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2 Central European Journal of Energetic Materials

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The Applicability of Chromatographic Methods in the Investigation of Ageing Processes in Double Base Rocket Propellants

Matečić-Muśanić S., Sućeska M., Čuljak R.

Central European Journal of Energetic Materials

2013

Vol. 10, no. 2

245--262

The ageing of double base (DB) rocket propellants is the result of chemical decomposition reactions and physical processes, causing degradation of a number of relevant propellant properties (such as reduction in stabilizer and nitroglycerine (NG) content, reduction of the mean molecular mass of nitrocellulose (NC) etc.), which is refected in a decrease in the reliable service life time of DB propellants. This is the reason why the study of processes of ageing and their consequences (effects) is so important. In this paper we have studied the kinetics of DB rocket propellant decomposition during their artifcial ageing, i.e. at elevated temperatures. The kinetic parameters were obtained by measurements of the stabilizer/Ethyl Centralite (EC) content and the mean molecular mass reduction of NC, during artifcial ageing at temperatures of 80, 85 and 90 °C. Consumption of the EC was observed using High Performance Liquid Chromatography (HPLC), whilst the reduction in the mean molecular mass of NC was monitored using Gel Permeation Chromatography (GPC). It has been shown that artifcial ageing of DB propellant causes signifcant EC consumption and a reduction in the mean molecular mass of NC, from the very beginning of ageing. EC is entirely consumed after 120 days at 80 °C, and is followed by the intensive reactions of NC decomposition. Signifcant changes in the mean molecular mass of NC starts after 60 days of ageing at 90 °C (or ~250 days at 80 °C). The results obtained from the kinetic data have shown that the activation energy of DB propellant decomposition, determined on the basis of changes in the mean molecular mass of NC is 145.09 kJ•mol-1 , whilst the activation energy of decomposition obtained on the basis of EC consumption is 142.98 kJ•mol-1 , which is consistent with available literature values [1, 2].

Numerical Modeling of Self-Ignition of Energetic Materials

Sućeska M., Matečić-Muśanić S.

Central European Journal of Energetic Materials

2004

Vol. 1, nr 1

23-41

Thermal decomposition of energetic materials is accompanied by generation of heat, and under certain conditions may lead to the well-known phenomenon of the self-ignition (or thermal explosion). Therefore, it is of great concern of explosive community to predict whether or not a specimen of energetic material will ignite or not under given conditions (defined primarily by a specimen mass and shape, surrounding temperature, etc.). In order to describe the reactive heat conduction phenomena in an infinite slab, cylindrical, and spherical geometry of an explosive material, an own computer program, based on the thermal explosion theory and the finite difference method, was developed. The program was tested by the comparison of calculated times to ignition for some standard high explosives with times to ignition determined experimentally, as well as with times to ignitions calculated by some other authors. The results of calculations were also compared with the results of calculation according to an analytical solution of the heat balance equation derived by Frank-Kamenetskii. It was found out that not only values of the activation energy and pre-exponential factor, but also the kinetic model of thermal decomposition used in the calculation, have a crucial influence on the results of calculation. It was also shown that the Frank-Kamenetskii equation gives considerably lower values of the times to ignition, and higher values of the critical temperatures for explosives studied.