Application of HTPB-based sensing film in monitoring of migration volume of nitroglycerin in propellant

Abstract

The invention discloses an application of an HTPB-based sensing film in monitoring the migration volume of nitroglycerin in a propellant. The HTPB-based sensing film is obtained by using a multi-walled carbon nanotube as a conductive filler, HTPB as a binder matrix and toluene as a solvent through a solution blending method. The HTPB-based sensing film prepared by the invention is adhered to the surface of a double-base propellant, and the migration amount of nitroglycerin in the propellant is reflected through the change of conductivity, so that the real-time monitoring of the migration of the nitroglycerin in the propellant is realized. The HTPB-based sensing film disclosed by the invention is small and light, and can be transported along with a propellant to go through the same environment, so that a detection result is real and reliable.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of non-destructive monitoring of the health state of solid propellant, and relates to application of an HTPB-based sensing film in monitoring the migration amount of nitroglycerin in propellant. BACKGROUND

[0002] During the aging process of nitroglycerin-containing propellant, nitroglycerin migrates, thereby affecting the service life of the engine charge. Therefore, in order to ensure that the propellant can obtain the maximum economic benefit during service, structural health monitoring technology emerges as the times require. At present, the research object of propellant structural health monitoring is mostly HTPB-based solid propellant, and there are few studies on the migration amount of nitroglycerin in nitroglycerin-containing propellant or double-base propellant. Jia-ming Liu et al. measured and analyzed the changes in the content of N-methyl-4-nitroaniline (MNA) and the maximum elongation of propellant at different thermal aging temperatures (323.15 K, 333.15 K, 343.15 K and 353.15 K), proposed an improved CMDB propellant index aging model, and used the modified Arrhenius equation to predict the storage life of CMDB propellant at 298.15 K by taking the content of MNA and the maximum elongation as aging indicators. According to the estimation of the content of MNA and the maximum elongation, the storage life of CMDB at 298.15 K is 20.84 years and 19.19 years, respectively (Jia-ming Liu, Tian-yi Li, Ming-feng Yang, et, al. Storage-life prediction and relationship between maximum elongation and stabilizer depletion for a composite modified double base propellant (CMDB) propellant. Mechanics of Time-Dependent Materials, 2023). Liu Jiaming et al. conducted gas chromatography experiments on CMDB propellant samples with different aging times (0, 10, 20, 35, 50, 65, 80, 100 d), and studied the changes in the mechanical properties and the content of central stabilizer of the aged CMDB propellant. According to the significant downward trend of the maximum elongation and the content of central stabilizer during the aging process, they can be used as failure criteria for the aged CMDB propellant (Liu Jiaming, Xu Jingsheng, Chen Xiong, et. al. Tensile mechanical properties and strength master curve of thermal aging modified double-base propellant. Energetic Materials, 2021). SUMMARY

[0003] The purpose of this invention is to provide an application of hydroxyl-terminated polybutadiene (HTPB) sensing film in monitoring the migration of nitroglycerin in propellants. The HTPB-based film containing conductive filler is used as a sensing film to monitor the migration of nitroglycerin during the aging process of propellants containing nitroglycerin, thereby achieving real-time monitoring of the migration of nitroglycerin during the aging process.

[0004] The technical solution for achieving the objective of this invention is as follows:

[0005] The specific steps for applying HTPB-based sensing films to monitor the migration of nitroglycerin in propellants are as follows:

[0006] Step 1, Preparation of HTPB-based sensing film:

[0007] (1) Preparation of precursor solution: Hydroxyl-terminated polybutadiene (HTPB), 1,4-butanediol (BDO) and dibutyltin dilaurate (DBTDL) were added to toluene and stirred to mix them evenly to obtain the precursor solution.

[0008] (2) Preparation of conductive filler dispersion: Multi-walled carbon nanotubes (MWCNTs) were added to toluene and ultrasonically stirred to disperse them evenly, thus obtaining a conductive filler dispersion.

[0009] (3) Preparation of sensing film: The precursor solution and conductive filler dispersion were mixed, isophorone diisocyanate (IPDI) was added, magnetic stirring was performed, the mixture was allowed to stand, poured into a mold, vacuumed and heated until the sample was completely dried to obtain HTPB-based sensing film (HTPB-MWCNTs).

[0010] Step 2: Fix the HTPB-based sensing film containing conductive filler onto the surface of the propellant containing nitroglycerin, monitor its conductivity, and calculate the amount of nitroglycerin migration during the aging process of the propellant by fitting a curve based on the relationship between conductivity and nitroglycerin migration, thereby realizing real-time monitoring of nitroglycerin migration during the aging process.

[0011] Preferably, in step 1(1), the molar ratio of HTPB to 1,4-butanediol is 1:0.2.

[0012] Preferably, in step 1(1), the mass of DBTDL is 0.05% of the total mass of HTPB, 1,4-butanediol and IPDI, and the stirring time is 1 to 2 hours.

[0013] Preferably, in step 1(2), the mass of MWCNTs is 4% of the total mass of HTPB, 1,4-butanediol and IPDI, and the ultrasonic stirring time is 30-50 min.

[0014] Preferably, in step 1(3), the molar ratio of HTPB to IPDI functional groups is 1:1.

[0015] Preferably, in step 1(3), the vacuum is drawn to -0.09MPa, dried at 80℃ for 12h, and then the temperature is raised to 120℃ for 4h.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This invention prepares an HTPB-based sensing film using a solution blending method, which is simple and convenient. The HTPB-based sensing film is small and lightweight, and can be adhered to the propellant surface for transport, undergoing the same storage environment as the propellant. This invention uses a 71°C high-temperature aging test to monitor the relationship between the change in the conductivity of the sensing film and the migration of nitroglycerin in the propellant in real time. The test error is as low as 2.24%, and the test results are reliable, reducing the risks associated with propellant aging. This invention establishes a correlation between the conductivity of the sensing film and the migration of nitroglycerin in the double-base propellant during high-temperature aging to monitor the nitroglycerin content in the propellant in real time. Attached Figure Description

[0018] Figure 1 Image of HTPB-MWCNTs sample.

[0019] Figure 2 This is a schematic diagram of the HTPB-MWCNTs sample detection.

[0020] Figure 3 The relationship between conductivity and TG weight loss of HTPB-MWCNTs after 14 days of aging was simulated. Detailed Implementation

[0021] The present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0022] Example 1

[0023] (1) Preparation of precursor solution: Hydroxyl-terminated polybutadiene, 1,4-butanediol and dibutyltin dilaurate were added to toluene and magnetically stirred to make them evenly mixed.

[0024] (2) Preparation of conductive filler dispersion: Multi-walled carbon nanotubes were added to toluene and ultrasonically stirred for 30 minutes to disperse them evenly. The water in the water tank was changed every 10 minutes during this process to prevent the multi-walled carbon nanotubes from agglomerating due to overheating caused by ultrasonication.

[0025] (3) Preparation of HTPB-based sensing film: After the precursor solution and conductive filler dispersion are mixed evenly, isophorone diisocyanate is added, magnetic stirring is carried out for 4 hours, and after standing, it is poured into a mold, vacuumed to -0.09 MPa, dried at 80℃ for 12 hours, and then heated to 120℃ for 4 hours to obtain HTPB-based sensing film.

[0026] (4) Monitoring of propellant conductivity during high-temperature aging:

[0027] The HTPB-based sensing film was adhered to the surface of the propellant and placed in an oven to dry at 60°C for 12 hours to ensure complete adhesion of the HTPB-based sensing film to the propellant surface.

[0028] The resistance of the sensing film aged at 71℃ for different aging days was measured using a TH2686N leakage current tester. The specific implementation method is as follows: Figure 2 As shown in the figure. The sample size is 20*5.5*1mm. 3 The electrode spacing is 10mm, and according to the formula... The conductivity is calculated, where σ is the sample conductivity, L is the electrode spacing, R is the sample resistance, and S is the sample cross-sectional area.

[0029] Figure 3 The results show the aging of HTPB-based sensing films containing CNTs at 71℃ for 14 days. With increasing aging time, the sample conductivity decreased from 4.953 × 10⁻⁶. -3 Ω -1 ·cm -1 Decreased to 1.292*10 -3 Ω -1 ·cm -1 Meanwhile, the migration of nitroglycerin in the sensing film increased from 2.20 wt.% to 7.99 wt.%. Plotting the change in conductivity against the migration of nitroglycerin revealed a linear relationship, with the corresponding linear equation being: y = -1613.66x + 9.93, and a correlation coefficient r. 2 =0.96046. Therefore, the amount of nitroglycerin migration in the propellant can be monitored in real time based on the change in conductivity of the sensing film during the aging process.

[0030] Comparative Example 1

[0031] This comparative example is largely the same as Example 1, except that the conductive filler is carbon black (CB). Testing showed that as the voltage (5–15 kV) increased, the sample current remained unchanged at 1 nA, making it impossible to calculate the conductivity of the sensing film.

[0032] Comparative Example 2

[0033] This comparative example is largely the same as Example 1, except that the conductive filler is graphene (GP). Tests and calculations showed that the conductivity of the HTPB-based sensing film containing graphene was 5.924 × 10⁻⁶. -8 Ω -1 ·cm -1However, considering that the conductivity of the sensing film will decrease due to the migration of nitroglycerin during subsequent aging tests, it cannot be used as a sensing film to monitor the amount of nitroglycerin migration during the aging process of propellants containing nitroglycerin.

Claims

1. The application of HTPB-based sensing films in monitoring the migration of nitroglycerin in propellants, characterized in that, The specific steps are as follows: Step 1, Preparation of HTPB-based sensing film: (1) Preparation of precursor solution: HTPB, 1,4-butanediol and dibutyltin dilaurate were added to toluene and stirred to mix them evenly to obtain precursor solution; (2) Preparation of conductive filler dispersion: Multi-walled carbon nanotubes were added to toluene and ultrasonically stirred to disperse them evenly, thus obtaining conductive filler dispersion; (3) Preparation of sensing film: Mix the precursor solution and conductive filler dispersion, add isophorone diisocyanate, stir magnetically, let stand, pour into mold, vacuum and heat until the sample is completely dry to obtain HTPB-based sensing film. Step 2: Fix the HTPB-based sensing film containing conductive filler onto the surface of the propellant containing nitroglycerin, monitor its conductivity, and calculate the amount of nitroglycerin migration during the aging process of the propellant by fitting a curve based on the relationship between conductivity and nitroglycerin migration, thereby realizing real-time monitoring of nitroglycerin migration during the aging process.

2. The application according to claim 1, characterized in that, In step 1 (1), the molar ratio of HTPB to 1,4-butanediol is 1:0.

2.

3. The application according to claim 1, characterized in that, In step 1 (1), the mass of dibutyltin dilaurate is 0.05% of the total mass of HTPB, 1,4-butanediol and isophorone diisocyanate, and the stirring time is 1~2h.

4. The application according to claim 1, characterized in that, In step 1 (2), the mass of the multi-walled carbon nanotubes is 4% of the total mass of HTPB, 1,4-butanediol and isophorone diisocyanate, and the ultrasonic stirring time is 30~50 min.

5. The application according to claim 1, characterized in that, In step 1 (3), the molar ratio of HTPB to isophorone diisocyanate functional groups is 1:

1.

6. The application according to claim 1, characterized in that, In step 1 (3), the vacuum is drawn to -0.09MPa, dried at 80℃ for 12h, and then the temperature is raised to 120℃ for 4h.

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