Insight into the Effect of Moisture and Thermal Aging on the Degradation of a Pyrotechnic Igniter Composition through Thermogravimetric Kinetics Coupled with Deconvolution Approach

Abstract

In the present study, the effect of moisture and thermal aging on the degradation of a pyrotechnic igniter composition (PIC) composed of magnesium (Mg) as fuel and dual‐oxidizer of barium nitrate (Ba(NO3)2) and barium peroxide (BaO2) has been investigated to well understand the main compositional and structural changes that may occur. The unaged and aged samples were examined through non‐destructive techniques, namely, Raman and Fourier transform infrared (FTIR) spectroscopies, scanning electron microscopy (SEM), and X‐ray diffraction (XRD). The thermal decomposition behavior and the kinetic parameters of the different Mg‐PIC samples were determined using thermogravimetry (TGA) analysis coupled with a deconvolution approach. The obtained results revealed that the aging processes performed at 65 °C and 85 % relative humidity (RH), respectively, affected the chemical structure of the samples, and the degradation became more pronounced with the increase of the aging time. These changes are attributed to the partial decomposition of barium nitrate, barium peroxide, and the oxidation of magnesium, which generated Ba(NO2)2, MgO, and Mg(OH)2 as degradation products. On the other hand, based on the TGA data, the kinetic modelling was carried out through the deconvolution approach combined with isoconversional kinetic analysis to determine the multiple‐step kinetic behaviors of the different PIC samples. The results revealed that the aging processes may engender various degradation reactions with different activation energies compared to the fresh sample, what can lead to severe changes in stability and untrustworthy performance of the pyrotechnic compositions.