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

Abstract

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.

Principal Component Analysis of FTIR Data to Accurately Assess the Real/Equivalent In‐Service‐Times of Homogenous Solid Propellant

“…Principal component analysis, which is probably the most used multivariate analysis, aims to reduce the amount of the data for which the variables could be correlated [11]. Only those presenting the most important pieces of information are valorized [12]. More explicitly, the PCA method is used to extract the systematic variance in the data matrix [13].…”

Towards a Deep Insight Into Thermal and Moisture Aging of Silicon‐Based Pyrotechnic Delay Composition Through a Combination of Spectroscopic Techniques – Principal Component Analysis Approaches

“…Therefore, scientists employed accelerated aging techniques [13][14][15][16][17], which enable us to observe the effect of an experimental (non-natural) stress over a short time frame with which one can estimate the lifetime of the aged samples [18][19][20][21]. Several works published so far aimed at understanding the aging of pyrotechnic compositions [8,17,[22][23][24] under various aging conditions, i. e., temperature and humidity. Despite that, only a few of them have studied the aging of pyrotechnic delay compositions [8,10,16,25,26].…”

“…However, several studies followed quite interesting approaches consisting of the use of non-calorimetric methods or spectroscopic techniques such as XRD, Raman, photoelectron spectroscopy, etc. to investigate the aging of such pyrotechnic compositions [22,23,25]. It was revealed that non-calorimetric approaches are highly suitable to study the compositional changes induced by such relevant aging processes within the studied pyrotechnics [22,23,25].…”

“…to investigate the aging of such pyrotechnic compositions [22,23,25]. It was revealed that non-calorimetric approaches are highly suitable to study the compositional changes induced by such relevant aging processes within the studied pyrotechnics [22,23,25].…”

“…PCA is a classification method that facilitates samples grouping by maximizing the variance of the studied categories [42]. This method has been already coupled with spectroscopic methods and applied by our research group for the study of single-based, double-base propellants, and pyrotechnic compositions [19,22,23], and it demonstrated its efficiency to assess the aging process of such kind of energetic materials.…”