The mechanism of the antimony/potassium permanganate combustion reaction

Abstract

Results of a detailed thermoanalytical study of the reactions in the antimony/potassium permanganate system, which has been in use for many years as a delay composition, are presented.The starting points for such a study were the investigation of the thermal decomposition of KMn04, and the oxidation characteristics of the antimony as well as the thermal analysis of the oxides of antimony.Thermal decomposition of freshly prepared crystals and finely powdered KMno 4 were studied utilising thermogravimetry, differential scanning calorimetry and hot stage microsocopy techniques, under atmospheres of air, nitrogen and argon. Data obtained from both TG and DSC analysis were used to measure the non-isothermal decomposition kinetics of KMnO 4. The activation energy was calculated applying a number of different methods, and the results were compared with the isothermal evaluation of activation energy.The decomposition of single crystals of KMn04 was observed under a hot-stage microscope with a particular interest in the fragmentation process, and the mechanism of the decomposition reaction is discussed.The gas-solid oxidation of antimony in air was carried out by both DSC and TG methods. The results revealed a two stage oxidation process corresponding to the surface and bulk oxidation of antimony particles.The reactions of the S b/ KMno 4 systems were investigated extensively in pelleted form as well as in powdered form by the thermoanalytical methods. The ignition reaction of Sb/ KMno 4 mixtures were observed by a microscope as the temperature of the sample increased rapidly. The effect of atmosphere on the occurrence of the ignition reaction was tested. On the basis of the results obtained from thermal analysis and the studies of the mixtures in compacted form, conclusions on the mechanisms of the main propagation reaction were drawn.<br/