Development of T-jump/Raman spectroscopy as a complement to T-jump/FTIR spectroscopy for the pyrolysis of energetic materials

In the attempt to understand various combustion issues, several methods have previously been used to generate combustion-like simulations for energetic materials. Low heating rate and temperature experiments have been conducted using DSC and TGA. Information obtained was useful but could not be extrapolated into combustion processes. However controlled higher heating rate experiments using FTIR detection have provided further insight into the mechanism of decomposition by analyzing evolution of gaseous products. As only IR-active species were detected, the stoichiometry of the decomposition reaction could only partially be determined. The decomposition equation was computed by assuming that O₂, H₂, and N₂ made up the difference in the atom balance. Advances made in this dissertation, namely the development of T-jump/Raman spectroscopy, eliminated the need to assume the concentrations of IR-inactive products.; T-Jump/Raman spectroscopy, like its complement T-jump/FTIR spectroscopy, utilizes a controlled, high heating rate to pyrolyze energetic materials. The method was validated using a variety of test materials: cured mixtures of BTTN/GAP/RDX, nitrate esters, and 5-substituted 1,3,5-trinitrohexahydropyrimidines. In all of these studies, the discrepancies in the elemental atom balances were usually within 5%. Insight was gained into the overall decomposition mechanism of these compounds and mixtures. In the cured mixture study, the use of the curing agent HMDI was found to produce a propellant which tended to burn more cleanly than a mixture cured with N-100. The investigation of the aliphatic nitrate esters showed a strong correlation between the oxygen balance and the composition of the gaseous pyrolysis products. However, a study on a group of 5-substituted 1,3,5-trinitrohexahydropyrimidines demonstrated that the thermal decomposition was more affected by the substituent on the 5 position than the oxygen balance. The identity of the substituent seemed to trigger the decomposition, as indicated both by the temperature and gaseous products.