Towards understanding the effect of humidity on the degradation of pyrotechnic compositions through spectroscopic data combined with chemometric methods

In the current study, two pyrotechnic compositions (tracer and igniter) containing magnesium and phenolic resin have been subjected to moisture-induced aging at 85 % relative humidity to gain better understanding of environmental needs for their long-storage. Non-destructive analytical methods have been explored to investigate the effect of aging at a prolonged duration on pyrotechnics properties and their thermal behavior. The degradation of these pyrotechnic compositions during aging has been assessed using X-ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopies, and scanning electron microscopy. It is revealed that some physical changes such as the appearance of micro-cracks on the particle surfaces and chemical modifications such as the formation of magnesium hydroxide and nitrite-based compounds occurred during aging. These changes affect the thermal stability of these pyrotechnic compositions as found by thermogravimetric analyses, which may increase the risk of a misfire. Moreover, the FTIR and Raman spectroscopic data were coupled with two different qualitative multivariate analysis techniques, i. e., hierarchical cluster analysis (HCA) and principal component analysis (PCA) for the classification and discrimination of the spectra of the aged specimens. The obtained results demonstrated the efficiency of the adopted methodologies to easily elucidate the structural and compositional modifications that may happen within the pyrotechnic compositions during moisture-induced aging.