Comparing thermal and chemical analysis of aged and unaged NC-based propellants

Abstract. Authors: R.J.O. de Vries, E.L.M. la Haye Nitrocellulose (NC)-based propellants gradually decompose during ageing. Stabilizers are used to mitigate NC degradation, ensuring safer storage and performance. Traditionally thermal analysis techniques such as Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Pressure Vacuum Stability Testing (PVST), along with accelerated ageing studies using Heat Flow Calorimetry (HFC), have been used to evaluate the stability and predict the lifetime of propellants. While these methods provide valuable insights, they are often limited in their ability to detect localized variations in composition within propellant samples. This study investigated the stability of two double-base NC-based propellants subjected to ageing under two distinct temperature conditions: a hot environment and a cold environment. Samples were analyzed at different locations within the propellant: top edge, middle, bottom and inhibitor layers (top and bottom), to evaluate spatial variations within the sample. Analytical methods included HFC, DSC, PVST, and Ultra High Performance Liquid Chromatography (UPLC). While HFC and DSC results showed no significant differences between aged and unaged samples, PVST and UPLC analyses revealed local variations in nitroglycerin (NG) and stabilizer content. UPLC detected a decrease in NG levels, particularly from the middle to the bottom section of the propellant. Furthermore, stabilizer content measurements confirmed expected reductions with ageing. These findings highlight the complementarity of UPLC in detecting localized chemical changes due to ageing, which thermal analysis techniques may not reveal. This study highlights the importance of combining multiple analytical techniques to assess the ageing behavior of NC-based propellants. By using UPLC, the identification of localized variations in the composition of a gun propellant due to ageing, which might not be revealed with thermal analysis alone, might be crucial for improving the predictive accuracy of propellant stability and ensuring their safe and reliable use.