A method for preparing a dual crosslinking propellant liner resistant to small molecule migration

Abstract

The application discloses a preparation method of a double-crosslinking propellant lining resistant to small molecule migration, and belongs to the field of composite material preparation. In the application, graphene oxide is used as a nano filler, and toluene diisocyanate is used as a modifier, so that the chemical grafting of isocyanate groups on the surface of the graphene oxide is realized in a water-free DMF solution. By grafting isocyanate groups on the surface of the graphene oxide, the polar groups on the surface of the graphene oxide are reduced, the graphene oxide filler is better dispersed in the matrix material, and a multiple crosslinking structure is promoted, so that the anti-migration performance of the propellant lining is improved. The preparation process is simple, and the modification process of the graphene oxide is controllable.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation, and specifically relates to a method for improving the anti-migration properties of modified graphene oxide in propellant liner. Background Technology

[0002] During long-term storage, external factors such as temperature, humidity, and light can cause the migration of small molecules in propellants, including nitroglycerin and energetic plasticizers. The continuous migration of plasticizers from the propellant grain directly leads to grain shrinkage, coating swelling, and disruption of the interfacial bond between the propellant and coating. This significantly reduces interfacial adhesion strength, making debonding more likely and potentially causing accidents. Therefore, we need a material that can both tightly bond the propellant and coating and possess excellent anti-migration properties. Propellant liners were developed to meet this need. However, with the continuous development of high-energy solid propellants, the performance requirements for liners are constantly increasing, and modifications to liner materials are being proposed. Adding nanofillers has become a mainstream approach in many studies.

[0003] The high aspect ratio and high electron cloud density of graphene oxide (GO) carbon rings enable it to impede the penetration of atoms and molecules, thus making it a promising nanomaterial for barrier applications. The numerous oxygen-containing groups on the GO surface provide more active sites for material modification and preparation. Recent studies have shown that GO exhibits excellent barrier effects in polymer composites. For example, Zheng et al. (Zheng L, Jerrams S, Xu Z, et al. Enhanced gas barrier properties of graphene oxide / rubber composites with strong interfaces constructed by graphene oxide and sulfur[J]. Chemical Engineering Journal,2020, 383:599-608.) constructed a robust interface and filler network by introducing GO into styrene-butadiene rubber (SBR). The composite filler network and strong interfacial interactions significantly reduced the free volume between SBR molecules, prolonging the molecular path and diffusion time in the matrix, thereby achieving high barrier performance. However, by modifying GO, both the composite crosslinking network of the liner and the dispersibility of GO in the matrix can be improved, thus exhibiting good resistance to small molecule migration. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the anti-migration performance of propellant liners. This is achieved by modifying GO in anhydrous DMF solution, reducing its surface polar groups, and grafting isocyanate groups, allowing the modified GO to be better dispersed in the matrix, thereby improving the anti-migration performance of the propellant liner. This preparation method is simple, the GO modification process is controllable, and it is an effective way to improve the anti-migration performance of propellant liners.

[0005] This invention is achieved using the following technical solution:

[0006] A method for improving the anti-migration performance of propellant liners specifically includes the following steps:

[0007] Step 1: GO is prepared using the modified Hummers method;

[0008] Step 2: Place the dried GO from Step 1 into anhydrous DMF solution, add toluene diisocyanate and dibutyltin dilaurate (DBTL), and perform graft modification at 75-85℃ for 4-6 hours. Wash and dry to obtain modified GO.

[0009] Step 3: Disperse the modified GO from Step 2 in an organic reagent, place it in a hydroxyl-terminated polybutadiene (HTPB) matrix, stir evenly, and keep warm to remove the organic solvent. Add plasticizer, toluene diisocyanate (TDI), and catalyst dibutyltin dilaurate and react for 2-3 hours. Add triethanolamine (TEA), stir evenly, and pour into a mold for vacuum curing to obtain the propellant liner.

[0010] Preferably, in step two, the grafted tissue is washed with N,N-dimethylformamide and deionized water.

[0011] Preferably, in step two, the amount of dibutyltin dilaurate used is 1‰ of the mass of GO.

[0012] Preferably, in step three, the concentration of the organic solvent dispersion of modified GO is 1 mg / mL, which is obtained by ultrasonically dispersing the modified GO in acetone for 1-2 hours.

[0013] Preferably, in step three, the plasticizer is dioctyl sebacate (DOS); the mass ratio of DOS to HTPB is 1:20, the mass ratio of HTPB to DBTL is 1:0.001, and the mass ratio of TEA to HTPB is 0.03:1; toluene diisocyanate is added dropwise according to the curing coefficient R=1.3, and the reaction is carried out under a nitrogen atmosphere for 2-3 hours; after adding TEA and stirring for 1-3 minutes, it is poured into a mold and vacuum cured for 48 hours.

[0014] Preferably, the modified GO content in the propellant liner is 0.1-0.3 wt%.

[0015] Preferably, in steps two and four, the toluene diisocyanate is 2,4-toluene diisocyanate.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] (1) This invention improves the layered three-dimensional structure and surface roughness of GO by chemically grafting isocyanate groups onto the surface and reducing the polar groups on its surface, thereby reducing surface polarity. The modified GO can better bond with the matrix, thus effectively improving the anti-migration performance of the propellant liner. (2) When the concentration of the modified GO dispersion solution is 1 mg / mL, the modified GO can be uniformly dispersed in the organic reagent. Adding it to the matrix material can help it disperse in the matrix, thus preparing a propellant liner with a more compact structure. At this time, the migration equilibrium concentration of the propellant liner reached 52.24%, which is 32.25% higher than the 77.11% of the sample without GO filler and 11.69% higher than the 59.16% of the sample without modified GO filler, both of which are significant improvements. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the dispersion of GO prepared in Example 1 and Comparative Example 1 of the present invention.

[0019] Figure 2 The images shown are scanning electron microscope (SEM) images of GO prepared in Example 1 and Comparative Example 1 of this invention.

[0020] Figure 3 The XPS spectra of GO prepared in Example 1 and Comparative Example 1 of this invention are shown, where (a) is the full spectrum of GO; (b) is the carbon spectrum of GO; (c) is the full spectrum of modified GO; (d) is the carbon spectrum of modified GO; and (e) is the nitrogen spectrum of modified GO.

[0021] Figure 4 , 5 The graphs show the anti-migration properties of the propellant liner prepared in Examples 1-3 and Comparative Examples 1-2 of this invention.

[0022] Figure 6 The graphs show the bonding performance of the propellant liner prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to examples and accompanying drawings, but the present invention is not limited to these examples.

[0024] Example 1

[0025] Step 1: Pour 50 mL of 98% concentrated H₂SO₄ into a beaker. Weigh 2 g of graphite powder and 1 g of NaNO₃, and add them to the beaker, stirring. Weigh 6 g of KMnO₄ and add it to the flask in 6 portions, 20 min apart, controlling the reaction temperature at 0–10 °C. Raise the temperature to 35 °C and oxidize for 2 h. Add 100 mL of deionized water and maintain the temperature for another 2 h. Raise the temperature to 90 °C, add 200 mL of deionized water to dilute, and cool the solution by adding a small amount of 30% H₂O₂ until the solution turns bright yellow. Centrifuge to obtain the product, wash away the metal ions with dilute hydrochloric acid, wash with water until neutral, and dry. Label the product as graphene oxide.

[0026] Step 2: Weigh 0.2 g of GO to prepare a 1 mg / mL anhydrous N,N-dimethylformamide suspension, sonicate for 3 h, heat to 80 °C, slowly add 1 g of 2,4-toluene diisocyanate to the reaction solution, add 0.2 mg of dibutyltin dilaurate catalyst, and purge with nitrogen for 5 h. Centrifuge to obtain the product, wash away unreacted 2,4-toluene diisocyanate with N,N-dimethylformamide, dry, and label as TDI / GO.

[0027] Step 3: Weigh 39.95g of HTPB into a four-necked flask and place it in a vacuum drying oven at 100℃ for 3 hours to remove water. Weigh 0.0399g of modified GO to prepare an organic dispersion of 1mg / mL and sonicate for 1 hour. Pour the dispersion into the four-necked flask, stir evenly, and keep warm to remove the solvent. Weigh 1.9975g of dioctyl sebacate and 2.1614g of 2,4-toluene diisocyanate and add them dropwise to the reaction system. Add 0.039g of dibutyltin dilaurate and react under a nitrogen atmosphere for 3 hours. Weigh 1.1985g of triethanolamine and add it dropwise to the reaction system. Stir evenly and then stop the reaction.

[0028] Step four: The resulting slurry is poured into a mold and vacuum-cured in a vacuum drying oven for 48 hours to obtain the propellant liner. To test the anti-migration performance of the propellant liner, the cured liner is cut into 20×20×2mm pieces and immersed in a plasticizer solution to test its anti-migration performance, labeled as TDI-GO / HTPB. 0.1 .

[0029] Step 5, in order to test the propellant liner TDI-GO / HTPB 0.1 To test the bonding performance, two titanium alloy plates (100×25×1.5mm) were cleaned with anhydrous ethanol. The lining slurry obtained in step three was applied to the titanium alloy plate joint at a size of 25×12.5mm, clamped with dovetail clips, and placed in a vacuum drying oven. The plates were kept at 60℃ for 48 hours. The dovetail clips were then removed to obtain the bonding tensile test sample 1.

[0030] Example 2

[0031] Step 1: Pour 50 mL of 98% concentrated H₂SO₄ into a beaker. Weigh 2 g of graphite powder and 1 g of NaNO₃, and add them to the beaker, stirring. Weigh 6 g of KMnO₄ and add it to the flask in 6 portions, 20 min apart, controlling the reaction temperature at 0–10 °C. Raise the temperature to 35 °C and oxidize for 2 h. Add 100 mL of deionized water and maintain the temperature for another 2 h. Raise the temperature to 90 °C, add 200 mL of deionized water to dilute, and cool the solution by adding a small amount of 30% H₂O₂ until the solution turns bright yellow. Centrifuge to obtain the product, wash away the metal ions with dilute hydrochloric acid, wash with water until neutral, and dry. Label the product as graphene oxide.

[0032] Step 2: Weigh 0.2 g of GO to prepare a 1 mg / mL anhydrous N,N-dimethylformamide suspension, sonicate for 3 h, heat to 80 °C, slowly add 1 g of 2,4-toluene diisocyanate to the reaction solution, add 0.2 mg of dibutyltin dilaurate catalyst, and purge with nitrogen for 5 h. Centrifuge to obtain the product, wash away unreacted 2,4-toluene diisocyanate with N,N-dimethylformamide, dry, and label as TDI / GO.

[0033] Step 3: Weigh 39.07g of HTPB into a four-necked flask and place it in a vacuum drying oven at 100℃ for 3 hours to remove water. Weigh 0.0781g of modified GO to prepare an organic dispersion of 1mg / mL and sonicate for 1 hour. Pour the dispersion into a four-necked flask, stir until homogeneous, and keep warm to remove the solvent. Weigh 1.9535g of dioctyl sebacate and 2.1138g of 2,4-toluene diisocyanate and add them dropwise to the reaction system. Add 0.039g of dibutyltin dilaurate and react under a nitrogen atmosphere for 3 hours. Weigh 1.1721g of triethanolamine and add it dropwise to the reaction system. Stir until homogeneous and then stop the reaction.

[0034] Step four: The resulting slurry is poured into a mold and vacuum-cured in a vacuum drying oven for 48 hours to obtain the propellant liner. To test the anti-migration performance of the propellant liner, the cured liner is cut into 20×20×2mm pieces and immersed in a plasticizer solution to test its anti-migration performance, labeled as TDI-GO / HTPB. 0.2 .

[0035] Step 5, in order to test the propellant liner TDI-GO / HTPB 0.2 To test the bonding performance, two titanium alloy plates (100×25×1.5mm) were cleaned with anhydrous ethanol. The lining slurry obtained in step three was applied to the titanium alloy plate joint at a size of 25×12.5mm, clamped with dovetail clips, and placed in a vacuum drying oven. The plates were kept at 60℃ for 48 hours. The dovetail clips were then removed to obtain the bonding tensile test sample 2.

[0036] Example 3

[0037] Step 1: Pour 50 mL of 98% concentrated H₂SO₄ into a beaker. Weigh 2 g of graphite powder and 1 g of NaNO₃, and add them to the beaker, stirring. Weigh 6 g of KMnO₄ and add it to the flask in 6 portions, 20 min apart, controlling the reaction temperature at 0–10 °C. Raise the temperature to 35 °C and oxidize for 2 h. Add 100 mL of deionized water and maintain the temperature for another 2 h. Raise the temperature to 90 °C, add 200 mL of deionized water to dilute, and cool the solution by adding a small amount of 30% H₂O₂ until the solution turns bright yellow. Centrifuge to obtain the product, wash away the metal ions with dilute hydrochloric acid, wash with water until neutral, and dry. Label the product as graphene oxide.

[0038] Step 2: Weigh 0.2g of GO to prepare a 1mg / mL anhydrous N,N-dimethylformamide suspension, sonicate for 3 hours, heat to 80℃, slowly add 1g of 2,4-toluene diisocyanate to the reaction solution, add 0.2mg of dibutyltin dilaurate catalyst, and react under nitrogen for 5 hours. Centrifuge to obtain the product, wash away unreacted 2,4-toluene diisocyanate with N,N-dimethylformamide, dry, and label as TDI / GO.

[0039] Step 3: Weigh 34.00g of HTPB into a four-necked flask and place it in a vacuum drying oven at 100℃ for 3 hours to remove water. Weigh 0.102g of modified GO to prepare an organic dispersion of 2mg / mL and sonicate for 1 hour. Pour the dispersion into a four-necked flask, stir until homogeneous, and keep warm to remove the solvent. Weigh 0.9954g of dioctyl sebacate and 1.8395g of 2,4-toluene diisocyanate and add them dropwise to the reaction system. Add 0.034g of dibutyltin dilaurate and react under a nitrogen atmosphere for 3 hours. Weigh 1.0200g of triethanolamine and add it dropwise to the reaction system. Stir until homogeneous and then stop the reaction.

[0040] Step four: The resulting slurry is poured into a mold and vacuum-cured in a vacuum drying oven for 48 hours to obtain the propellant liner. To test the anti-migration performance of the propellant liner, the cured liner is cut into 20×20×2mm pieces and immersed in a plasticizer solution to test its anti-migration performance, labeled as TDI-GO / HTPB. 0.3 .

[0041] Step 5, in order to test the propellant liner TDI-GO / HTPB 0.3 To test the bonding performance, two titanium alloy plates (100×25×1.5mm) were cleaned with anhydrous ethanol. The lining slurry obtained in step three was applied to the titanium alloy plate joint at a size of 25×12.5mm, clamped with dovetail clips, and placed in a vacuum drying oven. The plates were kept at 60℃ for 48 hours. The dovetail clips were then removed to obtain the bonding tensile test sample 3.

[0042] Comparative Example 1

[0043] Step 1: Pour 50 mL of 98% concentrated H₂SO₄ into a beaker. Weigh 2 g of graphite powder and 1 g of NaNO₃, and add them to the beaker, stirring. Weigh 6 g of KMnO₄ and add it to the flask in 6 portions, 20 min apart, controlling the reaction temperature at 0–10 °C. Raise the temperature to 35 °C and oxidize for 2 h. Add 100 mL of deionized water and maintain the temperature for another 2 h. Raise the temperature to 90 °C, add 200 mL of deionized water to dilute, and cool the solution by adding a small amount of 30% H₂O₂ until the solution turns bright yellow. Centrifuge to obtain the product, wash away the metal ions with dilute hydrochloric acid, wash with water until neutral, and dry. Label the product as graphene oxide.

[0044] Step 2: Weigh 31.11g of HTPB into a four-necked flask and place it in a vacuum drying oven at 100℃ for 3 hours to remove water. Weigh 0.0933g of GO to prepare a 2mg / mL organic dispersion and sonicate for 1 hour. Pour the dispersion into the four-necked flask, stir until homogeneous, and keep warm to remove the solvent. Weigh 1.5555g of dioctyl sebacate and 1.6831g of 2,4-toluene diisocyanate and add them dropwise to the reaction system. Add 0.031g of dibutyltin dilaurate and react under a nitrogen atmosphere for 3 hours. Weigh 0.9333g of triethanolamine and add it dropwise to the reaction system. Stir until homogeneous and then stop the reaction.

[0045] Step 3: The resulting slurry is poured into a mold and vacuum-cured in a vacuum drying oven for 48 hours to obtain the propellant liner. To test the anti-migration performance of the propellant liner, the cured liner is cut into 20×20×2mm pieces and immersed in a plasticizer solution to test its anti-migration performance, labeled as GO / HTPB. 0.3 .

[0046] Step four, in order to test the propellant liner GO / HTPB 0.3 To test the bonding performance, two titanium alloy plates (100×25×1.5mm) were cleaned with anhydrous ethanol. The lining slurry obtained in step two was applied to the joint of the titanium alloy plate at a size of 25×12.5mm. The plates were clamped with dovetail clips and placed in a vacuum drying oven. The plates were kept at 60℃ for 48 hours. The dovetail clips were then removed to obtain the bonding tensile test sample 4.

[0047] Comparative Example 2

[0048] Step 1: Weigh 25.40g of HTPB into a four-necked flask and place it in a vacuum drying oven at 100℃ for 3 hours to remove water. Weigh 1.2700g of dioctyl sebacate and 1.3742g of 2,4-toluene diisocyanate and add them dropwise to the reaction system. Add 0.025g of dibutyltin dilaurate and react under a nitrogen atmosphere for 3 hours. Weigh 0.7620g of triethanolamine and add it dropwise to the reaction system. Stir until homogeneous and then stop the reaction.

[0049] Step two: The resulting slurry is poured into a mold and placed in a vacuum drying oven for vacuum curing for 48 hours to obtain the propellant liner. To test the anti-migration performance of the propellant liner, the cured liner is cut into small pieces of 20×20×2mm and immersed in a plasticizer solution to test its anti-migration performance, labeled as GO / HTPB0.

[0050] Step 3: To test the bonding performance of the propellant liner GO / HTPB0, two titanium alloy plates (100×25×1.5mm) were cleaned with anhydrous ethanol. The liner slurry obtained in Step 2 was applied to the 25×12.5mm joint of the titanium alloy plate, clamped with dovetail clips, and placed in a vacuum drying oven. The oven was kept at 60℃ for 48 hours. The dovetail clips were then removed to obtain the bonding tensile test sample 5.

[0051] Figure 1 Examples 1 and 1 (Comparative Example) of this invention show a comparison of the dispersibility of toluene diisocyanate-modified graphene oxide and untreated graphene oxide. As can be seen from the figures, the untreated graphene oxide dispersion exhibits significant sedimentation and stratification, while the modified graphene oxide dispersion shows no obvious particle sedimentation, demonstrating a stable and uniform dispersion. This indicates that the grafting modification of the graphene oxide surface introduces hydrophobic benzene rings and isocyanate groups, improving its hydrophobic properties and thus allowing for better dispersion in organic solvents.

[0052] Figure 2 Examples 1 and 1 Comparative Examples of the present invention are scanning electron microscope (SEM) images comparing the morphologies of toluene diisocyanate-modified graphene oxide and untreated graphene oxide. As can be seen from the images, untreated graphene oxide exhibits slight wrinkles and a distinct layered structure. After modification, the intercalation modification of isocyanate makes its layered structure more three-dimensional, the surface becomes uneven, and many wrinkles and defects can be found. The surface is covered with organic functional groups, and the particles are larger, which can more effectively block the pores through which small molecules pass.

[0053] Figure 3 Examples 1 and Comparative Example 1 of this invention show the XPS spectra of toluene diisocyanate-modified graphene oxide and untreated graphene oxide. The untreated graphene oxide has a relative C content of 65.4% and a relative O content of 34.6%. After grafting modification, the relative C content of the modified graphene oxide increased to 71.7%, and the relative O content decreased to 14.5%. The appearance of N indicates that toluene diisocyanate successfully modified the graphene oxide. After grafting isocyanate groups, the increase in the relative C content, the decrease in the relative O content, and the relative N content of 13.7% indicate that the isocyanate groups were successfully grafted onto the surface of the graphene oxide.

[0054] Figure 4 , 5 The graphs show the anti-migration properties of the propellant liners prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. Comparing Examples 1, 2, and 3 with Comparative Examples 1 and 2, it can be concluded that an appropriate amount of modified graphene oxide can achieve better anti-migration properties of the plasticizer. From Comparative Examples 1 and 2, it can be concluded that graphene oxide grafted with isocyanate groups has a significant impact on the anti-migration properties of the propellant liner.

[0055] Figure 6 The graphs show the bonding performance of the propellant liners prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. Comparing Examples 1, 2, and 3 with Comparative Examples 1 and 2 in the graphs, it can be concluded that an appropriate amount of modified graphene oxide can achieve better bonding strength.

[0056] In summary, this invention proposes a method to improve the anti-migration performance of propellant liners. It primarily utilizes the fact that isocyanate-grafted graphene oxide can better bond with the matrix, reducing the number of polar groups on its surface and promoting a tighter cross-linked network, thereby enhancing the anti-migration performance of the propellant liner. The preparation process of this invention is simple, the modification direction of graphene oxide is controllable, and it meets the requirements for effectively improving the anti-migration performance of composite liners. The experimental operation of this invention is simple and quick, the reagents used are economical, the operation process is controllable, and it can better improve the interfacial adhesion performance of the propellant liner.

Claims

1. A method for preparing a double-crosslinked propellant liner that resists small molecule migration, characterized in that, Specifically, the steps include the following: Step 1: GO is prepared using the modified Hummers method; Step 2: Place the dried GO from Step 1 into anhydrous DMF solution, add toluene diisocyanate and dibutyltin dilaurate, and perform graft modification at 75-85℃ for 4-6 hours. Wash and dry to obtain modified GO. Step 3: Disperse the modified GO from Step 2 in an organic solvent, place it in a hydroxyl-terminated polybutadiene matrix, stir evenly, keep warm to remove the organic solvent, add plasticizer, toluene diisocyanate and catalyst dibutyltin dilaurate dropwise and react for 2-3 hours, add triethanolamine, stir evenly and pour into a mold for vacuum curing to obtain the propellant liner.

2. The method as described in claim 1, characterized in that, In step two, the grafted tissue is washed with N,N-dimethylformamide and deionized water.

3. The method as described in claim 1, characterized in that, In step two, the amount of dibutyltin dilaurate used is 1 wt‰ of GO.

4. The method as described in claim 1, characterized in that, In step three, the concentration of the organic solvent dispersion of modified GO is 1 mg / mL, which is obtained by ultrasonically dispersing the modified GO in acetone for 1-2 hours.

5. The method as described in claim 1, characterized in that, In step three, the plasticizer is dioctyl sebacate; the mass ratio of dioctyl sebacate to hydroxyl-terminated polybutadiene is 1:20, the mass ratio of hydroxyl-terminated polybutadiene to dibutyltin dilaurate is 1:0.001, and the mass ratio of triethanolamine to hydroxyl-terminated polybutadiene is 0.03:1; toluene diisocyanate is added dropwise according to the curing coefficient R=1.3, and the reaction is carried out under a nitrogen atmosphere for 2-3 hours; after adding triethanolamine and stirring for 1-3 minutes, it is poured into a mold and vacuum cured for 48 hours.

6. The method as described in claim 1, characterized in that, The mass content of modified GO in the propellant liner is 0.1-0.3 wt%.

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