Modification of Vacuum Stability Test for Determination of Decomposition Kinetics
The Vacuum Stability Test (VST) is commonly used test for the evaluation of explosives stability and compatibility. The results obtained from VST can well supply or replace the other stability measurements based on the temperature rise monitoring mostly, e.g. microcallorimetry. Despite the stability evaluation with VST is based on the secondary effects of the decomposition reactions, the obtained results are well comparable in many cases. However VST is mostly used only as a comparative tool. The evacuated sample is heated for prescribed time (typically 2g the of sample are heated at 120C for 40 hours) and the amount of evolved gases is used as a measure of the stability. The modification of measurement conditions and the evaluation of the achieved results by procedures used in the other kinds of the thermal analysis enables to describe the whole decomposition of the sample. Such a modification of VST for the determination of decomposition kinetics of gun propellants is presented in this paper. The pressure of gases evolved during the test is monitored continuously and the measurement is sufficiently long to content the whole decomposition up to the total conversion. The pressure-time function is directly proportional to the reaction progress-time curve. The whole measurement is repeated at several temperatures and the reaction progress-time curves obtained at different temperatures are treated with usual way in thermal analysis. A few methods of the kinetic triplet (activation energy, preexponential factor, reaction model) calculation are described. Based on the comparison of calculated reaction progresses with the measured ones, the connection of the isoconversional method with the nonlinear optimization methods (Nelder-Mead, Levenberg- Marquardt) gives the best results. The description of the sample decomposition with the differential kinetic equation allows to quantitatively predict the rate of decomposition at temperatures profiles different to that used in the test. The obtained kinetic parameters can be easily applied as the input values in the field of numerical simulations. These simulations enable the prediction of the explored substances behavior at arbitrary conditions (temperature, dimensions). The costly and difficult experimental measurements (at real conditions for the prediction of critical parameters necessary for the evaluation of the safety of explored materials) can be complemented or supplied by these simulations. The results of the kinetic triplet estimation for two kinds of gun propellants are presented here.
vacuum stability test decomposition kinetics propellants
Jakub SELESOVSKY Miloslav KRUPKA
University of Pardubice, Faculty of Chemical Technology, Institute of Energetic Materials, 53210 Pardubice, Czech Republic
国际会议
西安
英文
381-385
2007-10-23（万方平台首次上网日期，不代表论文的发表时间）