Where :k is the initial reaction velocity constant (1s) at a certain temperature; A refers to the pre-factor; T is the temperature; R is the universal gas constant (11kJKmol); E is the activation energy of the decomposition reaction (1kJmol).

The formula (1-2) is obtained by dividing (1-1)

1.2 Research methods of explosive thermal decomposition 

Thermal Gravimetry (TG) is a method to determine the mass of substances as they change with temperature. It was first published in 1915 by Kotaro Honda of the University of Tokyo, Japan, who designed the first simple thermal balance. Due to the long measurement time and the limited stability of the instrument, the thermal balance has not been widely used. Then with the continuous improvement of thermal analysis technology. The above methods can only directly or indirectly measure the total amount of released gas and volatilization, as well as study the phenomenological reaction kinetics, but can not qualitatively and quantitatively measure the components and content in the gas, nor can they clarify the mechanism of the reaction. The Chemical Reactivity Test (CRT) developed on the basis of gas chromatography was first used to replace the vacuum stability test method in the Pantex factory in the United States in the early 1960s. This method can not only accurately determine the total amount of released gas, but also quickly determine the content of NO2,CO2, H2O,CO,NO and other components. 

The chemiluminescence method developed in the early 1970s is mainly used to determine the content of NOx generated by the thermal decomposition reaction of explosives at lower temperatures, and its sensitivity can reach ppb level. It is of great significance for measuring the thermal stability and compatibility of explosives at storage temperature and predicting the storage life.  

Temperature Modulation is introduced into thermal analysis, resulting in thermal analysis techniques such as MDSC and TMTG. They also play an important role in the thermal analysis process. In addition, the quasi-definite and quasi-isobaric TA techniques developed by Paulik et al. are promising thermal analysis methods.

The Accelerating Rate Calorimetry (ARC) test developed in recent years is a new method to evaluate the risk of exothermic chemical substances. The method is described in 2.1. Accelerated calorimeter is a new thermal analysis instrument recommended by the United Nations for the assessment of dangerous goods. The thermodynamic and kinetic information of exothermic reaction can be obtained by ARC test. The accelerated calorimeter can ensure that the sample in the test environment is completely adiabatic condition to measure the change of time, temperature and pressure during the sample thermal decomposition reaction. Various kinetic parameters of exothermic reaction can be determined by establishing mathematical model. According to these parameters, the risk of the reaction object can be accurately predicted. Compared with DSC and other methods, it has incomparable advantages, especially it can give the slow change process of pressure in the early stage of thermal decomposition of substances that can not be given by DTA and DSC. 

Accelerated calorimeter is a calorimeter designed on the basis of adiabatic principle. It can provide time-temperature-pressure data of chemical reaction under adiabatic conditions with a large sample size and high sensitivity. It can accurately measure the initial temperature of sample thermal decomposition and the curve of temperature and pressure change with time during adiabatic decomposition. Various thermodynamic and kinetic parameters of exothermic reaction can be determined. According to these parameters, the risk of the reaction object can be accurately predicted.

The acceleration calorimeter is started by setting the initial temperature, slope sensitivity, heating amplitude, termination temperature and waiting time on the ARC controller. The acceleration calorimeter quickly raises the temperature to the starting temperature and then automatically operates in a "heat-wait-search" manner (see Figure 2.1). In the "heating" stage, the temperature of the acceleration calorimeter rises according to the set heating range; In the "waiting" stage, the accelerated calorimeter establishes the temperature balance in the adiabatic furnace. ARC enters the "search" phase, comparing the temperature rise rate of the sample with the set slope sensitivity, if the former is less than the latter, it automatically enters the next "heat-wait-search" cycle; If the former is greater than the latter, the accelerated calorimeter automatically switches to the "exothermic" mode and records information such as temperature, pressure and temperature rise rate during the entire reaction process. 

2.3 Structure of acceleration calorimeter 

Where mt, dT/dt is the temperature rise rate of the reactant at temperature T; ΔTab is the adiabatic temperature rise of the reactant, ΔTab=Tf-To, where the sign is the temperature at the end of the reaction, and To is the initial heat release temperature of the inverse; f(a) is the reaction mechanism function, where

 The kinetic data such as apparent activation energy Ea, pre-exponential factor A and reaction order can be obtained by ARC system calculation. However, the equation (*) is based on the ideal case that the heat released by the chemical reaction is used only to heat the specimen itself, without taking into account the presence of the reaction vessel. In fact, whether in practical applications or in ARC tests, part of the heat released by the reaction is used to heat the reaction vessel. Therefore, it needs to be amended. Correction factor introduced into the sample container:

3. Test results and analysis of accelerated calorimeter 

ARC test results of emulsion explosive are shown in FIG. 3.1.