Thermal Analysis Studies on Isopropylnitrate

Isopropylnitrate (IPN) is described as a detonable material used in propellants and explosives. While there is considerable information available on its sensitivity and compatibility with other materials, very little is known about its thermochemical properties. This paper will describe the results obtained from some DSC, heat flux calorimetry (HFC) and accelerating rate calorimetry (ARC) measurements. The ASTM DSC method using a hermetic aluminum pan having a lid with a laser-produced pin hole was used to determine the vapour pressure of IPN₁. Results calculated from an Antoine equation are in substantial agreement with those determined from DSC measurements. From the latter measurements, the enthalpy of vaporization was determined to be 35.32±0.62 kJ mol⁻¹. Attempts to determine vapour pressures above about 0.8 MPa resulted in significant decomposition of IPN_g. The enthalpy change for decomposition in sealed glass systems was found to be -3.43±0.09 kJ g⁻¹ and -3.85±0.03 kJ g⁻¹, respectively from DSC and HFC measurements on IPN₁ samples loaded in air. Slightly larger exotherms were observed for the HFC results in air than those in inert gas, suggesting some oxidation occurs. In contrast, no significant difference in the observed onset temperature of about 150°C was observed for both the HFC and ARC results. From DSC measurements, an Arrhenius activation energy for decomposition of 126±4 kJ mol⁻¹ was found. These measurements were also conducted in sealed glass systems and decomposition appeared to proceed primarily from the liquid phase. This revised version was published online in August 2006 with corrections to the Cover Date.