Vaporation characteristics of low-melting nitrocompounds by isothermal thermogravimetry

Determination of vapor pressure is critical for accurate detection of trace volatile hazardous materials, ensuring human health and environmental security. 2,4,6-Trinitrotoluene (TNT), 3,4-Dinitrofurazanfuroxan (DNTF), and 2,4-Dinitroanisole (DNAN) are an important class of volatile low-melting nitrocompounds which are widely used in military, aerospace, and defense industry. In this study, the sublimation and evaporation characteristics of these three nitrocompounds were investigated for the first time by using isothermal thermogravimetry (TG) undergoing zero order, non-activated evaporation processes, analyzed with the Antoine and Langmuir equations, and confirmed with benzoic acid as a calibration material. The Clausius-Clapeyron equations of TNT, DNTF, and DNAN at both sublimation and evaporation processes are established using the temperature dependence of vapor pressure. The enthalpies of sublimation and evaporation are determined. The results of TNT are well consistent with literatures, proving that the isothermal TG for determination of vapor pressure is eligible and accurate. This work lays the foundation for further study of the reliable trace detection of hazardous low-melting nitrocompounds.