A rapid assessment method for thermal safety of small-charge explosives based on adiabatic acceleration calorimetry

Abstract

The present invention discloses a method for rapid thermal safety assessment of small-charge explosives based on adiabatic acceleration calorimetry, which relates to the field of energetic material analysis technology and safety assessment. The method of the present invention analyzes the evolution law of temperature-pressure-time during adiabatic decomposition of elemental or formulated explosives through adiabatic acceleration calorimetry of explosives, and extracts key pressure parameters of adiabatic decomposition; utilizes the distribution of pressure parameters and temperature to achieve a preliminary classification of the thermal safety hazard level of elemental explosives; and combines the slow-burning reaction level of formulated explosives to achieve rapid assessment and quantitative evaluation of the thermal safety of small-charge explosives during slow-burning. The method of the present invention uses explosives in the order of only hundreds of milligrams, is low in cost, safe and reliable, is conducive to the study of the laws of thermal safety of explosives and the development of new explosives, and has considerable application prospects in the field of energetic materials.

Description

Technical Field

[0001] The invention belongs to the field of energetic material analysis technology and safety assessment, and in particular relates to a method for rapid thermal safety assessment of small-amount explosives based on adiabatic acceleration calorimetry. Background Art

[0002] Explosives are often exposed to thermal stress during production, storage, and use, such as slow temperature rise caused by poor heat dissipation in storage environments and direct flame heating from accidental fires. Under these thermal conditions, explosives can undergo decomposition, combustion, or even explosion, resulting in serious safety incidents. Therefore, research on the thermal safety of explosives is of great practical significance and has attracted widespread attention among researchers in the field of energetic materials.

[0003] Cook-off tests are the primary means of evaluating the thermal safety of explosive specimens or ammunition. These tests are categorized into slow and fast cook-offs. Slow cook-offs pose a more serious threat to explosive thermal safety and are highly valued by major military powers (Research Progress on Thermal Safety of Energetic Materials, Equipment Environmental Engineering, 2022, 19, 1-10). Military standards (MIL-STD-2015D, STANG4382) have been established by the United States, the United Kingdom, and NATO, specifying test conditions for slow cook-offs, such as a heating rate of 3.3°C / h. Slow cook-offs can measure key parameters such as the cook-off response time, response temperature, and response overpressure. Combined with the degree of damage to the test apparatus, these responses are qualitatively classified into five levels: detonation, partial detonation, explosion, deflagration, and combustion (A Review of Cook-off Test Technology for Insensitive Ammunition, Journal of Detection and Control, 2019, 41, 1-9). For slow cook-off tests, Chinese patents CN106588520B, CN109184954B, CN107085011B, CN104949587A, CN107102025A, and CN114813834A have respectively investigated energetic formulations, experimental apparatus, heating rates, and numerical simulations. However, slow cook-offs require large amounts of explosives (over 20g), pose significant risks, and are expensive to conduct. This makes it difficult to quantitatively characterize the thermal safety of explosives. This hinders the study of thermal safety variations and the development of new explosives due to difficulties in obtaining sufficient sample quantities.

[0004] The thermal decomposition characteristics of explosive powders can be studied using methods such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and adiabatic acceleration calorimetry (ARC) (Research Progress on Thermal Stability and Thermal Safety Evaluation Methods of Energetic Materials, Chemical Propellants and Polymer Materials, 2004, 2, 22-24). DSC and TGA methods use very small amounts of explosive (less than 5 mg), making them difficult to characterize, and their thermal decomposition characteristics are related to the heating rate. The ARC method, however, uses hundreds of milligrams of explosive, providing better representation and capturing the decomposition characteristics of explosives under adiabatic conditions. Chinese patent CN112033998A uses the ARC method to calculate the temperature corresponding to the time at which the maximum reaction rate of explosives is reached under adiabatic conditions and compares it with the process temperature, thus proposing a thermal stability classification method for explosive materials. Currently, the thermal safety (or thermal stability) of explosive powders primarily focuses on changes in the pyrolysis temperature. Few studies have examined the variation of the thermal decomposition pressure parameter of explosives. However, the pressure generated by explosive decomposition, combustion, or explosion can cause varying degrees of damage to the test equipment during cook-off tests, thereby affecting the thermal safety of the burn-off. Furthermore, there is a lack of effective communication between the thermal decomposition characteristics of explosives and their thermal safety, and a lack of methods for assessing the thermal safety of small explosive doses. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a rapid thermal safety assessment method for small-charge explosives based on adiabatic acceleration calorimetry. The core of the invention lies in analyzing the temperature-pressure-time evolution during the adiabatic decomposition of elemental or formulated explosives to extract the key pressure parameters for adiabatic decomposition. The pressure parameter and temperature distribution are then used to perform a preliminary classification of the thermal safety hazard level of elemental explosives. Furthermore, a rapid thermal safety assessment method for slow cook-off of small-charge explosives is established, combining the slow cook-off reaction level of formulated explosives.

[0006] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0007] A method for rapid thermal safety assessment of small-charge explosives based on adiabatic acceleration calorimetry comprises the following steps:

[0008] (1) placing the elemental explosive powder or the formulated explosive powder in the sample cell of an adiabatic accelerating calorimeter, setting a temperature program, performing adiabatic decomposition of the explosive, and obtaining and recording the adiabatic decomposition curve;

[0009] (2) Analyze the evolution of adiabatic decomposition curves of different types of explosives and extract key pressure parameters;

[0010] (3) According to the distribution of key pressure parameters and temperature, the intervals are identified and divided to achieve a preliminary classification of the thermal safety hazard level of single-element explosives; combined with the measured slow combustion reaction level of formulated explosives, the intervals are identified and divided to achieve a rapid assessment of the thermal safety of formulated explosives.

[0011] A further technical solution is that in step (1), the mass of the single explosive powder or the formulated explosive molding powder is 100-300 mg.

[0012] A further technical solution is that in step (1), the single explosive includes but is not limited to one or more of pentaerythritol tetranitrate (PETN), triaminotrinitrobenzene (TATB), cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), hexanitrohexaazaisowurtzitane (CL-20), 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), trinitrotoluene (TNT), 1,1-diamino-2,2-dinitroethylene (FOX-7), hexanitrostilbene (HNS), 1,1-diamino-4,4,5,5-tetranitro-2,2-biimidazole (DATNBI), 1,1-dihydroxy-5,5-tetrazolyl dihydroxyamine salt (TKX-50), and 3,3-diamino-4,4-azofurazan (DAAzF), and the formula explosive molding powder includes but is not limited to HMX-based molding powder and TATB-based molding powder.

[0013] A further technical solution is that in step (1), the heating program is set as follows: heating from room temperature to 80-150°C, and maintaining the temperature for 10min-5h; then, the heating program is set according to the heating-waiting-searching mode of the adiabatic accelerating calorimeter, setting the heating rate to 0.5-5.0°C / min, the step size to 0.5-20.0°C, the waiting time to 10min-4h and the end temperature to 300-500°C.

[0014] A further technical solution is that in step (2), the evolution law of the adiabatic decomposition curve includes the change law of temperature-time, temperature rise rate-temperature, temperature rise rate-time, pressure-time, pressure rise rate-temperature and pressure rise rate-time during the adiabatic decomposition of the explosive; and the key pressure parameter is selected from one or more of the starting pressure, inflection point pressure, maximum pressure, starting pressure rise rate, inflection point pressure rise rate and maximum pressure rise rate.

[0015] Preferably, the key pressure parameters are one or more of the inflection point pressure, the maximum pressure, and the maximum pressure rise rate.

[0016] A further technical solution is that in step (3), the distribution of the key pressure parameters and temperature is selected from one or more of the two-dimensional distributions of starting pressure-temperature, inflection point pressure-temperature, maximum pressure-temperature, starting pressure rise rate-temperature, inflection point pressure rise rate-temperature, maximum pressure rise rate-temperature, maximum pressure / temperature-temperature, and maximum pressure rise rate / temperature-temperature.

[0017] Preferably, the distribution of the key pressure parameters and temperature is one or more of the two-dimensional distributions of inflection point pressure-temperature, maximum pressure-temperature, maximum pressure rise rate-temperature, maximum pressure / temperature-temperature, and maximum pressure rise rate / temperature-temperature.

[0018] A further technical solution is that in step (3), the division interval is the classification of thermal safety hazard levels, which is divided into 3-4 hazard levels; the thermal safety rapid assessment refers to the rapid estimation of the slow combustion reaction level of the formulated explosive, involving one or more of the explosion, deflagration, and combustion reaction levels.

[0019] The present invention also provides the above-mentioned method for rapid thermal safety assessment of small-charge explosives based on adiabatic acceleration calorimetry, and its application in the fields of explosives, propellants, and pyrotechnic energetic materials.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The amount of explosive used in the present invention is several hundred milligrams, which is safe and reliable, has low cost, and is conducive to studying the thermal safety of new explosives.

[0022] (2) The method for rapid evaluation of thermal safety of small amounts of explosives provided by the present invention promotes the quantification of the evaluation method and helps to study the influence of explosive composition, structure and aging on thermal safety.

[0023] (3) The method for rapid assessment of thermal safety of small amounts of explosives provided by the present invention is expected to be extended to the study of thermal safety of energetic materials such as propellants and pyrotechnics. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a flow chart of the method for rapid thermal safety assessment of small-charge explosives based on adiabatic acceleration calorimetry of the present invention.

[0025] Figure 2 The adiabatic decomposition curve and analysis points of the TATB elemental explosive in Example 1 are shown.

[0026] Figure 3 This is a diagram showing the key pressure parameter-temperature distribution for the adiabatic decomposition of the elemental explosive in Example 1.

[0027] Figure 4The thermal safety hazard level classification of elemental explosives is based on the key pressure parameter-temperature distribution.

[0028] Figure 5 Graph showing the key pressure parameters, temperature distribution, and thermal safety assessment of slow cooking for the adiabatic decomposition of the explosive molding powder formulated in Example 2. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. The single-element explosives or formulated explosive molding powders used in the following embodiments were purchased from commercial channels or developed by specific units.

[0030] Example 1

[0031] In this example, 167 mg of elemental explosive was placed in a spherical sample cell of an adiabatic accelerating rate calorimeter. The sample cell was made of stainless steel or titanium and installed in the reactor of the adiabatic accelerating rate calorimeter. Adiabatic decomposition of the elemental explosive was performed to obtain an adiabatic decomposition curve. The elemental explosives used in this example included PETN, TATB, RDX, HMX, CL-20, LLM-105, TNT, FOX-7, HNS, DATNBI, TKX-50, and DAAzF, all of which were explosive powders.

[0032] The heating program of this embodiment is as follows: heating from room temperature to 100°C at 10°C / min and maintaining the temperature for 1 hour; then entering the heating-waiting-searching mode (HWS): heating rate: 2.0°C / min, step size: 3.0°C, waiting time for each step is 40 minutes, and the end temperature is 450°C.

[0033] Figure 2 The adiabatic decomposition curve and analysis points of the TATB elemental explosive obtained in this example are shown below. Figure 2 As can be seen, adiabatic accelerating rate calorimetry can simultaneously monitor the temperature-pressure-time evolution of the adiabatic decomposition of explosives. After obtaining the decomposition curve, key analysis points include the onset, inflection point, peak point (maximum temperature or maximum pressure), and the thermal runaway interval between the onset and inflection points. The decomposition curve provides corresponding parameters such as time, temperature, pressure, rate of temperature rise, and rate of pressure rise. The inductive analysis of these parameters is beneficial for understanding the thermal safety evolution of elemental explosives. Figure 3 The key pressure parameter-temperature distribution diagram of the adiabatic decomposition of the single explosive extracted in this embodiment includes three types of distribution diagrams: maximum pressure-temperature, maximum pressure rise rate-temperature and inflection point pressure-temperature. Figure 3It can be seen that in addition to the differences in pyrolysis temperature, key pressure parameters of different types of elemental explosives also show significant changes. Among them, the pyrolysis temperature of the insensitive explosive TATB and the heat-resistant explosive LLM-105 is higher (greater than 320℃), and the maximum pressure, maximum pressure rise rate and inflection point pressure generated by adiabatic decomposition are all lower ( Figure 3 ). This indicates that the gas products produced during the adiabatic decomposition of TATB and LLM-105 are relatively small and the formation pressure is relatively low. However, the pyrolysis temperature of nitramine explosives (RDX, HMX) and nitrate ester explosives (PETN) gradually decreases, and the maximum pressure, maximum pressure rise rate and inflection point pressure generated increase ( Figure 3 This indicates that the adiabatic decomposition of RDX, HMX, and PETN produces more gaseous products and generates higher pressure. Therefore, the distribution of key pressure parameters and temperature indicates that the thermal safety of TATB and LLM-105 is better than that of nitramine or nitrate ester explosives, which is consistent with the general understanding of thermal sensitivity in the field of energetic materials ( Figure 3 At the same time, the introduction of key pressure parameters enriches the evaluation indicators of explosive thermal safety, no longer focusing solely on thermal decomposition temperature. Figure 4 This is the thermal safety hazard level classification of single explosives based on the key pressure parameter-temperature distribution in this embodiment, including the maximum pressure / temperature-temperature and maximum pressure rise rate / temperature-temperature distribution situations. Figure 4 It can be seen that the distribution of the two key parameters, pressure and temperature, can both classify the thermal safety hazard levels of the 12 types of elemental explosives. Based on the distribution and the critical value of the pressure parameter, this embodiment divides the thermal safety hazard levels of the 12 types of elemental explosives into 4 categories ( Figure 4 Among them, TATB, LLM-105, and DAAzF belong to Class I, with higher pyrolysis temperatures and lower pressure parameters; HNS belongs to Class II, with higher pyrolysis temperatures and pressure parameters; TNT and DATNBI belong to Class III, with lower pyrolysis temperatures and pressure parameters; PETN, RDX, HMX, CL-20, FOX-7, and TKX-50 belong to Class IV, with lower pyrolysis temperatures and higher pressure parameters ( Figure 4 Within the same hazard level, the pressure parameter-temperature distribution of different elemental explosives also varies. In summary, the pressure parameter-temperature two-dimensional distribution assessment method based on adiabatic acceleration calorimetry provided by the present invention can achieve a preliminary classification of the thermal safety hazard level of elemental explosives.

[0034] Example 2

[0035] In this example, 167 mg of TATB- and HMX-based modeling powders were placed in a spherical sample cell of an adiabatic accelerating rate calorimeter. The sample cell was made of stainless steel or titanium and installed in the reactor of the adiabatic accelerating rate calorimeter. The modeling powders were adiabatically decomposed to obtain an adiabatic decomposition curve. The heating program used in this example was the same as in Example 1.

[0036] At the same time, the slow cook-off reaction levels of TATB and HMX based explosives were obtained through cook-off tests under the following conditions: the charge size was The heating rate is about 3°C / min until the explosive reacts and the test device is destroyed. The degree of slow burn reaction is determined by the degree of device destruction (number or size of fragments).

[0037] Figure 5 The key pressure parameter-temperature distribution of the adiabatic decomposition of TATB and HMX-based explosive molding powders and the thermal safety assessment diagram of slow cooking are shown. The maximum pressure / temperature-temperature distribution shows that there are significant differences in the key pressure parameter-temperature distribution ranges of TATB-based and HMX-based explosive molding powders ( Figure 5 a). Among them, the pyrolysis temperature of TATB-based explosive molding powder is about greater than 340℃, the maximum pressure / temperature is about less than 3.0KPa / ℃, and its slow cooking reaction level is combustion; however, the pyrolysis temperature of HMX-based explosive molding powder is about less than 260℃, the maximum pressure / temperature is about greater than 8.0KPa / ℃, and its slow cooking reaction level is explosion; after adding functional additives, the pyrolysis temperature of the modified HMX-based explosive molding powder is slightly increased, and the pressure parameters are significantly decreased, and its corresponding slow cooking reaction level is deflagration. In addition, the distribution of maximum pressure rise rate / temperature-temperature can also distinguish the slow cooking reaction levels of TATB-based and HMX-based explosives ( Figure 5 b) Therefore, the present invention can analyze the distribution of key pressure parameters such as maximum pressure / temperature-temperature through adiabatic accelerated calorimetry analysis of small-charge explosives, thereby achieving rapid assessment and quantitative evaluation of the thermal safety of formulated explosives during slow cook-off.

[0038] In summary, the present invention provides a rapid thermal safety assessment method for small explosive charges based on adiabatic acceleration calorimetry. By analyzing explosive samples using adiabatic acceleration calorimetry, the key pressure parameter-temperature distribution is analyzed. This method can provide a preliminary classification of the thermal safety hazard level of elemental explosives and a rapid and quantitative assessment of the thermal safety of formulated explosives during slow cooking. This method utilizes explosives in quantities of only hundreds of milligrams, is cost-effective, and is safe and reliable. It facilitates the study of thermal safety patterns in explosives and has considerable application prospects in the field of energetic materials.

[0039] Although the present invention is described herein with reference to illustrative embodiments of the present invention, the above embodiments are merely preferred embodiments of the present invention, and the embodiments of the present invention are not limited to the above embodiments. It should be understood that those skilled in the art can design many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A method for rapid assessment of thermal safety of small-charge explosives based on adiabatic acceleration calorimetry, characterized in that: The following steps are involved: (1) placing a single explosive powder or a formulated explosive molding powder in a sample cell of an adiabatic accelerating rate calorimeter, wherein the mass of the single explosive powder or the formulated explosive molding powder is 100-300 mg; Set the temperature rising program to perform adiabatic decomposition of explosives, obtain and record the adiabatic decomposition curve; (2) Analyze the evolution of adiabatic decomposition curves of different types of explosives and extract key pressure parameters; (3) Based on the distribution of key pressure parameters and temperature, the intervals are identified and divided to achieve a preliminary classification of the thermal safety hazard level of single-element explosives; combined with the measured slow combustion reaction level of formulated explosives, the intervals are identified and divided to achieve a rapid assessment of the thermal safety of formulated explosives.

2. The method for rapid assessment of thermal safety of small-charge explosives based on adiabatic acceleration calorimetry according to claim 1, characterized in that: In step (1), the elemental explosive comprises one or more of pentaerythritol tetranitrate, triaminotrinitrobenzene, cyclotrimethylene trinitramine, cyclotetramethylene tetranitramine, hexanitrohexaazaisowurtzitane, 2,6-diamino-3,5-dinitropyrazine-1-oxide, trinitrotoluene, 1,1-diamino-2,2-dinitroethylene, hexanitrostilbene, 1,1-diamino-4,4,5,5-tetranitro-2,2-biimidazole, 1,1-dihydroxy-5,5-tetrazolyl dihydroxyamine salt, and 3,3-diamino-4,4-azofurazan, and the formula explosive molding powder comprises HMX-based molding powder and TATB-based molding powder.

3. The method for rapid assessment of thermal safety of small-amount explosives based on adiabatic acceleration calorimetry according to claim 1, characterized in that: In step (1), the temperature rise program is set as follows: from room temperature to 80-150 o C, constant temperature for 10 min-5h; then, the heating program was set according to the heating-waiting-searching mode of the adiabatic accelerating calorimeter, and the heating rate was set to 0.5-5.0 o C / min, step length 0.5-20.0 o C. Waiting time 10 min-4 h and end temperature 300-500 o C.

4. The method for rapid assessment of thermal safety of small-amount explosives based on adiabatic acceleration calorimetry according to claim 1, characterized in that: In step (2), the evolution law of the adiabatic decomposition curve includes the variation law of temperature-time, temperature rise rate-temperature, temperature rise rate-time, pressure-time, pressure rise rate-temperature and pressure rise rate-time during the adiabatic decomposition of the explosive; and the key pressure parameter is selected from one or more of the starting pressure, inflection point pressure, maximum pressure, starting pressure rise rate, inflection point pressure rise rate and maximum pressure rise rate.

5. The method for rapid assessment of thermal safety of small-charge explosives based on adiabatic acceleration calorimetry according to claim 1, characterized in that: In step (3), the distribution of the key pressure parameters and temperature is selected from one or more of the two-dimensional distributions of starting pressure-temperature, inflection point pressure-temperature, maximum pressure-temperature, starting pressure rise rate-temperature, inflection point pressure rise rate-temperature, maximum pressure rise rate-temperature, maximum pressure / temperature-temperature, and maximum pressure rise rate / temperature-temperature.

6. The method for rapid assessment of thermal safety of small-charge explosives based on adiabatic acceleration calorimetry according to claim 1, characterized in that: In step (3), the division interval is the classification of thermal safety hazard levels, which is divided into 3-4 hazard levels; the thermal safety rapid assessment refers to the rapid estimation of the slow burn reaction level of the formulated explosive, involving one or more of the explosion, deflagration, and combustion reaction levels.

7. Application of a method for rapid assessment of thermal safety of small-charge explosives, characterized in that: The method for rapid thermal safety assessment of small-charge explosives based on adiabatic acceleration calorimetry as described in any one of claims 1 to 6 is applied in the fields of explosives, propellants, and pyrotechnic energetic materials.

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