Aluminum-free clean propellant with low burning rate temperature sensitivity coefficient and preparation method thereof

Abstract

The present invention relates to the technical field of propellants, and specifically discloses an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient and a preparation method thereof. The aluminum-free clean propellant comprises, by mass percentage: binder: 9% - 15%; curing agent: 0.8% - 2%; oxidizer: 69% - 79%; plasticizer: 4% - 12%; combustion regulator: 0.5% - 2%; property regulator: 0.4% - 2%. Among them, the combustion regulator is a combination of copper and lead compounds and multi-walled carbon nanotubes. This propellant is a low burning rate temperature sensitivity coefficient propellant in a wide temperature range (-40°C to +50°C), with a burning rate temperature sensitivity coefficient not greater than 0.20% K-1. Moreover, the formulation has no metal powder, the product is clean, which reduces the design requirements for the performance of nozzle materials and nozzle structures. At the same time, it is of significant importance to the performance stability of solid rocket engines working for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of propellants, and particularly to an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient and a preparation method thereof. Background Art

[0002] The burning rate temperature sensitivity coefficient is one of the important performance indexes of solid propellants, which is defined as the change rate of the burning rate with the initial temperature under a constant pressure. It reflects the influence of the environmental temperature (i.e., the initial temperature) of the propellant on the burning rate of the solid propellant. The burning rate temperature sensitivity coefficient is an important parameter affecting the engine performance and an important factor for the engine performance to change with the environment. Even if the engine charge is a platform propellant with a pressure of zero, when the initial temperature changes from +50 °C to -40 °C, the combustion chamber pressure will also change by 18%. As a result, both the thrust and the burning time will change accordingly. Therefore, for some missile engines with harsh operating conditions, it is necessary to use a launch rack with a heat preservation device and an adjustable nozzle. For a propellant with a low temperature sensitivity coefficient, on the one hand, the burning rate changes very little within a certain temperature range, thus reducing the influence of the pressure and thrust fluctuations caused by environmental changes on the engine, which is beneficial to reducing the ballistic deviation and improving the shooting accuracy; on the other hand, it reduces the pressure fluctuations at different environmental temperatures, and can reduce the maximum design pressure of the engine, thereby reducing the structural mass coefficient of the engine. In order to enable a solid rocket engine to operate normally within a wide temperature range and have high working performance, designers at home and abroad hope that the burning rate temperature sensitivity coefficient of the solid propellant is as small as possible, and have listed the adjustment technology of the burning rate temperature sensitivity coefficient of the solid propellant as a key research topic.

[0003] The burning rate temperature sensitivity coefficient is an inherent property of the formulation and is a difficult problem in the industry. So far, the adjustment technology lacks systematic theoretical support and the adjustment means are limited. In the visible reports, there are mainly two adjustment ways for the burning rate temperature sensitivity coefficient. One is the chemical method, which is achieved by adding metal powders or catalysts and other substances to the formulation; the other is the physical method, which is mainly achieved by changing the particle size of the oxidizer. In order to reduce the burning rate temperature sensitivity coefficient, the most effective means for the current composite solid propellants is to greatly increase the content of metal powders. The metal powders include aluminum, magnesium, lithium, beryllium, boron, etc. Therefore, the combustion products contain metal oxides, which are extremely likely to cause deposition or erosion of the nozzle throat during the combustion process, resulting in ablation. If there is more deposition in the nozzle throat, the area of the nozzle throat will be irregularly reduced, causing thrust eccentricity and a sharp increase in pressure; while the ablation of the nozzle throat will also cause thrust eccentricity and a sharp drop in pressure. Both of these situations will have a serious impact on the engine performance. For example, Patent CN 105130720A introduces a propellant with a low burning rate temperature sensitivity coefficient, and its burning rate temperature sensitivity coefficient (the test temperature range is -30 °C to +40 °C) is not greater than 0.15% / K -1, but the formula contains 10% to 18% metal powder fuel. Due to the presence of more metal oxides in the combustion products, there is a problem of easy ablation or deposition in the nozzle throat, which is not suitable for solid rocket engines with long working time and low characteristic requirements. SUMMARY OF THE INVENTION

[0004] In view of the above problems, the first object of the present invention is to provide an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient. The propellant is a low burning rate temperature sensitivity coefficient propellant with a wide temperature range (-40℃~+50℃), and the burning rate temperature sensitivity coefficient is not more than 0.20%K -1 , and the formula does not contain metal powder, the product is clean, which reduces the design requirements of nozzle material performance and nozzle structure, and at the same time has a significant significance for the performance stability of solid rocket engines working for a long time.

[0005] The second object of the present invention is to provide a method for preparing an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient.

[0006] The first technical solution adopted by the present invention is: an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient, which includes the following components by mass percentage:

[0007] Binder: 9%~15%;

[0008] Curing agent: 0.8%~2%;

[0009] Oxidant: 69%~79%;

[0010] Plasticizer: 4%~12%

[0011] Combustion regulator: 0.5%~2%:

[0012] Performance regulator: 0.4%~2%;

[0013] Wherein, the combustion regulator is a combination of copper, lead compounds and multi-walled carbon nanotubes.

[0014] Preferably, the copper and lead compound is a mixture of lead benzoate and copper adipate, and the mass ratio of lead benzoate to copper adipate is 1:1.

[0015] Preferably, the mass percentage of the copper and lead compounds in the combustion regulator is in the range of 20% to 80%.

[0016] Preferably, the adhesive is ethylene oxide-tetrahydrofuran copolyether.

[0017] Preferably, the curing agent is a dimerized aliphatic diisocyanate.

[0018] Preferably, the oxidizer is a combination of ammonium perchlorate and 5,5'-bistetrazole-1,1'-dioxydihydroxylammonium salt.

[0019] Preferably, the average particle size of the ammonium perchlorate and 5,5'-bistetrazole-1,1'-dioxydihydroxylammonium salt is less than 15 μm.

[0020] Preferably, the plasticizer is one of butyl-nitroxyethyl nitramine, bis(2,2-dinitropropyl) formal, bis(2,2-dinitropropyl) acetal, and nitroglycerin.

[0021] Preferably, the performance regulator is a combination of triphenyl bismuth, lecithin, tris-1-(2-methylaziridine) phosphine oxide, and N-methyl-p-nitroaniline.

[0022] The second technical solution adopted in the present invention is: a preparation method of an aluminum-free clean propellant as described in the first technical solution, comprising the following steps:

[0023] S1: Weigh each component according to the mass percentage of each component in the aluminum-free clean propellant described in the first technical solution, add the combustion regulator and the performance regulator to the binder, add the plasticizer for premixing, and then add the oxidizer for mixing to obtain a premixed slurry;

[0024] S2: Add a curing agent to the premixed slurry and continue to mix evenly to obtain a slurry;

[0025] S3: Vacuum pour the slurry into a mold or an engine, and after curing, obtain an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient.

[0026] The beneficial effects of the above technical solutions:

[0027] (1) The aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient provided by the present invention has a low burning rate temperature sensitivity coefficient and is an aluminum-free clean propellant. It solves the problem of deposition or ablation at the nozzle throat starting from the formulation, which is particularly important for solid rocket engines with long working hours (working time greater than 100 s).

[0028] (2) Based on the combustion physical model of composite solid propellants, the surface temperature T s and the net heat of gasification σ p of the propellant during the combustion process are the main factors affecting the burning rate temperature sensitivity coefficient; the present invention uses copper and lead compounds as one of the combustion performance regulators. The decomposition products of copper and lead compounds participate in the pyrolysis of the carbon-based components in the formulation, generating a large amount of coke to cover the combustion surface, affecting the heat feedback from the flame zone, and keeping the surface temperature T s relatively stable, and the net heat of gasification σ prises, ultimately leading to a lower burning rate temperature sensitivity coefficient; at the same time, the present invention adopts a multi-walled carbon nanotube component with high thermal conductivity, which improves the thermal conductivity of the formulation and keeps the surface temperature T s relatively stable, reducing the dependence on the working environment temperature.

[0029] (3) On the basis of adopting copper, lead compounds and multi-walled carbon nanotubes, the present invention uses 5,5'-bistetrazole-1,1'-dioxydihydroxylammonium salt as one of the oxidants because it has a relatively high T s and endothermic gasification σ p , has a higher control of the flame temperature than AP, and the influence of the ambient temperature on its combustion decomposition degree is low; at the same time, the present invention adopts polyether binder PET and long-chain aliphatic DDI, so that the binder matrix first melts and then decomposes during combustion decomposition, keeping the surface temperature T s relatively stable, reducing the influence of the ambient temperature on combustion; through the above means, adding an energetic plasticizer to improve the specific impulse of the propellant, and reasonably grading the oxidizer particle size to further reduce the burning rate temperature sensitivity coefficient of the formulation while adjusting the burning rate, finally forming a low burning rate temperature sensitivity coefficient aluminum-free clean propellant with excellent comprehensive performance.

[0030] (4) Compared with the prior art (the burning rate temperature sensitivity coefficient is generally 0.35%K -1 , and generally contains metal powders such as aluminum powder, which is not suitable for the working environment temperature of the wide temperature range of weapon models and the stable performance requirements of engines with long-time and low-signature operation), the aluminum-free clean propellant disclosed by the present invention has the advantages of aluminum-free cleanliness in the formulation, low temperature sensitivity coefficient, high specific impulse and excellent mechanical properties, and is suitable for the application requirements of solid rocket engines with a wide temperature range of use, long range and high reliability.

[0031] (5) The aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient provided by the present invention can be used in solid rocket engines with wide temperature ranges, long times or low-signature requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic flow chart of a method for preparing an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described below through specific embodiments. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several variations and improvements can be made, which should also be regarded as belonging to the protection scope of the present invention.

[0034] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

[0035] The present invention discloses an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient, which comprises the following components by mass percentage:

[0036] Binder: 9% - 15%;

[0037] Curing agent: 0.8% - 2%;

[0038] Oxidizer: 69% - 79%;

[0039] Plasticizer: 4% - 12%

[0040] Combustion regulator: 0.5% - 2%:

[0041] Performance regulator: 0.4% - 2%.

[0042] Among them, the combustion regulator is a combination of copper and lead compounds and multi-walled carbon nanotubes. The mass percentage range of copper and lead compounds in the combustion regulator is 20% - 80%; the copper and lead compounds are a mixture of lead benzoate and copper adipate, and the mass ratio of lead benzoate to copper adipate is 1:1.

[0043] The binder is ethylene oxide-tetrahydrofuran copolymer ether (PET);

[0044] The curing agent is dimer aliphatic diisocyanate (DDI);

[0045] The oxidizer is a combination of ammonium perchlorate (AP) and 5,5'-bistetrazole-1,1'-dioxy dihydroxylammonium salt. The mass percentage range of 5,5'-bistetrazole-1,1'-dioxy dihydroxylammonium salt in the oxidizer is 2% - 30%; AP with an average particle size less than 15um is selected for compounding with 5,5'-bistetrazole-1,1'-dioxy dihydroxylammonium salt to ensure that the formulation has a low pressure index, and to realize controlling the reasonable grading of the oxidizer particle size to further reduce the burning rate temperature sensitivity coefficient of the formulation while adjusting the burning rate.

[0046] The plasticizer is one of butyl-nitroxylethyl nitramine (BuNENA), bis(2,2-dinitropropyl) formal (BDNPF), bis(2,2-dinitropropyl) acetal (BDNPA), and triethylene glycol dinitrate (TEGDN);

[0047] The performance regulator is a combination of triphenylbismuth (TPB), lecithin (Lin), tris-1-(2-methylaziridinyl) phosphine oxide (MAPO), and N-methyl-p-nitroaniline (MNA). Among them, the mass percentage range of TPB in the performance regulator is 5% - 25%, the mass percentage range of Lin in the performance regulator is 5% - 25%, the mass percentage range of MAPO in the performance regulator is 10% - 75%, and the mass percentage range of MNA in the performance regulator is 10% - 80%.

[0048] As Figure 1 shown, the present invention also discloses a preparation method of an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient, including the following steps:

[0049] S1: In a dry environment, weigh each component according to the proportion, add the combustion regulator and the performance regulator to the binder, add the plasticizer for premixing, and then add the oxidizer and control the mixing temperature at 30 - 50 °C for mixing to obtain a premixed slurry;

[0050] S2: Add the curing agent to the premixed slurry and continue to mix evenly to obtain a slurry;

[0051] S3: Vacuum pour the slurry into a mold or an engine, and place it in a dry environment at about 50 °C for curing for 7 days to obtain an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient.

[0052] Example 1

[0053] Table 1 Formulation composition of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient

[0054]

[0055] Weigh the corresponding components according to the formulation composition of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient shown in Table 1 to prepare an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient; conduct tests on the theoretical specific impulse, density, burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation rate of the aluminum-free clean propellant. Among them, the test of the theoretical specific impulse refers to: Q / Gt60, Thermodynamic performance calculation of composite solid propellants, Minimum free energy method and program; the test of density refers to: QJ917, Method for measuring the density of composite solid propellants and liners, insulation materials; the tests of burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation rate refer to: GJB770, Test methods for propellants; the test results are shown in Table 2.

[0056] Table 2 Performance of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient

[0057]

[0058] Example 2

[0059] Table 3 Formulation Composition of Aluminum-Free Clean Propellant with Low Burning Rate and Temperature Sensitivity Coefficient

[0060]

[0061] Weigh the corresponding components according to the formulation composition of the aluminum-free clean propellant with low burning rate and temperature sensitivity coefficient shown in Table 3 to prepare the aluminum-free clean propellant with low burning rate and temperature sensitivity coefficient; conduct tests on the theoretical specific impulse, density, burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant, and the test results are shown in Table 4.

[0062] Table 4 Properties of Aluminum-Free Clean Propellant with Low Burning Rate and Temperature Sensitivity Coefficient

[0063]

[0064] Example 3

[0065] Table 5 Formulation Composition of Aluminum-Free Clean Propellant with Low Burning Rate and Temperature Sensitivity Coefficient

[0066]

[0067] Weigh the corresponding components according to the formulation composition of the aluminum-free clean propellant with low burning rate and temperature sensitivity coefficient shown in Table 5 to prepare the aluminum-free clean propellant with low burning rate and temperature sensitivity coefficient; conduct tests on the theoretical specific impulse, density, burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant, and the test results are shown in Table 6.

[0068] Table 6 Properties of Aluminum-Free Clean Propellant with Low Burning Rate and Temperature Sensitivity Coefficient

[0069]

[0070] Example 4

[0071] Table 7 Formulation Composition of Aluminum-Free Clean Propellant with Low Burning Rate and Temperature Sensitivity Coefficient

[0072]

[0073]

[0074] Weigh the corresponding components according to the formulation composition of the aluminum-free clean propellant with low burning rate and temperature sensitivity coefficient shown in Table 7 to prepare the aluminum-free clean propellant with low burning rate and temperature sensitivity coefficient; conduct tests on the theoretical specific impulse, density, burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant, and the test results are shown in Table 8.

[0075] Table 8 Properties of Aluminum-Free Clean Propellant with Low Burning Rate and Temperature Sensitivity Coefficient

[0076]

[0077] Example 5

[0078] Table 9 Formulation Composition of Low Burning Rate Temperature-Sensitive Coefficient Aluminum-Free Clean Propellant

[0079]

[0080] Weigh the corresponding components according to the formulation composition of the low burning rate temperature-sensitive coefficient aluminum-free clean propellant shown in Table 9 to prepare the aluminum-free clean propellant with a low burning rate temperature-sensitive coefficient; conduct tests on the theoretical specific impulse, density, burning rate, burning rate temperature-sensitive coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant, and the test results are shown in Table 10.

[0081] Table 10 Properties of Low Burning Rate Temperature-Sensitive Coefficient Aluminum-Free Clean Propellant

[0082]

[0083]

[0084] Example 6

[0085] Table 11 Formulation Composition of Low Burning Rate Temperature-Sensitive Coefficient Aluminum-Free Clean Propellant

[0086]

[0087] Weigh the corresponding components according to the formulation composition of the low burning rate temperature-sensitive coefficient aluminum-free clean propellant shown in Table 11 to prepare the aluminum-free clean propellant with a low burning rate temperature-sensitive coefficient; conduct tests on the theoretical specific impulse, density, burning rate, burning rate temperature-sensitive coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant, and the test results are shown in Table 12.

[0088] Table 12 Properties of Low Burning Rate Temperature-Sensitive Coefficient Aluminum-Free Clean Propellant

[0089]

[0090] Example 7

[0091] Table 13 Formulation Composition of Low Burning Rate Temperature-Sensitive Coefficient Aluminum-Free Clean Propellant

[0092]

[0093]

[0094] Weigh the corresponding components according to the formulation composition of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient shown in Table 13 to prepare the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient. Test the theoretical specific impulse, density, burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant. The test results are shown in Table 14.

[0095] Table 14 Performance of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient

[0096]

[0097] Example 8

[0098] Table 15 Formulation composition of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient

[0099]

[0100] Weigh the corresponding components according to the formulation composition of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient shown in Table 15 to prepare the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient. Test the theoretical specific impulse, density, burning rate, burning rate temperature sensitivity coefficient, maximum tensile strength, and maximum elongation of this aluminum-free clean propellant. The test results are shown in Table 16.

[0101] Table 16 Performance of the aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient

[0102]

[0103] The present invention has been described in detail above in combination with specific embodiments and exemplary examples. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments; the above description should not be construed as a limitation of the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention; the protection scope of the present invention is subject to the appended claims.

Claims

1. A clean aluminum-free propellant with a low burning rate temperature sensitivity coefficient, characterized in that: The components include the following by mass percentage: Adhesive: 9% to 15%; Curing agent: 0.8%~2%; Oxidant: 69%~79%; Plasticizer: 4%~12% Combustion regulator: 0.5%~2%: Performance regulator: 0.4% to 2%; Wherein, the combustion regulator is a combination of copper, lead compounds and multi-walled carbon nanotubes; the copper, lead compounds are a mixture of lead benzoate and copper adipate, and the mass ratio of lead benzoate to copper adipate is 1:1; The performance regulator is a combination of triphenyl bismuth, lecithin, tri-1-(2-methylaziridine)phosphine oxide and N-methyl-p-nitroaniline.

2. The aluminum-free clean propellant according to claim 1, characterized in that: The mass percentage of the copper and lead compounds in the combustion regulator is in the range of 20% to 80%.

3. The aluminum-free clean propellant according to claim 1, characterized in that: The adhesive is ethylene oxide-tetrahydrofuran copolyether.

4. The aluminum-free clean propellant according to claim 1, characterized in that: The curing agent is dimer fatty acid diisocyanate.

5. The aluminum-free clean propellant according to claim 1, characterized in that: The oxidant is a combination of ammonium perchlorate and 5,5'-bistetrazolyl-1,1'-dioxadihydroxyammonium salt.

6. The aluminum-free clean propellant according to claim 5, characterized in that: The average particle size of the ammonium perchlorate and 5,5'-bistetrazolyl-1,1'-dioxadihydroxyammonium salt is less than 15 um.

7. The aluminum-free clean propellant according to claim 1, characterized in that: The plasticizer is one of butyl-nitroxyethyl nitramine, bis(2,2-dinitropropyl) formal, bis(2,2-dinitropropyl) acetal and nitrated triethylene glycol.

8. A method for preparing an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient, characterized in that: The following steps are involved: S1: Weigh each component according to the mass percentage of each component in the aluminum-free clean propellant according to any one of claims 1 to 7, add the combustion regulator and the performance regulator to the adhesive, add the plasticizer to premix, and then add the oxidant to mix to obtain a premixed slurry; S2: adding a curing agent to the premixed slurry and continuing to mix evenly to obtain a slurry; S3: Vacuum pouring the slurry into a mold or an engine, and obtaining an aluminum-free clean propellant with a low burning rate temperature sensitivity coefficient after solidification.

Images