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

This study was devoted to setting up new methodologies for an accurate assessment of both real and equivalent in-service-times (RIST/EIST) of homogenous solid propellants (HSP) through a combination of principal component analysis (PCA) and Fourier transform infrared (FTIR) spectroscopy. Four double-base rocket propellants (DBRP) have been artificially aged at T=338.65 K for 4 months with sampling every 20 days. FTIR showed that the homolytic scission of the O-NO2 bonds and the hydrocarbon chains of the nitrate esters are the main processes occurring during the chemical decomposition. The scatter plot from PCA of FTIR spectra shows that over 93 % of the variance was described by the first principal component. Moreover, the loading plot designated the three characteristic FTIR bands from the nitro (NO2) group as the most influenced by aging. A new PCA/FTIR experimental way was set to accurately assess the RIST of HSPs. The relative deviation associated with the RIST evaluated by the present procedure and those from the PCA/VST experimental way, recently developed, was found to range from 4.0 % to 6.7 %. Subsequently, a PCA/FTIR prediction model of the EIST is established. The predictions present a relative deviation of less than 7.1 % compared to the recent PCA/VST model. The accuracy of the model was further confirmed using similar DBRPs artificially aged for 6, 8, 10, and 12 months. The relative variation between the RIST provided by the PCA/FTIR procedure and the prediction model was found less than 5 %, thus confirming the highest accuracy of such combination.

Automated summary

This study established a new method for accurately assessing the real and equivalent in-service times of homogenous solid propellants through the combination of PCA and FTIR spectroscopy. Experimental verification on four double-base rocket propellants confirmed the accuracy of the method.