Abstract

In this work chemical changes in 42 years old single base propellant induced by natural aging were evaluated. The sample was stored for a long time under uncontrolled conditions. The chemical stability was tested using High performance liquid chromatography (HPLC), High-performance thin-layer chromatography (HPTLC), the vacuum stability test (VST), SEM/EDX and visual analysis by Stereo Microscope. Heat flow calorimetry (HFC) method was used for analysis of thermal behavior of the sample. Visual changes in appearance of the 42 years old propellant sample surface were apparent. HPLC analysis showed that the sample contains very low effective stabilizer content (<0.2%) and VST measured very high gas release (ΔVST gas >2 ml/g). Therefore, the propellant is classified as very unstable. Although the effective stabilizer is almost completely consumed, the sample demonstrated very good thermal properties measured using HFC where the heat flow limit of 114 μW/g was not exceeded. The presence of inorganic stabilizers which could contribute to stability was examined using SEM/EDX. The results showed only presence of C, O and N and traces of Si. It could be assumed that even though all the parent DPA is almost consumed, the remaining daughter stabilizer products continue to protect the propellant from possible self-ignition for a long period of time.

Key words: Propellants, natural aging, chemical stability.