Synthesis and Investigation of the Properties of Energetic Ionic Liquids as Fuels of Hypergolic Propellants

The design and synthesis of energetic ionic liquids has provided a new method in the development of a new type of hypergolic propellants. These compounds, having characteristics such as low vapor pressure, high chemical and thermal stability,wide range of liquidity and having environmental requirements, are proposed as fuel substitutes in common liquid propellants that mainly contain hydrazine and its toxic derivatives. In this research, the synthesis of some new symmetric and asymmetric dimidazolium ionic liquids based on the energetic nitrocyanamide anion has been investigated. 1HNMR and FT-IR spectroscopic methods have been used to identify and characterize the synthesized ionic liquids. The viscosity analysis data of these ionic liquids show that in terms of viscosity, they can be used as hypergolic fuels in propellants (viscosity less than 63cP). Among the synthesized energetic ionic liquids, 1-(2-propenyl)-1’-methyl-3,3’-(1,3-propan-di-yl)diimidazolium dinitrocyanamide has the lowest viscosity (42cP). The thermal gravimetric analysis (TGA) of this compound shows its high thermal stability (around 250ºC). Differential scanning calorimetry (DSC) analysis of this material showed a good agreement with TGA analysis data. In addition, the hypergolic properties of the synthesized ionic liquids were investigated in the presence of concentrated nitric acid and it was shown that upon contact with the oxidizer, these materials ignited spontaneously (ID<48ms).