A grading method for evaluating the influence of additives on thermal stability of explosives based on DSC

Abstract

The application discloses a grading method for evaluating the influence of additives on the thermal stability of explosives based on DSC, and belongs to the field of energetic materials and explosives. The thermal decomposition of single-element explosives and explosives with additives is tested under dynamic conditions by using DSC to obtain the number of exothermic peaks, the peak temperature of the exothermic peaks and the specific heat of unit explosives. The influence of the additives on the thermal stability of the explosives is preliminarily judged according to the number of exothermic peaks and the peak shape. If the number of exothermic peaks and the peak shape have no obvious influence, the grading evaluation is carried out according to the peak temperature of the exothermic peaks and the specific heat of unit explosives. The application has the advantages of simple test conditions, less sampling, short time consumption, low test cost, and the like. The test is carried out by using the proportion of additives and single-element explosives in an actual explosive formula, the influence of a small amount of additives on the thermal stability of single-element explosives can be accurately reflected, and more accurate results can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials and explosives, specifically relating to a classification method based on DSC to evaluate the effect of additives on the thermal stability of explosives. Background Technology

[0002] Safety is the paramount concern in the field of explosives. Thermal stability is a key indicator of the safety and reliability of explosives during production, storage, and use. Thermal stability analysis of explosives typically employs methods such as DSC, TG, and ARC to study the thermal decomposition parameters under heat, calculate reaction kinetics, and determine the optimal conditions for the development, production, and storage of explosives, ensuring their safety and reliability during production and engineering blasting.

[0003] To obtain high-performance energetic materials, explosives are now typically composite materials prepared through a series of complex processes, consisting of single or multiple elemental explosive crystals, binders, and various additives. However, the complexity of explosive formulations, especially the significant differences in thermophysical properties between explosive crystals and binders, makes the thermal behavior of composite explosives highly complex. In the DSC method for assessing the thermal stability of explosives in GJB772A-1997 (Test Methods for Explosives), additive types are usually not differentiated, and a fixed ratio of 1:1 is used to test the effect of additives on the thermal stability of elemental explosives. This amplifies the impact of materials added in small amounts in actual explosive formulations (such as binders, desensitizers, plasticizers, etc.) on the thermal stability of explosives, potentially leading to biases or even errors in the assessment of thermal stability effects. Furthermore, these evaluation methods mostly rely on single parameters, making it difficult to comprehensively reflect the effects of additives; the evaluation standards are inconsistent, and a systematic grading system is lacking.

[0004] Differential scanning calorimetry (DSC) is an important technique widely used in the thermal analysis of explosives. It offers advantages such as small sample sizes, short experimental cycles, easy control of experimental conditions, and good data reproducibility. It is also commonly used to test the thermal stability of explosives. Therefore, establishing a quantitative classification method based on DSC characteristic parameters to evaluate the impact of small amounts of added materials in actual explosive formulations on the thermal stability of explosives is of great significance. Summary of the Invention

[0005] To address the problems existing in current methods, the present invention aims to provide a classification method based on DSC (Digital Substances Computation) for evaluating the impact of additives on the thermal stability of explosives. This method involves testing based on the proportions of single-element explosives and additives in a specific explosive formulation, combined with DSC at a fixed heating rate, to obtain the number of exothermic peaks (i) and the peak temperature (T) of the exothermic peaks.P The specific heat release per unit explosive (Q') is used to preliminarily determine the effect of additives on the thermal stability of elemental explosives based on the number and shape of the exothermic peaks. If there is no significant effect on the peak shape and number, the peak temperature T of the exothermic peaks is used as the basis for judgment. P The heat release per unit of explosive, Q', is quantitatively graded and evaluated.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] A classification method for evaluating the effect of additives on the thermal stability of explosives based on DSC includes the following steps:

[0008] Step 1: Prepare single-element explosives and additives as raw materials, and mix them evenly according to the required explosive formula to obtain explosives;

[0009] Step 2: In a sealed crucible, perform dynamic thermal decomposition tests on the elemental explosive and the detonating explosive using DSC to obtain the number i and j of the exothermic peaks corresponding to the elemental explosive and the detonating explosive, i, j = 1, 2, 3...; and the peak temperature T of each exothermic peak corresponding to the elemental explosive. Pi1 The peak temperature T of each exothermic peak corresponding to the explosive is... Pj2 The specific heat release per unit explosive of the single-element explosive and the specific heat release of the pyrotechnic explosive are Q'1 and Q'2, respectively.

[0010] Step 3: Determine the changes in the exothermic process of the single-element explosive and the pyrotechnic explosive based on the number and shape of the exothermic peaks.

[0011] If there are significant changes in the number or shape of the exothermic peaks, it is considered that the thermal decomposition state of the explosive has changed, that is, the additive has a significant impact on the thermal stability of the explosive, and is classified as level 5.

[0012] If the number and shape of the exothermic peaks do not change significantly, it is considered that the thermal decomposition state of the explosive has not changed, and further quantitative classification is carried out according to step 4.

[0013] Step 4: Calculate the change in peak temperature ΔT of the exothermic peak according to formulas (1) and (2) respectively. P The rate of change of heat release per unit explosive ΔQ';

[0014] ΔT P =T Pi1 -T Pj2 (1)

[0015] Among them, T Pi1 T represents the peak temperature of the i-th exothermic peak of the single-element explosive, in °C. Pj2 Let i be the peak temperature of the j-th exothermic peak of the explosive, in °C, where i = j;

[0016] ΔQ'=|(Q'1-Q'2) / Q'1|×100% (2)

[0017] Where Q'1 is the specific heat release per unit of the single-element explosive, in J·g -1 Q'2 is the specific heat release per unit of explosive, in J·g. -1 ;

[0018] Step 5: If ΔT P If the temperature is less than 2℃ and the ΔQ' range is 0-10%, then the additive is judged to have no or little effect on the thermal stability of the explosive, and is classified as Level 1.

[0019] If ΔT P If the temperature is less than 2℃ and the ΔQ' range is 10-20%, then the additive is judged to have a small impact on the thermal stability of the explosive, which is classified as Level 2.

[0020] If ΔT P If the temperature is less than 2℃ and ΔQ' is greater than 20%, then the additive is judged to have a moderate effect on the thermal stability of the explosive, which is level 3.

[0021] If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and the ΔQ' range is 0-10%, then the additive is considered to have a small impact on the thermal stability of the explosive, and is classified as Level 2.

[0022] If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and ΔQ' is in the range of 10-20%, then the additive is judged to have a moderate effect on the thermal stability of the explosive, which is level 3.

[0023] If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and ΔQ' is greater than 20%, then the additive is judged to have a significant impact on the thermal stability of the explosive, and is classified as Level 4.

[0024] If ΔT exists P If the temperature is greater than 5℃, the additive is judged to have a significant impact on the thermal stability of the explosive, and is classified as level 5.

[0025] Furthermore, the additives include coating agents, binders, desensitizers, and plasticizers, which do not exceed 15% of the mass of the single explosive.

[0026] Furthermore, in step 3, if there are significant changes in the number or shape of the exothermic peaks, including an increase or decrease in the number of exothermic peaks, changes in peak width, or coupling or decoupling of two peaks.

[0027] Furthermore, in step 2, the sealed crucible is a high-pressure sealed stainless steel crucible, which can avoid the loss of materials or heat due to the volatilization of the product or itself, thus affecting the experimental results.

[0028] Furthermore, in step 2, the single-element explosive and the pyrotechnic explosive are subjected to dynamic thermal decomposition tests using DSC. The sample mass during the test is 0.5 mg to 1 mg, which is sufficient to ensure that the instrument does not damage the equipment and that the instrument operates safely.

[0029] Furthermore, in step 2, the single-element explosive and the pyrotechnic explosive are subjected to thermal decomposition tests under dynamic conditions using DSC. The heating rate during the test is 1-8 K / min, and all tests are repeated more than twice to eliminate instrument errors.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] This invention features simple testing conditions, requires small sampling, is time-efficient, and has low testing costs. By incorporating the influence of peak shape and number, it avoids experimental errors caused by single parameters. Using the proportions of additives and single-element explosives in actual explosive formulations for testing accurately reflects the effect of small amounts of additives on the thermal stability of single-element explosives, yielding more accurate results. This is achieved by decomposing the change in peak temperature ΔT. p The impact of the rate of change of heat release per unit explosive, ΔQ', on thermal stability is quantitatively graded, and the evaluation results are presented intuitively. Attached Figure Description

[0032] Figure 1 Dynamic DSC curves for single-element explosive CL-20 and pyrotechnic explosive CL-20 / VitonA (95:5).

[0033] Figure 2 Dynamic DSC curves for single-element explosive CL-20 and pyrotechnic explosive CL-20 / heptafluorobutyramide (95:5). Detailed Implementation

[0034] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0035] The single-component explosive in the following examples is hexanitrohexaazaisowulzane (CL-20), and the additives are fluororubber Viton A and heptafluorobutyramide.

[0036] The classification method for evaluating the effect of additives on the thermal stability of explosives based on DSC according to the present invention includes the following steps:

[0037] Step 1: Prepare the single-element explosive to be tested and additives (including coating agent, binder, desensitizer, and plasticizer, which shall not exceed 15% of the mass of the single-element explosive) as raw materials. According to the existing explosive formula, mix the raw materials evenly in proportion to obtain the explosive.

[0038] Step 2: A high-pressure sealed stainless steel crucible is used to avoid material or heat loss due to the volatilization of products or the crucible itself, which could affect the experimental results. Dynamic thermal decomposition tests are performed on the single-element explosive and the explosive under dynamic conditions using DSC. The sample mass during the test is 0.5 mg to 1 mg, ensuring that the sample mass does not damage the instrument and guarantees its safe operation. The heating rate during the test is 1-8 K / min. All tests are repeated at least twice to eliminate instrument errors. The number of exothermic peaks i and j corresponding to the single-element explosive and the explosive, i, j = 1, 2, 3..., are obtained; the peak temperature of each exothermic peak for the single-element explosive and the peak temperature T for each exothermic peak for the explosive. Pj2 The specific heat release per unit explosive of the single-element explosive and the specific heat release of the pyrotechnic explosive are Q'1 and Q'2, respectively.

[0039] Step 3: Determine the changes in the exothermic process of the single-element explosive and the pyrotechnic explosive based on the number and shape of the exothermic peaks.

[0040] If there are significant changes in the number or shape of the exothermic peaks, including an increase or decrease in the number of exothermic peaks, changes in peak width, or coupling or decoupling of double peaks, then the thermal decomposition state of the explosive is considered to have changed, i.e., the additive has a significant impact on the thermal stability of the explosive, and is classified as level 5.

[0041] If the number and shape of the exothermic peaks do not change significantly, it is considered that the thermal decomposition state of the explosive has not changed, and further quantitative classification is carried out according to step 4.

[0042] Step 4: Calculate the change in peak temperature ΔT of the exothermic peak according to formulas (1) and (2) respectively. P The rate of change of heat release per unit explosive ΔQ';

[0043] ΔT P =T Pi1 -T Pj2 (1)

[0044] Among them, T Pi1 T represents the peak temperature of the i-th exothermic peak of the single-element explosive, in °C. Pj2 Let i be the peak temperature of the j-th exothermic peak of the explosive, in °C, where i = j;

[0045] ΔQ'=|(Q'1-Q'2) / Q'1|×100% (2)

[0046] Where Q'1 is the specific heat release per unit of the single-element explosive, in J·g -1 Q'2 is the specific heat release per unit of explosive, in J·g. -1 ;

[0047] Step 5: If ΔT P If the temperature is less than 2℃ and the ΔQ' range is 0-10%, then the additive is judged to have no or little effect on the thermal stability of the explosive, and is classified as Level 1.

[0048] If ΔT P If the temperature is less than 2℃ and the ΔQ' range is 10-20%, then the additive is judged to have a small impact on the thermal stability of the explosive, which is classified as Level 2.

[0049] If ΔT P If the temperature is less than 2℃ and ΔQ' is greater than 20%, then the additive is judged to have a moderate effect on the thermal stability of the explosive, which is level 3.

[0050] If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and the ΔQ' range is 0-10%, then the additive is considered to have a small impact on the thermal stability of the explosive, and is classified as Level 2.

[0051] If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and ΔQ' is in the range of 10-20%, then the additive is judged to have a moderate effect on the thermal stability of the explosive, which is level 3.

[0052] If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and ΔQ' is greater than 20%, then the additive is judged to have a significant impact on the thermal stability of the explosive, and is classified as Level 4.

[0053] If ΔT exists P If the temperature is greater than 5℃, the additive is judged to have a significant impact on the thermal stability of the explosive, and is classified as level 5.

[0054] The classification scheme for the effect of additives on the thermal stability of explosives is shown in Table 1.

[0055] Table 1. Grading scheme for the effect of small amounts of additives on the thermal stability of explosives.

[0056]

[0057] Example 1

[0058] Step 1: Prepare the single-element explosive CL-20 and the additive VitonA. Mix CL-20 and VitonA evenly at a mass ratio of 95:5 and grind them thoroughly to obtain the explosive CL-20 / VitonA.

[0059] Step 2: Under a high-purity nitrogen atmosphere, using a high-pressure sealed stainless steel crucible, conduct thermal decomposition tests on the CL-20 / VitonA explosive using DSC under dynamic conditions (4K / min). Figure 1 As shown.

[0060] Step 3: From Figure 1 It can be seen that the addition of 5% VitonA did not significantly change the shape and number of the exothermic peaks in CL-20, suggesting that the thermal decomposition state of CL-20 / VitonA remained unchanged and further quantitative classification is needed.

[0061] Step 4: Integrate the exothermic curves of the single-element explosives CL-20 and CL-20 / VitonA to obtain the corresponding specific heat release Q, and mark the peak temperature T of the exothermic peak. p The results are shown in Table 2.

[0062] Table 2 Dynamic DSC results of single-element explosives and pyrotechnic explosives

[0063]

[0064] Calculate the change in decomposition peak temperature ΔT after adding 5% Viton A. P The rate of change of heat release per unit explosive ΔQ':

[0065] ΔT P =|244.99-246.51| = 1.52℃

[0066] ΔQ'=|(3822-4299) / 3822|×100%=12.48%

[0067] ΔT P <2℃, 10% < ΔQ' < 20%, according to Table 1, the effect of Viton A on the thermal stability of CL-20 is classified as level 2, indicating that the addition of a small amount of Viton A to the single-element explosive CL-20 has a small effect on the thermal stability of the explosive CL-20 / Viton A.

[0068] Example 2

[0069] Step 1: Prepare the single-element explosive CL-20 to be tested and the additive heptafluorobutyramide. Mix CL-20 and heptafluorobutyramide evenly and grind them thoroughly at a mass ratio of 95:5 to obtain CL-20 / heptafluorobutyramide.

[0070] Step 2: Under a high-purity nitrogen atmosphere, using a high-pressure sealed stainless steel crucible, perform thermal decomposition tests on CL-20 / heptafluorobutyramide using DSC under dynamic conditions (4K / min). Figure 2 As shown.

[0071] Step 3: From Figure 2 It can be seen that the addition of 5% heptafluorobutyramide causes a sudden jump in the exothermic peak of CL-20 and changes the peak shape. Therefore, the addition of a small amount of heptafluorobutyramide to the single explosive CL-20 has a significant impact on the thermal stability of the explosive CL-20 / heptafluorobutyramide, which is rated as level 5.

Claims

1. A classification method based on DSC to evaluate the effect of additives on the thermal stability of explosives, characterized in that, Includes the following steps: Step 1: Prepare single-element explosives and additives as raw materials, and mix them evenly according to the required explosive formula to obtain explosives; Step 2: In a sealed crucible, perform dynamic thermal decomposition tests on the elemental explosive and the pyrotechnic explosive using DSC to obtain the number i and j of the exothermic peaks corresponding to the elemental explosive and the pyrotechnic explosive, i, j = 1, 2, 3...; and the peak temperature T of each exothermic peak corresponding to the elemental explosive. Pi1 The peak temperature T of each exothermic peak corresponding to the explosive is... Pj2 The specific heat release per unit explosive of the single-element explosive and the specific heat release of the pyrotechnic explosive are Q'1 and Q'2, respectively. Step 3: Determine the changes in the exothermic process of the single-element explosive and the pyrotechnic explosive based on the number and shape of the exothermic peaks. If there are significant changes in the number or shape of the exothermic peaks, it is considered that the thermal decomposition state of the explosive has changed, that is, the additive has a significant impact on the thermal stability of the explosive, and is classified as level 5. If the number and shape of the exothermic peaks do not change significantly, it is considered that the thermal decomposition state of the explosive has not changed, and quantitative classification is carried out according to step 4. Step 4: Calculate the change in peak temperature ΔT of the exothermic peak according to formulas (1) and (2) respectively. P The rate of change of heat release per unit explosive ΔQ'; ΔT P =T Pi1 -T Pj2 (1) Among them, T Pi1 T represents the peak temperature of the i-th exothermic peak of the single-element explosive, in °C. Pj2 Let i be the peak temperature of the j-th exothermic peak of the explosive, in °C, where i = j; ΔQ'=|(Q'1-Q'2) / Q'1|×100%(2) Where Q'1 is the specific heat release per unit of the single-element explosive, in J·g -1 Q'2 is the specific heat release per unit of explosive, in J·g. -1 ; Step 5: If ΔT P If the temperature is less than 2℃ and the ΔQ' range is 0-10%, then the additive is judged to have no or little effect on the thermal stability of the explosive, and is classified as Level 1. If ΔT P If the temperature is less than 2℃ and the ΔQ' range is 10-20%, then the additive is judged to have a small impact on the thermal stability of the explosive, which is classified as Level 2. If ΔT P If the temperature is less than 2℃ and ΔQ' is greater than 20%, then the additive is judged to have a moderate effect on the thermal stability of the explosive, which is level 3. If ΔT exists P If the temperature is greater than 2℃ but less than 5℃ and ΔQ' is in the range of 0-10%, then the additive is judged to have a small impact on the thermal stability of the explosive, which is classified as Level 2. If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and ΔQ' is in the range of 10-20%, then the additive is judged to have a moderate effect on the thermal stability of the explosive, which is level 3. If ΔT exists P If the temperature is greater than 2℃ but less than 5℃, and ΔQ' is greater than 20%, then the additive is judged to have a significant impact on the thermal stability of the explosive, and is classified as Level 4. If ΔT exists P If the temperature is greater than 5℃, the additive is judged to have a significant impact on the thermal stability of the explosive, and is classified as level 5.

2. The method as described in claim 1, characterized in that, The additives include coating agents, binders, desensitizers, and plasticizers, which do not exceed 15% of the mass of the single explosive.

3. The method as described in claim 1, characterized in that, In step 3, if there are significant changes in the number or shape of the exothermic peaks, including an increase or decrease in the number of exothermic peaks, changes in peak width, or coupling or decoupling of two peaks.

4. The method as described in claim 1, characterized in that, In step 2, the sealed crucible is a high-pressure sealed stainless steel crucible.

5. The method as described in claim 1, characterized in that, In step 2, the single-element explosive and the pyrotechnic explosive are subjected to dynamic thermal decomposition tests using DSC, with the sample mass ranging from 0.5 mg to 1 mg during the test.

6. The method as described in claim 1, characterized in that, In step 2, the single-element explosive and the pyrotechnic explosive are subjected to dynamic thermal decomposition tests using DSC. The heating rate during the test is 1-8 K / min, and all tests are repeated at least twice.

Images