwise. After the addition is complete, start heating and control the temperature at 40-105℃. React at this temperature for 1-10 hours. After the reaction is complete, filter the solution; after the solvent is removed by evaporation of the filtrate, seal the remaining liquid and let it stand for 1 to 7 days, then distill it under reduced pressure to obtain the target product, isocyanate double-headed product.

[0021] (2) Ring-opening polymerization to produce silicone oil By weight, 20–500 parts of cyclosiloxane monomer, 2–20 parts of isocyanate double-ended head, and 0.1–5 parts of trifluoromethanesulfonic acid are added to a reactor; the temperature is raised to 40–100°C and the reaction is maintained for 1–10 hours; after the reaction is completed, 0.1–5 g of triethylamine is added to neutralize the reaction for 10 minutes to 5 hours; after the reaction is stopped, the mother liquor is removed by rotary evaporation under reduced pressure to remove the low fractions, yielding a viscous and transparent isocyanate silicone oil product.

[0022] (3) Preparation of cyano polymers by free radical polymerization By weight, 1 to 5 parts of 4,4-azobis(4-cyanopentanol) are dissolved in 10 to 100 parts of ethyl acetate to obtain an initiator solution; By weight, add 100-300 parts of butyl acrylate, 50-100 parts of acrylonitrile, 200-800 parts of ethyl acetate, and 1-20 parts of 2-mercaptoethanol to the reactor; after purging with nitrogen, raise the temperature to 50-90°C and add the initiator solution dropwise; control the dropping rate so that the reaction solution temperature does not exceed 90°C; after the addition is complete, keep the reaction at this temperature for 1-24 hours. After the reaction was completed, the solvent and unreacted monomers were removed from the reaction solution under reduced pressure to obtain a hydroxyl-terminated carbon chain cyano polymer.

[0023] (4) Coupling copolymerization reaction By weight, 100-500 parts of cyanopolymer are added to the reactor, heated to 50-120°C, and stirred and dehydrated for 30 minutes to 5 hours; 5-30 parts of isocyanate-based silicone oil and 0.005-0.05 parts of dibutyltin dilaurate are added; after reacting at this temperature for 1-8 hours, the product is obtained by cooling, which is an organosilicon block copolymer.

[0024] In the above technical solution, the organic base mentioned in the isocyanate double-heading synthesis step is pyridine or triethylamine; the vacuum distillation conditions are 80-150℃, preferably 110-120℃.

[0025] In the above technical solution, the cyclosiloxane monomer mentioned in the ring-opening polymerization step for producing silicone oil is one of D3, D4, or DMC.

[0026] This invention discloses the application of the above-mentioned organosilicon block copolymer type bonding agent in composite solid propellants, especially its application in improving the high-temperature mechanical properties of solid propellant grains.

[0027] The synthetic reaction formula and intermediate products of the organosilicon block copolymer disclosed in this invention are as follows: ; p=2~50; q=2~50; m= 4~100; n= 1~10.

[0028] The present invention will be further described below with reference to the embodiments and accompanying drawings. The raw materials used in the present invention are existing products, the specific preparation operations and performance tests are conventional techniques, and the dropwise addition is a conventional experimental operation. Example 1

[0029] (1) Synthesis of isocyanate with two heads

[0030] Preparation of the double-ended head: 46.6 g of amino double-ended head (1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane) and 10 g of triethylamine were dissolved in 40 g of dehydrated toluene and placed in a dropping funnel; Add 7.8 g of solid phosgene dissolved in 40 g of toluene solution to a 200 mL three-necked flask, and cool in an ice-water bath for 10 minutes; Then the mixture of amino double-headed and triethylamine was added dropwise to the three-necked flask. After the addition was complete, the temperature was raised to 60°C and the reaction was carried out at a constant temperature for 3 hours. After the reaction was complete, the mixture was filtered. The residue was light blue granular, and the filtrate was transparent yellow. The filtrate was fractionally distilled, and the solvent toluene was collected. The remaining liquid was placed in a sealed glass bottle and allowed to stand for 2 days. Then, the light yellow liquid was distilled under reduced pressure at 114–117 °C and 715 Pa. The fraction containing the target product was collected to obtain the product, a double-ended isocyanate, also known as 1,3-bis(3-isocyanatepropyl)-1,1,3,3-tetramethyldisiloxane, 35.3 g. The intermediate was tested using hydrogen NMR. 1 H NMR (300 MHz, CDCl3) δ 3.76 (t, J =18.7 Hz, 4H, C H 2-NCO), 1.88 (t, J =6.5 Hz, 4H, Si-CH2C H 2), 1.56 (t, J =6.5 Hz, 4H, Si-C H 2), 0.10 (s, 12H, Si-C H 3).

[0031] (2) Ring-opening polymerization to produce silicone oil 244.6 g of cyclosiloxane monomer (DMC, a mixed cyclic form of dimethylcyclosiloxane), 7.2 g of isocyanate double-ended head, and 1.0 g of trifluoromethanesulfonic acid were added to the reactor at once; the temperature was then raised to 60 °C and maintained for 4 h; after the reaction was completed, 0.8 g of triethylamine was added for neutralization and the reaction was continued for 1 h; after the reaction was stopped, the mother liquor was removed by rotary evaporation under reduced pressure to remove low fractions and maintained for 1 h; the product was discharged to obtain 244.1 g of viscous and transparent isocyanate silicone oil product.

[0032] (3) Preparation of cyano polymers by free radical polymerization First, dissolve 3.280g of 4,4-azobis(4-cyanopentanol) (code ACP) in 80g of ethyl acetate for later use; A 1000 mL three-necked flask, equipped with a thermometer, dropping funnel, and reflux condenser, was used to add 172 g of butyl acrylate, 88 g of acrylonitrile, 430 g of ethyl acetate, and 5.12 g of 2-mercaptoethanol. After purging with nitrogen, the temperature was raised to 75 °C, and an ethyl acetate solution of ACP was added dropwise over 40 min (the reaction temperature should not exceed 90 °C). After the addition was complete, the reaction was maintained at this temperature for 5 h. After the reaction was completed, the solvent was removed from the reaction solution under reduced pressure at 50°C, and then the temperature was raised to 80°C to remove unreacted monomers under reduced pressure, yielding 230g of hydroxyl-terminated carbon chain cyano polymer.

[0033] (4) Coupling copolymerization reaction A 250mL three-necked flask was heated in an oil bath with electromagnetic stirring and equipped with a thermometer. One feeding port was sealed with a rubber stopper for material injection. 200.2g of the cyanopolymer prepared by the above free radical polymerization was added, and the mixture was heated to 85℃ and stirred for 60min to remove water. Then, 0.02g of dibutyltin dilaurate and 12.8g of isocyanate-based silicone oil prepared by ring-opening polymerization were added. The reaction was maintained at this temperature for 3 hours, then cooled to 60℃ and stirred for 1.5h to obtain 208.9g of the product, an organosilicon block copolymer. Elemental analysis of the product (%): C 75.12; O 14.28; N 8.50; Si 2.10.

[0034] 1.0 g of the product was dissolved in 99.0 g of toluene to prepare a toluene solution with a mass concentration of 1%. The surface tension of the solution was measured to be 31.3 mN / m.

[0035] See Figure 1 This is the 1H NMR spectrum of the organosilicon block copolymer prepared in this embodiment, measured using deuterated chloroform (CDCl3) as solvent and tetramethylsilane (TMS) as internal standard.

[0036] See appendix Figure 2 This is the infrared spectrum of the organosilicon block copolymer prepared in this embodiment, 3626 cm⁻¹. -1The absorption peak is the hydroxyl group contained in the bonding agent molecule, at 3405 cm⁻¹. -1 The absorption peak for the urethane (NH) group in the repeating unit is 2250 cm⁻¹. -1 The absorption peak is the cyano group contained in the bonding agent molecule, at 1734 cm⁻¹. -1 The characteristic absorption peak for the urethane group (-C=O) is at 1265 cm⁻¹. -1 The absorption peak of Si-CH3 in polysiloxane chains is 1063 cm⁻¹. -1 This is the Si-O absorption peak.

[0037] See appendix Figure 3 This is a gel permeation chromatogram of the organosilicon block copolymer prepared in this embodiment. Example 2

[0038] (1) Synthesis of isocyanate with two heads Preparation of double-ended head: 46.6 g of amino double-ended head (1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane) and 10 g of pyridine were dissolved in 40 g of dehydrated toluene and placed in a dropping funnel; Add 7.8 g of solid phosgene dissolved in 40 g of toluene solution to a 200 mL three-necked flask and cool it in an ice-water bath; then add dropwise a mixture of amino-double-headed and triethylamine. After the addition is complete, start heating and control the temperature at 60 °C. React at this temperature for 3 h. After the reaction was completed, the mixture was filtered. The residue was light blue granular, and the filtrate was transparent yellow. The filtrate was fractionally distilled, and the solvent toluene was collected. The remaining liquid was placed in a sealed glass bottle and allowed to stand for 2 days. The pale yellow liquid was then distilled under reduced pressure at 114–117 °C and 715 Pa, and the target product fraction was collected to obtain 33.0 g of the product isocyanate double-ended head.

[0039] (2) Ring-opening polymerization to produce silicone oil 244.6 g of octamethylcyclotetrasiloxane (D4), 7.2 g of isocyanate double-ended head, and 1.0 g of trifluoromethanesulfonic acid were added to the reactor at once; the temperature was raised to 60 °C and the reaction was maintained for 4 h; after the reaction was completed, 0.8 g of triethylamine was added for neutralization and the reaction was maintained for 1 h; after the reaction was stopped, the mother liquor was removed by rotary evaporation under reduced pressure to remove the low fractions and maintained for about 1 h; the product was discharged to obtain 243.9 g of viscous and transparent isocyanate silicone oil product.

[0040] (3) Preparation of cyano polymers by free radical polymerization First, dissolve 3.280g of 4,4-azobis(4-cyanopentanol) (code ACP) in 80g of ethyl acetate for later use.

[0041] A 1000 mL three-necked flask, equipped with a thermometer, dropping funnel, and reflux condenser, was filled with 172 g of butyl acrylate, 88 g of acrylonitrile, 432 g of ethyl acetate, and 6.16 g of 2-mercaptoethanol. After purging with nitrogen, the mixture was heated to 70 °C, and an ethyl acetate solution of ACP was added dropwise. The dropping rate was controlled to prevent excessive heating (the reaction is exothermic), and the addition was completed over 40 minutes, with the reaction temperature not exceeding 90 °C. After the addition was complete, the reaction was maintained at this temperature for 5 hours.

[0042] The solvent was removed from the reaction solution under reduced pressure at 50°C, and then the temperature was raised to 80°C to remove unreacted monomers under reduced pressure, yielding 212g of hydroxyl-terminated carbon chain cyano polymer.

[0043] (4) Coupling copolymerization reaction A 250mL three-necked flask was heated in an oil bath with electromagnetic stirring and equipped with a thermometer. The other feeding port was sealed with a rubber stopper for material injection. 160.4g of the cyano polymer prepared by the above free radical polymerization was added, and the mixture was heated to 85℃ and stirred to dehydrate for 60min. Then, 0.02g of dibutyltin dilaurate and 14.6g of isocyanate-based silicone oil prepared by ring-opening polymerization were added. The reaction was kept at this temperature for 3 hours, then cooled to 50-60℃ and stirred for 1.5h. After cooling, 168.9g of the product, an organosilicon block copolymer, was obtained.

[0044] 1.0 g of the product was dissolved in 99.0 g of toluene to prepare a toluene solution with a mass concentration of 1%. The surface tension of the solution was measured to be 27.6 mN / m.

[0045] Comparative Example 1 (1) Prepare cyano polymers according to the same process as in Example 1.

[0046] (2) Chain extension reaction A 250mL three-necked flask was heated in an oil bath with electromagnetic stirring and equipped with a thermometer. One feeding port was sealed with a rubber stopper for material injection. 200.5g of the cyanopolymer prepared above was added. The mixture was heated to 85℃ and stirred to remove water for 60min. Then, 0.02g of dibutyltin dilaurate and 12.9g of isoflurane diisocyanate were added. The reaction was maintained at this temperature for 3 hours, then cooled to 50–60℃ and stirred for 1.5h. After cooling, 206.1g of the product was obtained. 1.0g of the product was dissolved in 99.0g of toluene to prepare a 1% (w / w) toluene solution. The surface tension of the solution was measured to be 38.9 mN / m.

[0047] Example 3: Application of bonding agents in composite solid propellant formulations The prepared organosilicon block copolymer was added as a bonding agent to the formulation of a hydroxyl-butadiene tetra-component composite solid propellant. The tetra-component propellant formulation contained two oxidants: ammonium perchlorate (AP) and nitramine oxidant (RDX). The different propellant compositions were: 15g hydroxyl-butadiene rubber, 0.3g cattocin (burning rate catalyst), 65g ammonium perchlorate, 19g nitramine oxidant (RDX), and 0.1g of the prepared bonding agent. After mixing in a kneader for 1 hour, 3g of isoflurane diisocyanate (curing agent) was added, and mixing continued for 30 minutes. The mixture was then poured in a conventional manner and cured at 60°C for 7 days.

[0048] The mechanical properties of the drug column obtained by the bonding agent in Example 1 were tested. The tensile strength (σ) at room temperature (23℃) and high temperature (70℃) was 915kPa and 687kPa, respectively, and the elongation at break at room temperature and high temperature was 70.1% and 56.4%, respectively, which are significantly better than existing macromolecular bonding agents. Figure 4 The measured contents of C, O, N, and Si on the surface of the oxidant particles were 71.05%, 13.96%, 9.74%, and 3.57%, respectively. The Si content was significantly higher than the average silicon content of the block copolymer bonding agent itself. This indicates that the organosilicon block copolymer of this invention exhibits excellent migration capabilities when applied to solid propellant bonding.

[0049] In Example 2, the mechanical properties of the drug column obtained by the bonding agent were tested. The tensile strength (σ) at room temperature and high temperature (70°C) was 1110 kPa and 801 kPa, respectively, and the elongation at break at room temperature and high temperature was 78.1% and 61.4%, respectively.

[0050] The mechanical properties of the drug column obtained by the comparative one-bonding agent were tested. The tensile strength (σ) at room temperature and high temperature (70℃) was 533kPa and 387kPa, respectively, and the elongation at break at room temperature and high temperature was 27.2% and 30.9%, respectively.

[0051] Comparison Example A hydroxyl-butadiene (HbA1c) tetrone composite solid propellant column was prepared without adding a bonding agent: 15g HbA1c; 0.3g cattoxin (burning rate catalyst); 65g ammonium perchlorate; and 19.1g RDX (nitramine oxidant). The mixture was kneaded for 1 hour, then 3g isoflurane diisocyanate (curing agent) was added, and mixing continued for 30 minutes. The column was then cast using standard methods and cured at 60℃ for 7 days. The mechanical properties of the resulting column were tested. The tensile strength (σ) at room temperature (23℃) and high temperature (70℃) was 428kPa and 330kPa, respectively, and the elongation at break at room temperature and high temperature was 18.6% and 11.2%, respectively.

[0052] According to reports, when using the traditional small-molecule bonding agent tris(aziridine)phosphine oxide (MAPO) to bond hydroxyl propellants, their mechanical strength at room temperature is generally between 400 kPa and 520 kPa, and their mechanical strength at high temperature is generally between 250 kPa and 350 kPa. The bonding agent provided by this invention can provide higher mechanical strength, especially high-temperature mechanical strength, and significantly improved elongation at break.

[0053] When the bonding agent of this invention is applied to a composite propellant system filled with ammonium perchlorate (AP) and nitramine oxidizer, it exhibits the property of migrating to the surface of oxidizer particles in the propellant slurry, forming an interfacial film between the oxidizer and the binder. The bonding agent of this invention neither becomes sticky at high temperatures nor brittle at low temperatures. Introducing it into the molecular structure of a block copolymer bonding agent allows it to form a "toughening" layer on the oxidizer surface in the solid propellant, organically combining multi-point physical adsorption with the strong flexibility of the organosilicon molecular chain. In particular, the block copolymer of this invention has the inherent characteristic that its mechanical properties are minimally affected by temperature changes. Therefore, even under high-temperature conditions, the "toughening" layer of the bonded solid propellant grain is not easily damaged or "dehydrated," thus the bonding agent of this invention is highly effective in improving the high-temperature mechanical properties of composite solid propellants.

Claims

1. A bonding agent, characterized in that, The bonding agent is an organosilicon block copolymer with the following structure: ； Where X is 4-cyanopentyl; p = 2–50; q = 2–50; m = 4–100; n = 1–10.

2. The method for preparing the bonding agent according to claim 1, characterized in that, The process includes the following steps: reacting a cyano polymer and an isocyanate-based silicone oil to obtain the organosilicon block copolymer; The chemical structural formula of the cyano polymer is as follows: ； The chemical structural formula of the isocyanate-based silicone oil is as follows: 。 3. The method for preparing the bonding agent according to claim 2, characterized in that, The reaction was carried out under the catalysis of organotin compounds; the reaction temperature was 50–120 °C and the time was 1–8 hours.

4. The method for preparing the bonding agent according to claim 3, characterized in that, The mass ratio of cyanopolymer, isocyanate-based silicone oil, and organotin compound is (100-500): (5-30): (0.005-0.05).

5. The method for preparing the bonding agent according to claim 2, characterized in that, Isocyanate-based silicone oil was prepared using cyclosiloxane monomers and isocyanate double-ended heads as raw materials; cyanopolymer was prepared by polymerization reaction using 4,4-azobis(4-cyanopentanol) as an initiator and butyl acrylate and acrylonitrile as raw materials; the isocyanate double-ended head was 1,3-bis(3-isocyanatepropyl)-1,1,3,3-tetramethyldisiloxane.

6. The method for preparing the bonding agent according to claim 5, characterized in that, When preparing isocyanate-based silicone oil, methanesulfonic acid compound is used as catalyst; the polymerization reaction temperature is below 90℃ and the time is 1 to 24 hours.

7. A composite solid propellant, comprising an oxidant and a binder, characterized in that, It also includes the organosilicon block copolymer of claim 1 as a bonding agent.

8. The application of the bonding agent of claim 1 in solid propellants.

9. The application according to claim 8, characterized in that, The bonding agent improves the mechanical properties of the solid propellant.

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