Thermal characterization of the CHNO-oxidizer TNEF

The halogen-free CHNO oxidizer TNEF (tris(2.2.2-trinitroethyl) orthoformate) has the potential to replace the oxidizer AP (ammonium perchlorate) in some applications and could improve the environmental impact of composite rocket propellants. The oxygen balance with respect to CO formation based on the carbon content of TNEF is 30.4% and be compared to the values of ammonium perchlorate (AP): 34.0%, ammonium dinitramide (ADN): 25.8%, and hydrazinium ni-troformate (HNF): 21.9%. The impact sensitivity and friction sensitivity of TNEF are 5 Nm and 95 N respectively, which lie within acceptable ranges. Due to the presence of the three trinitroethyl groups in TNEF, the thermal-chemical stability of TNEF may be problematic. To clarify this im-portant aspect, thermal loads at several low and medium temperature conditions (80°C to 100°C and time periods up 40 days) were performed using mass loss, heat generation rate by micro-calorimetry, gas evolution was determined by pressure transducer measurements, and adiabatic self-heating by ARC (adiabatic rate calorimeter). DSC measurements in closed high pressure crucibles at several heating-up rates performed in air as well in argon complement the data in the higher temperature region of TNEF decomposition. The results are evaluated and discussed.