Shelf Life Prediction of Picric Acid via Model-Based Kinetic Analysis of Its Thermal Decomposition

A priori knowledge of the shelf life of energetic materials (EMs) is relevant due to its direct association with safety and functionality. This paper proposes a quick and reliable approach to predicting the shelf life of EMs whose thermal decomposition is an autocatalytic process once their failure threshold has been defined as a function of the limiting extent of conversion. This approach is based on the assumption of a kinetic law consistent with the autocatalytic behavior and on the subsequent extraction, via a suitable procedure of parameter identification, of the kinetics of thermal decomposition from differential scanning calorimetry (DSC) data gathered under dynamic conditions at three different heating rates. Its reliability is proven for picric acid (PA) through the comparison of kinetic predictions with evaluations of conversion obtained by using high performance liquid chromatography (HPLC) analysis for samples subjected to isothermal and non-isothermal accelerated aging tests, as well as for a sample of naturally aged material, i.e., PA, stored at room temperature for more than 10 years

Theoretical evaluation of the explosion regimes of hybrid mixtures

In a previous paper we showed that the theoretical evaluation of the thermo-kinetic parameters relevant to dust explosion (deflagration index; burning velocity and maximum pressure), may be performed by means of detailed simulations of the flame propagation of the volatiles produced during the pyrolysis/devolatilization step of the dust combustion. We recently measured the deflagration index and the maximum pressure of hybrid mixtures (nicotinic acid and methane), identifying different explosion regimes as function of the dust and gas concentrations in air. In this paper we present theoretical evaluation of the deflagration index, the burning velocity and maximum pressure for dust/gas-air mixtures at changing the concentration in order to identify the explosion regimes, experimentally found

The Combined Effect of Ambient Conditions and Diluting Salt on the Degradation of Picric Acid: An In Situ DRIFT Study

An unexpected promoting effect of KBr, used as a diluting salt, on the degradation of picric acid (PA) was observed during in situ diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments performed here under accelerated ageing conditions—at 80 °C and under an inert or oxidative atmosphere. While the formation of potassium picrate was excluded, this promoting effect—which is undesired as it masks the possible effects of test conditions on the ageing process of the material—was assumed to favor a first step of the decomposition mechanism of PA, which involves the inter- or intramolecular transfer of hydrogen to the nitro group, and possibly proceeds up to the formation of an amino group. An alternative diluting salt, ZnSe, which is much less commonly used in infrared spectroscopy than KBr, was then proposed in order to avoid misleading interpretation of the results. ZnSe was found to act as a truly inert diluting salt, preventing the promoting effect of KBr. The much more chemically inert nature (towards PA) of ZnSe compared to KBr was also confirmed, at much higher temperatures than DRIFT experiments, by dynamic differential scanning calorimetry (DSC) runs carried out on pure PA (i.e., PA without salt) and PA/salt (ZnSe or KBr) solid mixtures